The exhaust from ships already causes more and brighter clouds above the oceans.Ships churning across the Pacific Ocean left this cluster of bright cloud trails lingering in the atmosphere. The narrow clouds, known as ship tracks,
form when water vapor condenses around tiny particles of pollution that
ships either emit directly as exhaust or that form as a result of gases
within the exhaust.
Marine cloud brightening also known as marine cloud seeding and marine cloud engineering is a proposed solar radiation management technique that would make clouds brighter, reflecting a small fraction of incoming sunlight back into space in order to offset global warming. Along with stratospheric aerosol injection, it is one of the two solar radiation management methods that may most feasibly have a substantial climate impact. The intention is that increasing the Earth's albedo, in combination with greenhouse gas emissions reduction, would reduce climate change and its risks to people and the environment.
If implemented, the cooling effect is expected to be felt rapidly and
to be reversible on fairly short time scales. However, technical
barriers remain to large-scale marine cloud brightening. There are also
risks with such modification of complex climate systems.
Basic principles
Marine
cloud brightening is based on phenomena that are currently observed in
the climate system. Today, emissions particles mix with clouds in the
atmosphere and increase the amount of sunlight they reflect, reducing
warming. This 'cooling' effect is estimated at between 0.5 and 1.5 °C,
and is one of the most important unknowns in climate.
Marine cloud brightening proposes to generate a similar effect using
benign material (e.g. sea salt) delivered to clouds that are most
susceptible to these effects (marine stratocumulus).
Most clouds are quite reflective,
redirecting incoming solar radiation back into space. Increasing
clouds' albedo would increase the portion of incoming solar radiation
that is reflected, in turn cooling the planet. Clouds consist of water
droplets, and clouds with smaller droplets are more reflective (because
of the Twomey effect). Cloud condensation nuclei are necessary for water droplet formation. The central idea underlying marine cloud brightening is to add aerosols to atmospheric locations where clouds form. These would then act as cloud condensation nuclei, increasing the cloud albedo.
Marine cloud brightening on a small scale already occurs unintentionally due to the aerosols in ships' exhaust, leaving ship tracks.
Changes to shipping regulations in enacted by the United Nations’
International Maritime Organization (IMO) to reduce certain aerosols are
hypothesized to be leading to reduced cloud cover and increased oceanic
warming, providing additional support to the potential effectiveness of
marine cloud brightening at modifying ocean temperature. Different cloud regimes are likely to have differing susceptibility to brightening strategies, with marine stratocumulus clouds (low, layered clouds over ocean regions) most sensitive to aerosol changes.
These marine stratocumulus clouds are thus typically proposed as the
suited target. They are common over the cooler regions of subtropical
and midlatitude oceans, where their coverage can exceed 50% in the
annual mean.
The leading possible source of additional cloud condensation nuclei is salt from seawater, although there are others.
Even though the importance of aerosols for the formation of
clouds is, in general, well understood, many uncertainties remain. In
fact, the latest IPCC report considers aerosol-cloud interactions as one of the current major challenges in climate modeling in general. In particular, the number of droplets does not increase proportionally when more aerosols are present and can even decrease.
Extrapolating the effects of particles on clouds observed on the
microphysical scale to the regional, climatically relevant scale, is not
straightforward.
Climatic impacts
Reduction in global warming
The modeling evidence of the global climatic effects of marine cloud brightening remains limited.
Current modeling research indicates that marine cloud brightening could
substantially cool the planet. One study estimated that it could
produce 3.7 W/m2 of globally averaged negative forcing. This would counteract the warming caused by a doubling of the preindustrial atmospheric carbon dioxide concentration, or an estimated 3 degrees Celsius, although models have indicated less capacity.
A 2020 study found a substantial increase in cloud reflectivity from
shipping in southeast Atlantic basin, suggesting that a regional-scale
test of MCB in stratocumulus‐dominated regions could be successful.
The climatic impacts of marine cloud brightening would be rapidly
responsive and reversible. If the brightening activity were to change
in intensity, or stop altogether, then the clouds' brightness would
respond within a few days to weeks, as the cloud condensation nuclei
particles precipitate naturally.
Again unlike stratospheric aerosol injection, marine cloud
brightening might be able to be used regionally, albeit in a limited
manner.
Marine stratocumulus clouds are common in particular regions,
specifically the eastern Pacific Ocean and the eastern South Atlantic
Ocean. A typical finding among simulation studies was a persistent
cooling of the Pacific, similar to the “La NiƱa” phenomenon, and,
despite the localized nature of the albedo change, an increase in polar
sea ice. Recent studies aim at making simulation findings derived from different models comparable.
Side effects
There is some potential for changes to precipitation patterns and amplitude,
although modeling suggests that the changes are likely less than those
for stratospheric aerosol injection and considerably smaller than for
unabated anthropogenic global warming.
Regional implementations of MCB would need care to avoid causing
possibly adverse consequences in areas far away from the region they are
aiming to help. For example, a potential Marine Cloud Brightening aimed
at cooling Western United States could risk causing increasing heat in
Europe, due to climate teleconnections such as unintended perturbation of the Atlantic meridional overturning circulation.
Research
Marine cloud brightening was originally suggested by John Latham in 1990.
Because clouds remain a major source of uncertainty in climate
change, some research projects into cloud reflectivity in the general
climate change context have provided insight into marine cloud
brightening specifically. For example, one project released smoke behind
ships in the Pacific Ocean and monitored the particulates' impact on
clouds.
Although this was done in order to better understand clouds and climate
change, the research has implications for marine cloud brightening.
A research coalition called the Marine Cloud Brightening Project
was formed in order to coordinate research activities. Its proposed
program includes modeling, field experiments, technology development and
policy research to study cloud-aerosol effects and marine cloud
brightening. The proposed program currently serves as a model for
process-level (environmentally benign) experimental programs in the
atmosphere. Formed in 2009 by Kelly Wanser with support from Ken Caldeira,
the project is now housed at the University of Washington. Its
co-principals are Robert Wood, Thomas Ackerman, Philip Rasch, Sean
Garner (PARC), and Kelly Wanser (Silver Lining). The project is managed
by Sarah Doherty.
The shipping industry may have been carrying out an unintentional
experiment in marine cloud brightening due to the emissions of ships
and causing a global temperature reduction of as much as 0.25 ˚C lower
than they would otherwise have been.
A 2020 study found a substantial increase in cloud reflectivity from
shipping in southeast Atlantic basin, suggesting that a regional-scale
test of MCB in stratocumulus‐dominated regions could be successful.
Marine cloud brightening is being examined as a way to shade and cool coral reefs such as the Great Barrier Reef.
Proposed methods
The
leading proposed method for marine cloud brightening is to generate a
fine mist of salt from seawater, and to deliver into targeted banks of
marine stratocumulus clouds from ships traversing the ocean. This
requires technology that can generate optimally-sized (~100 nm) sea-salt
particles and deliver them at sufficient force and scale to penetrate
low-lying marine clouds. The resulting spray mist must then be
delivered continuously into target clouds over the ocean.
In the earliest published studies, John Latham and Stephen Salter proposed a fleet of around 1500 unmanned Rotor ships, or Flettner ships, that would spray mist created from seawater into the air.
The vessels would spray sea water droplets at a rate of approximately
50 cubic meters per second over a large portion of Earth's ocean
surface. The power for the rotors and the ship could be generated from
underwater turbines. Salter and colleagues proposed using active hydro
foils with controlled pitch for power.
Subsequent researchers determined that transport efficiency was
only relevant for use at scale, and that for research requirements,
standard ships could be used for transport. (Some researchers considered
aircraft as an option, but concluded that it would be too costly.)
Droplet generation and delivery technology is critical to progress, and
technology research has been focused on solving this challenging
problem.
Other methods were proposed and discounted, including:
Using small droplets of seawater into the air through ocean
foams. When bubbles in the foams burst, they loft small droplets of
seawater.
Using piezoelectric transducer. This would create faraday waves
at a free surface. If the waves are steep enough, droplets of sea water
will be thrown from the crests and the resulting salt particles can
enter into the clouds. However, a significant amount of energy is
required.
Electrostatic atomization of seawater drops. This technique would
utilize mobile spray platforms that move to adjust to changing weather
conditions. These too could be on unmanned ships.
Using engine or smoke emissions as a source for CCN. Paraffin oil particles have also been proposed, though their viability has been discounted.
Costs
The
costs of marine cloud brightening remain largely unknown. One academic
paper implied annual costs of approximately 50 to 100 million UK pounds (roughly 75 to 150 million US dollars). A report of the US National Academies suggested roughly five billion US dollars annually for a large deployment program (reducing radiative forcing by 5 W/m2).
