Pesticide residue refers to the pesticides that may remain on or in food after they are applied to food crops.
The maximum allowable levels of these residues in foods are often
stipulated by regulatory bodies in many countries. Regulations such as
pre-harvest intervals also often prevent harvest of crop or livestock
products if recently treated in order to allow residue concentrations to
decrease over time to safe levels before harvest. Exposure of the
general population to these residues most commonly occurs through
consumption of treated food sources, or being in close contact to areas
treated with pesticides such as farms or lawns.
Many of these chemical residues, especially derivatives of chlorinated pesticides, exhibit bioaccumulation which could build up to harmful levels in the body as well as in the environment. Persistent chemicals can be magnified through the food chain and have been detected in products ranging from meat, poultry, and fish, to vegetable oils, nuts, and various fruits and vegetables.
Many of these chemical residues, especially derivatives of chlorinated pesticides, exhibit bioaccumulation which could build up to harmful levels in the body as well as in the environment. Persistent chemicals can be magnified through the food chain and have been detected in products ranging from meat, poultry, and fish, to vegetable oils, nuts, and various fruits and vegetables.
Definition
A pesticide is a substance or a mixture of substances used for killing pests: organisms dangerous to cultivated plants or to animals. The term applies to various pesticides such as insecticide, fungicide, herbicide and nematocide.
Applications of pesticides to crops and animals may leave residues in
or on food when it is consumed, and those specified derivatives are
considered to be of toxicological significance.
Background
From post-World War II era, chemical pesticides have become the most important form of pest control.
There are two categories of pesticides, first-generation pesticides and
second-generation pesticide. The first-generation pesticides, which
were used prior to 1940, consisted of compounds such as arsenic, mercury, and lead.
These were soon abandoned because they were highly toxic and
ineffective. The second-generation pesticides were composed of synthetic
organic compounds. The growth in these pesticides accelerated in late
1940s after Paul Müller discovered DDT in 1939. The effects of pesticides such as aldrin, dieldrin, endrin, chlordane, parathion, captan and 2,4-D were also found at this time.
Those pesticides were widely used due to its effective pest control.
However, in 1946, people started to resist to the widespread use of
pesticides, especially DDT since it harms non-target plants and animals. People became aware of problems with residues and its potential health risks. In the 1960s, Rachel Carson wrote Silent Spring to illustrate a risk of DDT and how it is threatening biodiversity.
Regulations
Each country adopts their own agricultural policies and Maximum Residue Limits (MRL) and Acceptable Daily Intake
(ADI). The level of food additive usage varies by country because forms
of agriculture are different in regions according to their geographical
or climatical factors.
Pre-harvest intervals are also set to require a crop or livestock
product not be harvested before a certain period after application in
order to allow the pesticide residue to decrease below maximum residue
limits or other tolerance levels.
Likewise, restricted entry intervals are the amount of time to allow
residue concentrations to decrease before a worker can reenter an area
where pesticides have been applied without protective equipment.
International
Some countries use the International Maximum Residue Limits -Codex Alimentarius to define the residue limits; this was established by Food and Agriculture Organization of the United Nations (FAO) and World Health Organization
(WHO) in 1963 to develop international food standards, guidelines
codes of practices, and recommendation for food safety. Currently the
CODEX has 185 Member Countries and 1 member organization (EU).
The following is the list of maximum residue limits (MRLs) for spices adopted by the commission.
| Pesticide | Group or sub-group of spices | MRL (mg/kg) |
|---|---|---|
| Acephate | Entire Group 028 | 0.2 |
| Azinphos-methyl | Entire Group 028 | 0.5 |
| Chlorpyrifos | Seeds Fruits or berries Roots or rhizomes |
5 1 1 |
| Chlorpyrifos-methyl | Seeds Fruits or berries Roots or rhizomes |
1 0.3 5 |
| Cypermethrin | Fruits or berries Roots or rhizomes |
0.1 0.2 |
| Diazinon | Seeds Fruits Roots or rhizomes |
5 0.1 0.5 |
| Dichlorvos | Entire Group 028 | 0.1 |
| Dicofol | Seeds Fruits or berries Roots or rhizomes |
0.05 0.1 0.1 |
| Dimethoate | Seeds Fruits or berries Roots or rhizomes |
5 0.5 0.1 |
| Disulfoton | Entire Group 028 | 0.05 |
| Endosulfan | Seeds Fruits or berries Roots or rhizomes |
1 5 0.5 |
| Ethion | Seeds Fruits or berries Roots or rhizomes |
3 5 0.3 |
| Fenitrothion | Seeds Fruits or berries Roots or rhizomes |
7 1 0.1 |
| Iprodione | Seeds Fruits or berries Roots or rhizomes |
7 1 0.1 |
| Malathion | Seeds Fruits or berries Roots or rhizomes |
2 1 0.5 |
| Metalaxyl | Seeds | 5 |
| Methamidophos | Entire Group 028 | 0.1 |
| Parathion | Seeds Fruits or berries Roots or rhizomes |
0.1 0.2 0.2 |
| Parathion-methyl | Seeds Fruits or berries Roots or rhizomes