Marine cloud brightening would be governed primarily by international law because it would likely take place outside of countries' territorial waters, and because it would affect the environment of other countries and of the oceans. For the most part, the international law governing solar radiation management in general would apply. For example, according to customary international law,
if a country were to conduct or approve a marine cloud brightening
activity that would pose significant risk of harm to the environments of
other countries or of the oceans, then that country would be obligated
to minimize this risk pursuant to a due diligence
standard. In this, the country would need to require authorization for
the activity (if it were to be conducted by a private actor), perform a
prior environmental impact assessment, notify and cooperate with potentially affected countries, inform the public, and develop plans for a possible emergency.
Marine cloud brightening activities would be furthered governed by the international law of sea, and particularly by the United Nations Convention on the Law of the Sea
(UNCLOS). Parties to the UNCLOS are obligated to "protect and preserve
the marine environment," including by preventing, reducing, and
controlling pollution of the marine environment from any source. The "marine environment" is not defined but is widely interpreted as including the ocean's water, lifeforms, and the air above. "Pollution of the marine environment" is defined in a way that includes global warming and greenhouse gases.
The UNCLOS could thus be interpreted as obligating the involved Parties
to use methods such as marine cloud brightening if these were found to
be effective and environmentally benign. Whether marine cloud
brightening itself could be such pollution of the marine environment is
unclear. At the same time, in combating pollution, Parties are "not to
transfer, directly or indirectly, damage or hazards from one area to
another or transform one type of pollution into another."
If marine cloud brightening were found to cause damage or hazards, the
UNCLOS could prohibit it. If marine cloud brightening activities were to
be "marine scientific research"—also an undefined term—then UNCLOS
Parties have a right to conduct the research, subject to some
qualifications.
Like all other ships, those that would conduct marine cloud brightening
must bear the flag of the country that has given them permission to do
so and to which the ship has a genuine link, even if the ship is
unmanned or automated. The flagged state must exercise its jurisdiction over those ships. The legal implications would depend on, among other things, whether the activity were to occur in territorial waters, an exclusive economic zone (EEZ), or the high seas;
and whether the activity was scientific research or not. Coastal states
would need to approve any marine cloud brightening activities in their
territorial waters. In the EEZ, the ship must comply with the coastal
state's laws and regulations.
It appears that the state conducting marine cloud brightening
activities in another state's EEZ would not need the latter's
permission, unless the activity were marine scientific research. In that
case, the coastal state should grant permission in normal
circumstances.
States would be generally free to conduct marine cloud brightening
activities on the high seas, provided that this is done with "due
regard" for other states' interests. There is some legal unclarity
regarding unmanned or automated ships.
Advantages and disadvantages
Marine cloud brightening appears to have most of the advantages and disadvantages of solar radiation management
in general. For example, it presently appears to be inexpensive
relative to suffering climate change damages and greenhouse gas
emissions abatement, fast acting, and reversible in its direct climatic
effects. Some advantages and disadvantages are specific to it, relative
to other proposed solar radiation management techniques.
Compared with other proposed solar radiation management methods, such as stratospheric aerosols injection, marine cloud brightening may be able to be partially localized in its effects. This could, for example, be used to stabilize the West Antarctic Ice Sheet.
Furthermore, marine cloud brightening, as it is currently envisioned,
would use only natural substances sea water and wind, instead of
introducing human-made substances into the environment.
Potential disadvantages include that specific MCB implementations
could have a varying effect across time; the same intervention might
even become a net contributor to global warming some years after being
first launched, though this could be avoided with careful planning.
Chronic subcortical electrode implant in a laboratory rat used to deliver electrical stimulation to the brain.
Remote control animals are animals that are controlled remotely by humans. Some applications require electrodes to be implanted
in the animal's nervous system connected to a receiver which is usually
carried on the animal's back. The animals are controlled by the use of
radio signals. The electrodes do not move the animal directly, as if
controlling a robot; rather, they signal a direction or action desired
by the human operator and then stimulate the animal's reward centres if
the animal complies. These are sometimes called bio-robots or robo-animals. They can be considered to be cyborgs as they combine electronic devices with an organic life form and hence are sometimes also called cyborg-animals or cyborg-insects.
Because of the surgery required, and the moral and ethical issues
involved, there has been criticism aimed at the use of remote control
animals, especially regarding animal welfare and animal rights, especially when relatively intelligent complex animals are used. Non-invasive
applications may include stimulation of the brain with ultrasound to
control the animal. Some applications (used primarily for dogs) use
vibrations or sound to control the movements of the animals.
Remote control animals can be directed and used as working animals for search and rescue operations, covert reconnaissance, data-gathering in hazardous areas, or various other uses.
Mammals
Rats
Several
studies have examined the remote control of rats using micro-electrodes
implanted into their brains and rely on stimulating the reward centre of the rat. Three electrodes are implanted; two in the ventral posterolateral nucleus of the thalamus which conveys facial sensory information from the left and right whiskers, and a third in the medial forebrain bundle which is involved in the reward process of the rat. This third electrode is used to give a rewarding electrical stimulus
to the brain when the rat makes the correct move to the left or right.
During training, the operator stimulates the left or right electrode of
the rat making it "feel" a touch to the corresponding set of whiskers,
as though it had come in contact with an obstacle. If the rat then makes
the correct response, the operator rewards the rat by stimulating the
third electrode.
In 2002, a team of scientists at the State University of New York
remotely controlled rats from a laptop up to 500 m away. The rats could
be instructed to turn left or right, climb trees and ladders, navigate
piles of rubble, and jump from different heights. They could even be
commanded into brightly lit areas, which rats usually avoid. It has been
suggested that the rats could be used to carry cameras to people
trapped in disaster zones.
In 2013, researchers reported the development of a
radio-telemetry system to remotely control free-roaming rats with a
range of 200 m. The backpack worn by the rat includes the mainboard and
an FM
transmitter-receiver, which can generate biphasic microcurrent pulses.
All components in the system are commercially available and are
fabricated from surface mount devices to reduce the size (25 x 15 x 2 mm) and weight (10 g with battery).
Ethics and welfare concerns
Concerns have been raised about the ethics of such studies. Even one of the pioneers in this area of study, Sanjiv Talwar,
said "There's going to have to be a wide debate to see whether this is
acceptable or not" and "There are some ethical issues here which I can't
deny." Elsewhere he was quoted as saying "The idea sounds a little creepy."
Some oppose the idea of placing living creatures under direct human
command. "It's appalling, and yet another example of how the human
species instrumentalises other species," says Gill Langley of the Dr Hadwen Trust based in Hertfordshire (UK), which funds alternatives to animal-based research. Gary Francione, an expert in animal welfare law at Rutgers University School of Law, says "The animal is no longer functioning as an animal," as the rat is operating under someone's control.
And the issue goes beyond whether or not the stimulations are
compelling or rewarding the rat to act. "There's got to be a level of
discomfort in implanting these electrodes," he says, which may be
difficult to justify. Talwar stated that the animal's "native
intelligence" can stop it from performing some directives but with
enough stimulation, this hesitation can sometimes be overcome, but
occasionally cannot.
Non-invasive method
Researchers at Harvard University have created a brain-to-brain interface (BBI) between a human and a Sprague-Dawley rat. Simply by thinking the appropriate thought, the BBI allows the human to control the rat's tail. The human wears an EEG-based
brain-to-computer interface (BCI), while the anesthetised rat is
equipped with a focused ultrasound (FUS) computer-to-brain interface
(CBI). FUS is a technology that allows the researchers to excite a
specific region of neurons in the rat's brain using an ultrasound signal
(350 kHz ultrasound frequency, tone burst duration of 0.5 ms, pulse
repetition frequency of 1 kHz, given for 300 ms duration). The main
advantage of FUS is that, unlike most brain-stimulation techniques, it
is non-invasive. Whenever the human looks at a specific pattern (strobe
light flicker) on a computer screen, the BCI communicates a command to
the rat's CBI, which causes ultrasound to be beamed into the region of
the rat's motor cortex
responsible for tail movement. The researchers report that the human
BCI has an accuracy of 94%, and that it generally takes around 1.5 s
from the human looking at the screen to movement of the rat's tail.
Another system that non-invasively controls rats uses ultrasonic, epidermal and LED
photic stimulators on the back. The system receives commands to deliver
specified electrical stimulations to the hearing, pain and visual
senses of the rat respectively. The three stimuli work in groups for the
rat navigation.
Other researchers have dispensed with human remote control of rats and instead uses a General Regression Neural Network algorithm to analyse and model controlling of human operations.
Dogs
Dogs
are often used in disaster relief, at crime scenes and on the
battlefield, but it's not always easy for them to hear the commands of
their handlers. A command module which contains a microprocessor, wireless radio, GPS receiver and an attitude and heading reference system (essentially a gyroscope)
can be fitted to dogs. The command module delivers vibration or sound
commands (delivered by the handler over the radio) to the dog to guide
it in a certain direction or to perform certain actions. The overall
success rate of the control system is 86.6%.
Mice
Researchers
responsible for developing remote control of a pigeon using brain
implants conducted a similar successful experiment on mice in 2005.
Invertebrates
In 1967, Franz Huber pioneered electrical stimulation to the brain of insects and showed that mushroom body stimulation elicits complex behaviours, including the inhibition of locomotion.
Cockroaches
Rechargeable cyborg insects with an ultrasoft organic solar cell moduleFundamental behavioural ability with electronics in cyborg insects
RoboRoach
The US-based company Backyard Brains released the "RoboRoach", a
remote controlled cockroach kit that they refer to as "The world's first
commercially available cyborg". The project started as a University of Michigan biomedical engineering student senior design project in 2010 and was launched as an available beta product on 25 February 2011. The RoboRoach was officially released into production via a TED talk at the TED Global conference, and via the crowdsourcing website Kickstarter in 2013, the kit allows students to use microstimulation to momentarily control the movements of a walking cockroach (left and right) using a bluetooth-enabled smartphone
as the controller. The RoboRoach was the first kit available to the
general public for the remote control of an animal and was funded by the
United States' National Institute of Mental Health as a device to serve as a teaching aid to promote an interest in neuroscience.
This funding was due to the similarities between the RoboRoach
microstimulation, and the microstimulation used in the treatments of Parkinson's disease (Deep Brain Stimulation) and deafness (Cochlear implants) in humans. Several animal welfare organizations including the RSPCA and PETA have expressed concerns about the ethics and welfare of animals in this project.
North Carolina State University
Another group at North Carolina State University
has developed a remote control cockroach. Researchers at NCSU have
programmed a path for cockroaches to follow while tracking their
location with an XboxKinect. The system automatically adjusted the cockroach's movements to ensure it stayed on the prescribed path.
Robo-bug
In 2022, researchers led by RIKEN scientists, reported the development of remote controlled cyborg cockroaches
functional if moved (or moving) to sunlight for recharging. They could
be used e.g. for purposes of inspecting hazardous areas or quickly
finding humans underneath hard-to-access rubbles at disaster sites.
Beetles
Cyborg beetles developed based on Zophobas morio (left) and Mecynorrhina torquata (right)
In 2009, remote control of the flight movements of the Cotinus texana and the much larger Mecynorrhina torquata beetles has been achieved during experiments funded by the Defence Advanced Research Projects Agency
(DARPA). The weight of the electronics and battery meant that only
Mecynorrhina was strong enough to fly freely under radio control. A
specific series of pulses sent to the optic lobes
of the insect encouraged it to take flight. The average length of
flights was just 45 seconds, although one lasted for more than 30
minutes. A single pulse caused the beetle to land again. Stimulation of basilar flight muscles
allowed the controller to direct the insect left or right, although
this was successful on only 75% of stimulations. After each maneuver,
the beetles quickly righted themselves and continued flying parallel to
the ground. In 2015, researchers was able to fine tune the beetle
steering in flight by changing the pulse train applied on the
wing-folding muscle.Recently, scientists from Nanyang Technological University, Singapore,
have demonstrated graded turning and backward walking in a small
darkling beetle (Zophobas morio), which is 2 cm to 2.5 cm long and
weight only 1 g including the electronic backpack and battery.
It has been suggested the beetles could be used for search and rescue
mission, however, it has been noted that currently available batteries,
solar cells and piezoelectrics that harvest energy from movement cannot provide enough power to run the electrodes and radio transmitters for very long.
Work using Drosophila
has dispensed with stimulating electrodes and developed a 3-part remote
control system that evokes action potentials in pre-specified Drosophila neurons using a laser beam. The central component of the remote control system is a Ligand-gated ion channel gated by ATP. When ATP is applied, uptake of external calcium is induced and action potentials generated. The remaining two parts of the remote control system include chemically caged ATP, which is injected into the central nervous system
through the fly's simple eye, and laser light capable of uncaging the
injected ATP. The giant fibre system in insects consists of a pair of
large interneurons in the brain which can excite the insect flight and
jump muscles. A 200 ms pulse of laser light elicited jumping, wing
flapping, or other flight movements in 60%–80% of the flies. Although
this frequency is lower than that observed with direct electrical
stimulation of the giant fibre system, it is higher than that elicited
by natural stimuli, such as a light-off stimulus.
Fish
Sharks
Spiny dogfish sharks
have been remotely controlled by implanting electrodes deep in the
shark's brain to a remote control device outside the tank. When an
electric current is passed through the wire, it stimulates the shark's
sense of smell and the animal turns, just as it would move toward blood
in the ocean. Stronger electrical signals—mimicking stronger
smells—cause the shark to turn more sharply. One study is funded by a
$600,000 grant from Defense Advanced Research Projects Agency (DARPA).
It has been suggested that such sharks could search hostile waters with
sensors that detect explosives, or cameras that record intelligence
photographs. Outside the military, similar sensors could detect oil
spills or gather data on the behaviour of sharks in their natural
habitat. Scientists working with remote control sharks admit they are
not sure exactly which neurons they are stimulating, and therefore, they
can't always control the shark's direction reliably. The sharks only
respond after some training, and some sharks don't respond at all. The
research has prompted protests from bloggers who allude to remote
controlled humans or horror films featuring maniacal cyborg sharks on a
feeding frenzy.
An alternative technique was to use small gadgets attached to the shark's noses that released squid juice on demand.
Reptiles
Turtles
South Korean researchers have remotely controlled the movements of a turtle using a completely non-invasive steering system. Red-eared terrapins (Trachemys scripta elegans)
were made to follow a specific path by manipulating the turtles'
natural obstacle avoidance behaviour. If these turtles detect something
is blocking their path in one direction, they move to avoid it. The
researchers attached a black half cylinder to the turtle. The "visor"
was positioned around the turtle's rear end, but was pivoted around
using a microcontroller and a servo
motor to either the left or right to partially block the turtle's
vision on one side. This made the turtle believe there was an obstacle
it needed to avoid on that side and thereby encouraged the turtle to
move in the other direction.
Geckos
Some
animals have had parts of their bodies remotely controlled, rather than
their entire bodies. Researchers in China stimulated the mesencephalon of geckos (G. gecko)
via micro stainless steel electrodes and observed the gecko's responses
during stimulation. Locomotion responses such as spinal bending and
limb movements could be elicited in different depths of mesencephalon.
Stimulation of the periaqueductal gray area elicited ipsilateral spinal bending while stimulation of the ventral tegmental area elicited contralateral spinal bending.
Birds
Pigeons
In
2007, researchers at east China's Shandong University of Science and
Technology implanted micro electrodes in the brain of a pigeon so they
could remotely control it to fly right or left, or up or down.
Uses and justification
Remote-controlled
animals are considered to have several potential uses, replacing the
need for humans in some dangerous situations. Their application is
further widened if they are equipped with additional electronic devices.
Small creatures fitted with cameras and other sensors have been
proposed as being useful when searching for survivors after a building
has collapsed, with cockroaches or rats being small and manoeuvrable
enough to go under rubble.
There have been a number of suggested military uses of remote controlled animals, particularly in the area of surveillance. Remote-controlled dogfish sharks have been likened to the studies into the use of military dolphins. It has also been proposed that remote-controlled rats could be used for the clearing of land mines.
Other suggested fields of application include pest control, the mapping
of underground areas, and the study of animal behaviour.
Development of robots that are capable of performing the same
actions as controlled animals is often technologically difficult and
cost-prohibitive.
Flight is very difficult to replicate while having an acceptable
payload and flight duration. Harnessing insects and using their natural
flying ability gives significant improvements in performance.
The availability of "inexpensive, organic substitutes" therefore allows
for the development of small, controllable robots that are otherwise
currently unavailable.
Similar applications
Some
animals are remotely controlled, but rather than being directed to move
left or right, the animal is prevented from moving forward, or its
behaviour is modified in other ways.
Shock collars deliver electrical shocks of varying intensity and
duration to the neck or other area of a dog's body via a
radio-controlled electronic device incorporated into a dog collar. Some
collar models also include a tone or vibration setting, as an
alternative to or in conjunction with the shock. Shock collars are now
readily available and have been used in a range of applications,
including behavioural modification, obedience training, and pet
containment, as well as in military, police and service training. While
similar systems are available for other animals, the most common are
the collars designed for domestic dogs.
The use of shock collars is controversial and scientific evidence for their safety and efficacy is mixed.
A few countries have enacted bans or controls on their use. Some animal
welfare organizations warn against their use or actively support a ban
on their use or sale.
Some want restrictions placed on their sale. Some professional dog
trainers and their organizations oppose their use and some support them.
Support for their use or calls for bans from the general public is
mixed.
In 2007, it was reported that scientists at the Commonwealth Scientific and Industrial Research Organisation had developed a prototype "invisible fence" using the Global Positioning System
(GPS) in a project nicknamed Bovines Without Borders. The system uses
battery-powered collars that emit a sound to warn cattle when they are
approaching a virtual boundary. If a cow wanders too near, the collar
emits a warning noise. If it continues, the cow gets an electric shock
of 250-milliwatts . The boundaries are drawn by GPS and exist only as a
line on a computer. There are no wires or fixed transmitters at all. The
cattle took less than an hour to learn to back off when they heard the
warning noise. The scientists indicated that commercial units were up to
10 years away.
Another type of invisible fence uses a buried wire that sends
radio signals to activate shock collars worn by animals that are
"fenced" in. The system works with three signals. The first is visual
(white plastic flags spaced at intervals around the perimeter in the
fenced-in area), the second is audible (the collar emits a sound when
the animal wearing it approaches buried cable), and finally there's an
electric shock to indicate they have reached the fence.
Other invisible fences are wireless. Rather than using a buried
wire, they emit a radio signal from a central unit, and activate when
the animal travels beyond a certain radius from the unit.
Afghanistan,
Canada, China, Colombia, India, Jamaica, Lebanon, Mexico, Morocco,
Netherlands, Pakistan, Paraguay, Spain, Thailand, Turkey, United
Kingdom, United States
Cannabis has various mental and physical effects, which include euphoria, altered states of mind and sense of time, difficulty concentrating, impaired short-term memory, impaired body movement (balance and fine psychomotor control), relaxation, and an increase in appetite.
Onset of effects is felt within minutes when smoked, but may take up to
90 minutes when eaten (as orally consumed drugs must be digested and
absorbed). The effects last for two to six hours, depending on the
amount used. At high doses, mental effects can include anxiety, delusions (including ideas of reference), hallucinations, panic, paranoia, and psychosis. There is a strong relation between cannabis use and the risk of psychosis, though the direction of causality
is debated. Physical effects include increased heart rate, difficulty
breathing, nausea, and behavioral problems in children whose mothers
used cannabis during pregnancy; short-term side effects may also include
dry mouth and red eyes. Long-term adverse effects may include addiction, decreased mental ability in those who started regular use as adolescents, chronic coughing, susceptibility to respiratory infections, and cannabinoid hyperemesis syndrome.
Cannabis is mostly used recreationally or as a medicinal drug,
although it may also be used for spiritual purposes. In 2013, between
128 and 232 million people used cannabis (2.7% to 4.9% of the global
population between the ages of 15 and 65). It is the most commonly used
largely-illegal drug in the world, with the highest use among adults in Zambia, the United States, Canada, and Nigeria. Since the 1970s, the potency of illicit cannabis has increased, with THC levels rising and CBD levels dropping.
Cannabis plants have been grown since at least the 3rd millennium
BCE and there is evidence of it being smoked for its psychoactive
effects around 500 BCE in the Pamir Mountains,
Central Asia. Since the 14th century, cannabis has been subject to
legal restrictions. The possession, use, and cultivation of cannabis has
been illegal in most countries since the 20th century. In 2013, Uruguay became the first country to legalize recreational use of cannabis. Other countries to do so are Canada, Georgia, Germany, Luxembourg, Malta, South Africa, and Thailand. In the U.S., the recreational use of cannabis is legalized in 24 states, 3 territories, and the District of Columbia, though the drug remains federally illegal. In Australia, it is legalized only in the Australian Capital Territory.
Example of a container and the recreational cannabis purchase in Canada
Medical cannabis, or medical marijuana, refers to the use of cannabis
to treat disease or improve symptoms; however, there is no single
agreed-upon definition (e.g., cannabinoids derived from cannabis and synthetic cannabinoids are also used).
The rigorous scientific study of cannabis as a medicine has been
hampered by production restrictions and by the fact that it is
classified as an illegal drug by many governments. There is some evidence suggesting cannabis can be used to reduce nausea and vomiting during chemotherapy, to improve appetite in people with HIV/AIDS, or to treat chronic pain and muscle spasms. Evidence for its use for other medical applications is insufficient for drawing conclusions about safety or efficacy.
There is evidence supporting the use of cannabis or its derivatives in
the treatment of chemotherapy-induced nausea and vomiting, neuropathic
pain, and multiple sclerosis. Lower levels of evidence support its use
for AIDS wasting syndrome, epilepsy, rheumatoid arthritis, and glaucoma.
The medical use of cannabis is legal only in a limited number of territories, including Canada, Belgium, Australia, the Netherlands, New Zealand, Spain, and many U.S. states. This usage generally requires a prescription, and distribution is usually done within a framework defined by local laws.
Recreational
According to DEA Chief Administrative Law Judge, Francis Young,
"cannabis is one of the safest therapeutically active substances known
to man". Being under the effects of cannabis is usually referred to as being "high". Cannabis consumption has both psychoactive and physiological effects.
The "high" experience can vary widely, based (among other things) on
the user's prior experience with cannabis, and the type of cannabis
consumed. When smoking cannabis, a euphoriant effect can occur within minutes of smoking.
Aside from a subjective change in perception and mood, the most common
short-term physical and neurological effects include increased heart
rate, increased appetite, impairment of short-term and working memory,
and impairment of psychomotor coordination.
Cannabis has held sacred status in several religions and has served as an entheogen – a chemical substance used in religious, shamanic, or spiritual contexts – in the Indian subcontinent since the Vedic period. The earliest known reports regarding the sacred status of cannabis in the Indian subcontinent come from the Atharva Veda, estimated to have been composed sometime around 1400 BCE.
The Hindu god Shiva is described as a cannabis user, known as the "Lord of bhang".
In modern culture, the spiritual use of cannabis has been spread by the disciples of the Rastafari movement who use cannabis as a sacrament and as an aid to meditation.
A joint prior to rolling, with a paper handmade filter on the left
Many different ways to consume cannabis involve heat to decarboxylateTHCA into THC;common modes include:
Smoking, involves burning and inhaling cannabinoids ("smoke") from small pipes, bongs (portable versions of hookahs with a water chamber), paper-wrapped joints, tobacco-leaf-wrapped blunts, or the like.
Vaporizing, heating various forms of cannabis to 165–190 °C (329–374 °F), causing the active ingredients to form vapor without combustion of the plant material (the boiling point of THC is 157 °C (315 °F) at atmospheric pressure).
Edibles,
adding cannabis as an ingredient to a wide variety of foods, including
butter and baked goods. In India it is commonly consumed as the beverage
bhang.
Cannabis tea, prepared with attention to the lipophilic quality of THC, which is only slightly water-soluble (2.8 mg per liter), often involving cannabis in a saturated fat.
In 2013, between 128 and 232 million people used cannabis (2.7% to 4.9% of the global population between the ages of 15 and 65). Cannabis is by far the most widely used illicit substance, with the highest use among adults (as of 2018) in Zambia, the United States, Canada, and Nigeria.
United States
Between 1973 and 1978, eleven states decriminalized marijuana. In 2001, Nevada
reduced marijuana possession to a misdemeanor and since 2012, several
other states have decriminalized and even legalized marijuana.
In 2018, surveys indicated that almost half of the people in the
United States had tried marijuana, 16% had used it in the past year, and
11% had used it in the past month.
In 2014, surveys said daily marijuana use amongst US college students
had reached its highest level since records began in 1980, rising from
3.5% in 2007 to 5.9% in 2014 and had surpassed daily cigarette use.
In the US, men are over twice as likely to use marijuana as
women, and 18–29-year-olds are six times more likely to use as
over-65-year-olds. In 2015, a record 44% of the US population has tried marijuana in their lifetime, an increase from 38% in 2013 and 33% in 1985.
Marijuana use in the United States is three times above the
global average, but in line with other Western democracies. Forty-four
percent of American 12th graders have tried the drug at least once, and
the typical age of first-use is 16, similar to the typical age of
first-use for alcohol but lower than the first-use age for other illicit
drugs.
A 2022 Gallup poll concluded Americans are smoking more marijuana than cigarettes for the first time.
Acute negative effects may include anxiety and panic, impaired attention and memory, an increased risk of psychotic symptoms, the inability to think clearly, and an increased risk of accidents. Cannabis impairs a person's driving ability, and THC
was the illicit drug most frequently found in the blood of drivers who
have been involved in vehicle crashes. Those with THC in their system
are from three to seven times more likely to be the cause of the
accident than those who had not used either cannabis or alcohol,
although its role is not necessarily causal because THC stays in the
bloodstream for days to weeks after intoxication.
Some immediate undesired side effects include a decrease in
short-term memory, dry mouth, impaired motor skills, reddening of the
eyes, dizziness, feeling tired and vomiting. Some users may experience an episode of acute psychosis, which usually abates after six hours, but in rare instances, heavy users may find the symptoms continuing for many days.
Legalization has increased the rates at which children are
exposed to cannabis, particularly from edibles. While the toxicity and
lethality of THC in children is not known, they are at risk for
encephalopathy, hypotension, respiratory depression severe enough to
require ventilation, somnolence and coma.
Fatality
There is no clear evidence for a link between cannabis use and deaths
from cardiovascular disease, but a 2019 review noted that it may be an
under-reported, contributory factor or direct cause in cases of sudden death, due to the strain it can place on the cardiovascular system. Some deaths have also been attributed to cannabinoid hyperemesis syndrome. There is an association between cannabis use and suicide, particularly in younger users.
A 16-month survey of Oregon and Alaska emergency departments
found a report of the death of an adult who had been admitted for acute
cannabis toxicity.
Addiction
experts in psychiatry, chemistry, pharmacology, forensic science,
epidemiology, and the police and legal services engaged in delphic analysis
regarding 20 popular recreational drugs. Cannabis was ranked 11th in
dependence, 17th in physical harm, and 10th in social harm.
Psychological effects
A 2015 meta-analysis found that, although a longer period of
abstinence was associated with smaller magnitudes of impairment, both
retrospective and prospective
memory were impaired in cannabis users. The authors concluded that
some, but not all, of the deficits associated with cannabis use were
reversible.
A 2012 meta-analysis found that deficits in most domains of cognition
persisted beyond the acute period of intoxication, but was not evident
in studies where subjects were abstinent for more than 25 days.
Few high quality studies have been performed on the long-term effects
of cannabis on cognition, and the results were generally inconsistent. Furthermore, effect sizes of significant findings were generally small. One review concluded that, although most cognitive faculties were unimpaired by cannabis use, residual deficits occurred in executive functions.
Impairments in executive functioning are most consistently found in
older populations, which may reflect heavier cannabis exposure, or
developmental effects associated with adolescent cannabis use. One review found three prospective cohort studies that examined the relationship between self-reported cannabis use and intelligence quotient
(IQ). The study following the largest number of heavy cannabis users
reported that IQ declined between ages 7–13 and age 38. Poorer school
performance and increased incidence of leaving school early were both
associated with cannabis use, although a causal relationship was not
established. Cannabis users demonstrated increased activity in task-related brain regions, consistent with reduced processing efficiency.
A reduced quality of life
is associated with heavy cannabis use, although the relationship is
inconsistent and weaker than for tobacco and other substances. The direction of cause and effect, however, is unclear.
Although global abnormalities in white matter and grey matter are not consistently associated with cannabis use, reduced hippocampal volume is consistently found. Amygdala abnormalities are sometimes reported, although findings are inconsistent.
Cannabis use is associated with increased recruitment of task-related areas, such as the dorsolateral prefrontal cortex, which is thought to reflect compensatory activity due to reduced processing efficiency. Cannabis use is also associated with downregulation of CB1
receptors. The magnitude of down regulation is associated with
cumulative cannabis exposure, and is reversed after one month of
abstinence. There is limited evidence that chronic cannabis use can reduce levels of glutamate metabolites in the human brain.
About 9% of those who experiment with marijuana eventually become dependent according to DSM-IV (1994) criteria. A 2013 review estimates daily use is associated with a 10–20% rate of dependence. The highest risk of cannabis dependence is found in those with a history of poor academic achievement, deviant behavior in childhood and adolescence, rebelliousness, poor parental relationships, or a parental history of drug and alcohol problems.
Of daily users, about 50% experience withdrawal upon cessation of use
(i.e. are dependent), characterized by sleep problems, irritability,
dysphoria, and craving. Cannabis withdrawal is less severe than withdrawal from alcohol.
According to DSM-V criteria, 9% of those who are exposed to cannabis develop cannabis use disorder, compared to 20% for cocaine, 23% for alcohol and 68% for nicotine.
Cannabis use disorder in the DSM-V involves a combination of DSM-IV
criteria for cannabis abuse and dependence, plus the addition of
craving, without the criterion related to legal troubles.
From a clinical perspective, two significant school of thought exists
for psychiatric conditions associated with cannabis (or cannabinoids)
use: transient, non-persistent psychotic reactions, and longer-lasting,
persistent disorders that resemble schizophrenia. The former is formally
known as acute cannabis-associated psychotic symptoms (CAPS).
At an epidemiological level, a dose–response relationship exists between cannabis use and increased risk of psychosis and earlier onset of psychosis. Although the epidemiological association is robust, evidence to prove a causal relationship is lacking.
Cannabis may also increase the risk of depression, but insufficient research has been performed to draw a conclusion. Cannabis use is associated with increased risk of anxiety disorders, although causality has not been established.
A review in 2019 found that research was insufficient to
determine the safety and efficacy of using cannabis to treat
schizophrenia, psychosis, or other mental disorders.
Another found that cannabis during adolescence was associated with an
increased risk of developing depression and suicidal behavior later in
life, while finding no effect on anxiety.
Physical
Heavy, long-term exposure to marijuana may have physical, mental,
behavioral and social health consequences. It may be "associated with
diseases of the liver (particularly with co-existing hepatitis C), lungs, heart, and vasculature". A 2014 review found that while cannabis use may be less harmful than alcohol use, the recommendation to substitute it for problematic drinking was premature without further study. Various surveys conducted between 2015 and 2019 found that many users of cannabis substitute it for prescription drugs
(including opioids), alcohol, and tobacco; most of those who used it in
place of alcohol or tobacco either reduced or stopped their intake of
the latter substances.
Cannabinoid hyperemesis syndrome
(CHS) is a severe condition seen in some chronic cannabis users where
they have repeated bouts of uncontrollable vomiting for 24–48 hours.
Four cases of death have been reported as a result of CHS.
A limited number of studies have examined the effects of cannabis smoking on the respiratory system. Chronic heavy marijuana smoking is associated with respiratory infections, coughing, production of sputum, wheezing, and other symptoms of chronic bronchitis. The available evidence does not support a causal relationship between cannabis use and chronic obstructive pulmonary disease. Short-term use of cannabis is associated with bronchodilation. Other side effects of cannabis use include cannabinoid hyperemesis syndrome (CHS), a condition which involves recurrent nausea, cramping abdominal pain, and vomiting.
Cannabis smoke contains thousands of organic and inorganic chemical compounds. This tar is chemically similar to that found in tobacco smoke, and over fifty known carcinogens have been identified in cannabis smoke, including; nitrosamines, reactive aldehydes, and polycyclic aromatic hydrocarbons, including benz[a]pyrene. Cannabis smoke is also inhaled more deeply than tobacco smoke. As of 2015, there is no consensus regarding whether cannabis smoking is associated with an increased risk of cancer.
Light and moderate use of cannabis is not believed to increase risk of
lung or upper airway cancer. Evidence for causing these cancers is mixed
concerning heavy, long-term use. In general there are far lower risks
of pulmonary complications for regular cannabis smokers when compared
with those of tobacco. A 2015 review found an association between cannabis use and the development of testicular germ cell tumors (TGCTs), particularly non-seminoma TGCTs. Another 2015 meta-analysis found no association between lifetime cannabis use and risk of head or neck cancer. Combustion products are not present when using a vaporizer, consuming THC in pill form, or consuming cannabis foods.
There is concern that cannabis may contribute to cardiovascular disease, but as of 2018, evidence of this relationship was unclear.
Research in these events is complicated because cannabis is often used
in conjunction with tobacco, and drugs such as alcohol and cocaine that
are known to have cardiovascular risk factors. Smoking cannabis has also been shown to increase the risk of myocardial infarction by 4.8 times for the 60 minutes after consumption.
There is preliminary evidence that cannabis interferes with the anticoagulant properties of prescription drugs used for treating blood clots. As of 2019, the mechanisms for the anti-inflammatory and possible pain relieving
effects of cannabis were not defined, and there were no governmental
regulatory approvals or clinical practices for use of cannabis as a
drug.
Emergency department visits
Emergency room (ER) admissions associated with cannabis use rose
significantly from 2012 to 2016; adolescents from age 12–17 had the
highest risk.
At one Colorado medical center following legalization, approximately
two percent of ER admissions were classified as cannabis users. The
symptoms of one quarter of these users were partially attributed to
cannabis (a total of 2567 out of 449,031 patients); other drugs were
sometimes involved. Of these cannabis admissions, one quarter were for acute psychiatric effects, primarily suicidal ideation, depression, and anxiety. An additional third of the cases were for gastrointestinal issues including cannabinoid hyperemesis syndrome.
According to the United States Department of Health and Human
Services, there were 455,000 emergency room visits associated with
cannabis use in 2011. These statistics include visits in which the
patient was treated for a condition induced by or related to recent
cannabis use. The drug use must be "implicated" in the emergency
department visit, but does not need to be the direct cause of the visit.
Most of the illicit drug emergency room visits involved multiple drugs. In 129,000 cases, cannabis was the only implicated drug.
Reproductive health
Cannabis consumption in pregnancy is an important public health issue.
Research has found possible or likely associations between cannabis use
and a risk of adverse outcomes in respect of cognitive development,
mental health, physical health, and lactation.
THC is a weak partial agonist at CB1 receptors, while CBD is a CB1 receptor antagonist.
The CB1 receptor is found primarily in the brain as well as in some peripheral tissues, and the CB2 receptor is found primarily in peripheral tissues, but is also expressed in neuroglial cells. THC appears to alter mood and cognition through its agonist actions on the CB1 receptors, which inhibit a secondary messenger system (adenylate cyclase) in a dose-dependent manner.
The high lipid-solubility of cannabinoids results in their persisting in the body for long periods of time.
Even after a single administration of THC, detectable levels of THC can
be found in the body for weeks or longer (depending on the amount
administered and the sensitivity of the assessment method).
Investigators have suggested that this is an important factor in
marijuana's effects, perhaps because cannabinoids may accumulate in the
body, particularly in the lipid membranes of neurons.
The main psychoactive component of cannabis is tetrahydrocannabinol (THC), which is formed via decarboxylation of tetrahydrocannabinolic acid (THCA) from the application of heat. Raw leaf is not psychoactive because the cannabinoids are in the form of carboxylic acids. THC is one of the 483 known compounds in the plant, including at least 65 other cannabinoids, such as cannabidiol (CBD).
THC and its major (inactive) metabolite, THC-COOH, can be measured in blood, urine, hair, oral fluid or sweat using chromatographic techniques as part of a drug use testing program or a forensic investigation of a traffic or other criminal offense.
The concentrations obtained from such analyses can often be helpful in
distinguishing active use from passive exposure, elapsed time since use,
and extent or duration of use. These tests cannot, however, distinguish
authorized cannabis smoking for medical purposes from unauthorized
recreational smoking. Commercial cannabinoid immunoassays,
often employed as the initial screening method when testing
physiological specimens for marijuana presence, have different degrees
of cross-reactivity with THC and its metabolites. Urine contains predominantly THC-COOH, while hair, oral fluid and sweat contain primarily THC. Blood may contain both substances, with the relative amounts dependent on the recency and extent of usage.
The Duquenois–Levine test is commonly used as a screening test
in the field, but it cannot definitively confirm the presence of
cannabis, as a large range of substances have been shown to give false
positives.
Researchers at John Jay College of Criminal Justice reported that
dietary zinc supplements can mask the presence of THC and other drugs in
urine. However, a 2013 study conducted by researchers at the University of Utah School of Medicine refute the possibility of self-administered zinc producing false-negative urine drug tests.
Varieties and strains
Types of cannabisA macro cannabis bud
CBD is a 5-HT1A receptor agonist, which is under laboratory research to determine if it has an anxiolytic effect.
It is often claimed that sativa strains provide a more stimulating
psychoactive high while indica strains are more sedating with a body
high. However, this is disputed by researchers.
A 2015 review found that the use of high CBD-to-THC strains of cannabis showed significantly fewer positive symptoms, such as delusions and hallucinations, better cognitive function
and both lower risk for developing psychosis, as well as a later age of
onset of the illness, compared to cannabis with low CBD-to-THC ratios.
Psychoactive ingredients
According to the United Nations Office on Drugs and Crime (UNODC), "the amount of THC present in a cannabis sample is generally used as a measure of cannabis potency."
The three main forms of cannabis products are the flower/fruit, resin
(hashish), and oil (hash oil). The UNODC states that cannabis often
contains 5% THC content, resin "can contain up to 20% THC content", and
that "Cannabis oil may contain more than 60% THC content."
Studies have found that the potency of illicit cannabis has
greatly increased since the 1970s, with THC levels rising and CBD levels
dropping.
It is unclear, however, whether the increase in THC content has caused
people to consume more THC or if users adjust based on the potency of
the cannabis. It is likely that the higher THC content allows people to
ingest less tar. At the same time, CBD levels in seized samples have
lowered, in part because of the desire to produce higher THC levels and
because more illegal growers cultivate indoors using artificial lights.
This helps avoid detection but reduces the CBD production of the plant.
Australia's National Cannabis Prevention and Information Centre (NCPIC) states that the buds (infructescences)
of the female cannabis plant contain the highest concentration of THC,
followed by the leaves. The stalks and seeds have "much lower THC
levels". The UN states that the leaves can contain ten times less THC than the buds, and the stalks 100 times less THC.
After revisions to cannabis scheduling in the UK, the government moved cannabis back from a class C to a class B drug. A purported reason was the appearance of high potency cannabis. They believe skunk accounts for between 70% and 80% of samples seized by police (despite the fact that skunk can sometimes be incorrectly mistaken for all types of herbal cannabis). Extracts such as hashish and hash oil typically contain more THC than high potency cannabis infructescences.
Hemp buds (or low-potency cannabis buds) laced with synthetic cannabinoids started to be sold as cannabis street drug in 2020.
The short-term effects of cannabis can be altered if it has been laced with opioid drugs such as heroin or fentanyl.
The added drugs are meant to enhance the psychoactive properties, add
to its weight, and increase profitability, despite the increased danger
of overdose.
Marijuana or marihuana (herbal cannabis) consists of the dried flowers and fruits and subtending leaves and stems of the female cannabis plant. This is the most widely consumed form, containing 3% to 20% THC, with reports of up to 33% THC. This is the stock material from which all other preparations are derived. Although herbal cannabis and industrial hemp
derive from the same species and contain the psychoactive component
(THC), they are distinct strains with unique biochemical compositions
and uses. Hemp has lower concentrations of THC and higher concentrations
of CBD, which gives lesser psychoactive effects.
Hashish (also spelled hasheesh, hashisha, or simply hash) is a concentrated resin
cake or ball produced from pressed kief, the detached trichomes and
fine material that falls off cannabis fruits, flowers and leaves,
or from scraping the resin from the surface of the plants and rolling
it into balls. It varies in color from black to golden brown depending
upon purity and variety of cultivar it was obtained from. It can be consumed orally or smoked, and is also vaporized, or 'vaped'. The term "rosin hash" refers to a high quality solventless product obtained through heat and pressure.
Cannabinoids can be extracted from cannabis plant matter using high-proofspirits (often grain alcohol) to create a tincture, often referred to as "green dragon".Nabiximols is a branded product name from a tincture manufacturing pharmaceutical company.
Hash oil is a resinous matrix of cannabinoids obtained from the cannabis plant by solvent extraction, formed into a hardened or viscous mass.
Hash oil can be the most potent of the main cannabis products because
of its high level of psychoactive compound per its volume, which can
vary depending on the plant's mix of essential oils and psychoactive
compounds. Butane and supercriticalcarbon dioxide hash oil have become popular in recent years.
Infusions
There are many varieties of cannabis infusions owing to the variety of non-volatile solvents used.
The plant material is mixed with the solvent and then pressed and
filtered to express the oils of the plant into the solvent. Examples of
solvents used in this process are cocoa butter, dairy butter, cooking
oil, glycerine, and skin moisturizers. Depending on the solvent, these may be used in cannabis foods or applied topically.
Marihuana prensada ('pressed marijuana') is a cannabis-derived product widespread among the lower classes of South America, especially from the 90s. Locally it is known as "paraguayo" or "paragua", since its main producer is Paraguay. Marijuana is dried and mixed with binding agents that make it toxic and highly harmful to health. It is cut into the shape of bricks (ladrillos) and sold for a low price in Argentina, Brazil, Chile, Peru, Venezuela, and even the United States.
Present-day map of the Jirzankal Cemetery, site of the earliest evidence of cannabis smoking
Cannabis is indigenous to Central or South Asia and its uses for fabric and rope dates back to the Neolithic age in China and Japan. It is unclear when cannabis first became known for its psychoactive
properties. The oldest archeological evidence for the burning of
cannabis was found in Romanian kurgans dated 3,500 BC, and scholars suggest that the drug was first used in ritual ceremonies by Proto-Indo-European tribes living in the Pontic-Caspian steppe during the Chalcolithic period, a custom they eventually spread throughout Western Eurasia during the Indo-European migrations. Some research suggests that the ancient Indo-Iranian drug soma, mentioned in the Vedas, sometimes contained cannabis. This is based on the discovery of a basin containing cannabis in a shrine of the second millennium BC in Turkmenistan.
Cannabis was known to the ancient Assyrians, who discovered its psychoactive properties through the Iranians. Using it in some religious ceremonies, they called it qunubu (meaning "way to produce smoke"), a probable origin of the modern word cannabis. The Iranians also introduced cannabis to the Scythians, Thracians and Dacians, whose shamans (the kapnobatai – "those who walk on smoke/clouds") burned cannabis infructescences to induce trance. The plant was used in China before 2800 BC, and found therapeutic use in India by 1000 BC, where it was used in food and drink, including bhang.
Cannabis has an ancient history of ritual use and has been used by
religions around the world. It has been used as a drug for both recreational and entheogenic purposes and in various traditional medicines for centuries. The earliest evidence of cannabis smoking has been found in the 2,500-year-old tombs of Jirzankal Cemetery in the Pamir Mountains in Western China, where cannabis residue were found in burners with charred pebbles possibly used during funeral rituals. Hemp seeds discovered by archaeologists at Pazyryk
suggest early ceremonial practices like eating by the Scythians
occurred during the 5th to 2nd century BC, confirming previous
historical reports by Herodotus. It was used by Muslims in various Sufi orders as early as the Mamluk period, for example by the Qalandars. Smoking pipes uncovered in Ethiopia and carbon-dated to around c. AD 1320 were found to have traces of cannabis.
Modern history
Cannabis was introduced to the New World by the Spaniards in 1530–1545. Following an 1836–1840 travel in North Africa and the Middle East, French physician Jacques-Joseph Moreau wrote on the psychological effects of cannabis use; he founded the Paris' Club des Hashischins in 1844. In 1842, Irish physician William Brooke O'Shaughnessy, who had studied the drug while working as a medical officer in Bengal with the East India Company, brought a quantity of cannabis with him on his return to Britain, provoking renewed interest in the West. Examples of classic literature of the period featuring cannabis include Les paradis artificiels (1860) by Charles Baudelaire and The Hasheesh Eater (1857) by Fitz Hugh Ludlow.
Anti-cannabis propaganda from 1935
Cannabis was criminalized in some countries beginning in the 14th
century and was illegal in most countries by the middle of the 20th
century. The colonial government of Mauritius banned cannabis in 1840
over concerns on its effect on Indian indentured workers; the same occurred in Singapore in 1870. In the United States, the first restrictions on sale of cannabis came in 1906 (in the District of Columbia). Canada criminalized cannabis in The Opium and Narcotic Drug Act, 1923,
before any reports of the use of the drug in Canada, but eventually
legalized its consumption for recreational and medicinal purposes in
2018.
In 1925, a compromise was made at an international conference in The Hague about the International Opium Convention
that banned exportation of "Indian hemp" to countries that had
prohibited its use, and requiring importing countries to issue
certificates approving the importation and stating that the shipment was
required "exclusively for medical or scientific purposes". It also
required parties to "exercise an effective control of such a nature as
to prevent the illicit international traffic in Indian hemp and
especially in the resin". In the United States in 1937, the Marihuana Tax Act was passed, and prohibited the production of hemp in addition to cannabis.
Cannabis indica fluid extract, American Druggists Syndicate (pre-1937)
In 1972, the Dutch government divided drugs into more- and
less-dangerous categories, with cannabis being in the lesser category.
Accordingly, possession of 30 grams (1.1 oz) or less was made a
misdemeanor. Cannabis has been available for recreational use in coffee shops since 1976.
Cannabis products are only sold openly in certain local "coffeeshops"
and possession of up to 5 grams (0.18 oz) for personal use is
decriminalized, however: the police may still confiscate it, which often
happens in car checks near the border. Other types of sales and
transportation are not permitted, although the general approach toward
cannabis was lenient even before official decriminalization.
In Uruguay, President Jose Mujica signed legislation to legalize recreational cannabis
in December 2013, making Uruguay the first country in the modern era to
legalize cannabis. In August 2014, Uruguay legalized growing up to six
plants at home, as well as the formation of growing clubs (Cannabis social club), and a state-controlled marijuana dispensary regime.
As of 17 October 2018, when recreational use of cannabis was legalized in Canada, dietary supplements for human use and veterinary health products containing not more than 10 parts per million of THC extract were approved for marketing; Nabiximols (as Sativex) is used as a prescription drug in Canada.
The United Nations' World Drug Report
stated that cannabis "was the world's most widely produced, trafficked,
and consumed drug in the world in 2010", and estimated between 128
million and 238 million users globally in 2015.
Process of making bhang in a village in Punjab, India. On the Indian festival of colors, Holi, it is a customary addition to some intoxicating drinks.
Cannabis has been one of the most used psychoactive drugs in the world since the late 20th century, following only tobacco and alcohol in popularity.
According to Vera Rubin, the use of cannabis has been encompassed by
two major cultural complexes over time: a continuous, traditional folk stream, and a more circumscribed, contemporary configuration. The former involves both sacred and secular use, and is usually based on small-scale cultivation: the use of the plant for cordage, clothing, medicine, food, and a "general use as an euphoriant and symbol of fellowship."
The second stream of expansion of cannabis use encompasses "the use of
hemp for commercial manufacturers utilizing large-scale cultivation
primarily as a fiber for mercantile purposes"; but it is also linked to
the search for psychedelic experiences (which can be traced back to the formation of the Parisian Club des Hashischins).
Since the beginning of the 20th century, most countries have enacted laws against the cultivation, possession or transfer of cannabis.
These laws have had an adverse effect on cannabis cultivation for
non-recreational purposes, but there are many regions where handling of
cannabis is legal or licensed. Many jurisdictions have lessened the
penalties for possession of small quantities of cannabis so that it is
punished by confiscation and sometimes a fine, rather than imprisonment,
focusing more on those who traffic the drug on the black market.
In some areas where cannabis use had been historically tolerated,
new restrictions were instituted, such as the closing of cannabis
coffee shops near the borders of the Netherlands, and closing of coffee shops near secondary schools in the Netherlands. In Copenhagen, Denmark in 2014, mayor Frank Jensen discussed possibilities for the city to legalize cannabis production and commerce.
Some jurisdictions use free voluntary or mandatory treatment
programs for frequent known users. Simple possession can carry long
prison terms in some countries, particularly in East Asia, where the
sale of cannabis may lead to a sentence of life in prison or even
execution. Political parties, non-profit organizations, and causes based
on the legalization of medical cannabis or legalizing the plant
entirely (with some restrictions) have emerged in such countries as
China and Thailand.
In December 2012, the U.S. state of Washington became the first state to officially legalize cannabis in a state law (Washington Initiative 502) (but still illegal by federal law), with the state of Colorado following close behind (Colorado Amendment 64). On 1 January 2013, the first cannabis "club" for private marijuana smoking (no buying or selling, however) was allowed for the first time in Colorado.
The California Supreme Court decided in May 2013 that local governments
can ban medical cannabis dispensaries despite a state law in California
that permits the use of cannabis for medical purposes. At least 180
cities across California have enacted bans in recent years.
In December 2013, Uruguay became the first country to legalize growing, sale and use of cannabis.
After a long delay in implementing the retail component of the law, in
2017 sixteen pharmacies were authorized to sell cannabis commercially.
On 19 June 2018, the Canadian Senate passed a bill and the Prime
Minister announced the effective legalization date as 17 October 2018. Canada is the second country to legalize the drug.
In November 2015, Uttarakhand became the first state of India to legalize the cultivation of hemp for industrial purposes. Usage within the Hindu and Buddhist cultures of the Indian subcontinent
is common, with many street vendors in India openly selling products
infused with cannabis, and traditional medical practitioners in Sri
Lanka selling products infused with cannabis for recreational purposes
and well as for religious celebrations. Indian laws criminalizing cannabis date back to the colonial period.
India and Sri Lanka have allowed cannabis to be taken in the context of
traditional culture for recreational/celebratory purposes and also for
medicinal purposes.
On 17 October 2015, Australian health minister Sussan Ley presented a new law that will allow the cultivation of cannabis for scientific research and medical trials on patients.
On 17 October 2018, Canada legalized cannabis for recreational adult use making it the second country in the world to do so after Uruguay and the first G7 nation. This legalization comes with regulation similar to that of alcohol in Canada, age restrictions, limiting home production, distribution, consumption areas and sale times. Laws around use vary from province to province including age limits, retail structure, and growing at home. The Canadian Licensed Producer system aims to become the Gold Standard in the world for safe and secure cannabis production,
including provisions for a robust craft cannabis industry where many
expect opportunities for experimenting with different strains.
As the drug has increasingly been seen as a health issue instead of criminal behavior, cannabis has also been legalized or decriminalized in: Czech Republic, Colombia, Ecuador, Portugal, South Africa and Canada. Medical marijuana was legalized in Mexico in mid-2017 and legalized for recreational use in June 2021.
Germany legalized cannabis for recreational use in April 2024.
Legal status by country
As of 2022, Uruguay and Canada
are the only countries that have fully legalized the cultivation,
consumption and bartering of recreational cannabis nationwide. In the United States,
24 states, 3 territories, and the District of Columbia have legalized
the recreational use of cannabis – though the drug remains illegal at
the federal level. Laws vary from state to state when it comes to the commercial sale. Court rulings in Georgia
and South Africa have led to the legalization of cannabis consumption,
but not legal sales. A policy of limited enforcement has also been
adopted in many countries, in particular Spain and the Netherlands where the sale of cannabis is tolerated at licensed establishments.Contrary to popular belief, cannabis is not legal in the Netherlands, but it has been decriminalized since the 1970s. In 2021, Malta was the first European Union member to legalize the use of cannabis for recreational purposes. In Estonia,
it is only legal to sell cannabis products with a THC content of less
than 0.2%, although products may contain more cannabidiol. Lebanon has recently become the first Arab country to legalize the plantation of cannabis for medical use.
Penalties for illegal recreational use ranges from confiscation or small fines to jail time and even death. In some countries citizens can be punished if they have used the drug in another country, including Singapore and South Korea.
Woman selling cannabis and bhang in Guwahati, Assam, India
Sinsemilla (Spanish for "without seed") is the dried, seedless (i.e. parthenocarpic) infructescences of female cannabis plants.
Because THC production drops off once pollination occurs, the male
plants (which produce little THC themselves) are eliminated before they
shed pollen to prevent pollination, thus inducing the development of parthenocarpic fruits gathered in dense infructescences. Advanced cultivation techniques such as hydroponics, cloning, high-intensity artificial lighting, and the sea of green method are frequently employed as a response (in part) to prohibition enforcement efforts that make outdoor cultivation more risky.
"Skunk" refers to several named strains of potent cannabis, grown through selective breeding and sometimes hydroponics. It is a cross-breed of Cannabis sativa and C. indica
(although other strains of this mix exist in abundance). Skunk cannabis
potency ranges usually from 6% to 15% and rarely as high as 20%. The
average THC level in coffee shops in the Netherlands is about 18–19%.
The average levels of THC in cannabis sold in the United States rose dramatically between the 1970s and 2000.
This is disputed for various reasons, and there is little consensus as
to whether this is a fact or an artifact of poor testing methodologies.
According to Daniel Forbes writing for slate.com, the relative strength
of modern strains are likely skewed because undue weight is given to
much more expensive and potent, but less prevalent, samples.
Some suggest that results are skewed by older testing methods that
included low-THC-content plant material such as leaves in the samples,
which are excluded in contemporary tests. Others believe that modern
strains actually are significantly more potent than older ones.
The main producing countries of cannabis are Afghanistan, Canada, China, Colombia, India, Jamaica, Lebanon, Mexico, Morocco, the Netherlands, Pakistan, Paraguay, Spain, Thailand, Turkey, the United Kingdom, and the United States.
Price
The price or street value of cannabis varies widely depending on geographic area and potency. Prices and overall markets have also varied considerably over time.
In 1997, cannabis was estimated to be overall the number four
value crop in the US, and number one or two in many states, including
California, New York, and Florida. This estimate is based on a value to
growers of ~60% of retail value, or $3,000 per pound ($6,600/kg).
In 2006, cannabis was estimated to have been a $36 billion market. This estimate has been challenged as exaggerated.
The UN World Drug Report (2008) estimated that 2006 street prices in
the US and Canada ranged from about US$8.8 to $25 per gram
(approximately $250 to $700 per ounce), depending on quality. Typical U.S. retail prices were $10–15 per gram (approximately $280–420 per ounce).
In 2017, the U.S. was estimated to constitute 90% of the worldwide $9.5 billion legal trade in cannabis.
After some U.S. states legalized cannabis, street prices began to
drop. In Colorado, the price of smokable buds (infructescences) dropped
40 percent between 2014 and 2019, from $200 per ounce to $120 per ounce
($7 per gram to $4.19 per gram).
The European Monitoring Centre for Drugs and Drug Addiction
reports that typical retail prices in Europe for cannabis varied from
€2 to €20 per gram in 2008, with a majority of European countries
reporting prices in the range €4–10.
The gateway hypothesis states that cannabis use increases the
probability of trying "harder" drugs. The hypothesis has been hotly
debated as it is regarded by some as the primary rationale for the
United States prohibition on cannabis use. A Pew Research Center
poll found that political opposition to marijuana use was significantly
associated with concerns about the health effects and whether
legalization would increase cannabis use by children.
Some studies state that while there is no proof for the gateway hypothesis, young cannabis users should still be considered as a risk group for intervention programs. Other findings indicate that hard drug users are likely to be poly-drug users, and that interventions must address the use of multiple drugs instead of a single hard drug. Almost two-thirds of the poly drug users in the 2009–2010 Scottish Crime and Justice Survey used cannabis.
The gateway effect may appear due to social factors involved in
using any illegal drug. Because of the illegal status of cannabis, its
consumers are likely to find themselves in situations allowing them to
acquaint with individuals using or selling other illegal drugs. Studies have shown that alcohol and tobacco may additionally be regarded as gateway drugs;
however, a more parsimonious explanation could be that cannabis is
simply more readily available (and at an earlier age) than illegal hard
drugs.
In turn, alcohol and tobacco are typically easier to obtain at an
earlier age than is cannabis (though the reverse may be true in some
areas), thus leading to the "gateway sequence" in those individuals,
since they are most likely to experiment with any drug offered.
A related alternative to the gateway hypothesis is the common
liability to addiction (CLA) theory. It states that some individuals
are, for various reasons, willing to try multiple recreational
substances. The "gateway" drugs are merely those that are (usually)
available at an earlier age than the harder drugs. Researchers have
noted in an extensive review that it is dangerous to present the
sequence of events described in gateway "theory" in causative terms as
this hinders both research and intervention.
In 2020, the National Institute on Drug Abuse
released a study backing allegations that marijuana is a gateway to
harder drugs, though not for the majority of marijuana users.
The National Institute on Drug Abuse determined that marijuana use is
"likely to precede use of other licit and illicit substances" and that
"adults who reported marijuana use during the first wave of the survey
were more likely than adults who did not use marijuana to develop an
alcohol use disorder within 3 years; people who used marijuana and
already had an alcohol use disorder at the outset were at greater risk
of their alcohol use disorder worsening. Marijuana use is also linked to
other substance use disorders including nicotine addiction."
It also reported that "These findings are consistent with the idea of
marijuana as a "gateway drug". However, the majority of people who use
marijuana do not go on to use other, "harder" substances. Also,
cross-sensitization is not unique to marijuana. Alcohol and nicotine
also prime the brain for a heightened response to other drugs and are,
like marijuana, also typically used before a person progresses to other,
more harmful substances."
Research on cannabis is challenging since the plant is illegal in most countries.
Research-grade samples of the drug are difficult to obtain for research
purposes, unless granted under authority of national regulatory
agencies, such as the US Food and Drug Administration.
There are also other difficulties in researching the effects of cannabis. Many people who smoke cannabis also smoke tobacco.
This causes confounding factors, where questions arise as to whether
the tobacco, the cannabis, or both that have caused a cancer. Another
difficulty researchers have is in recruiting people who smoke cannabis
into studies. Because cannabis is an illegal drug in many countries,
people may be reluctant to take part in research, and if they do agree
to take part, they may not say how much cannabis they actually smoke.
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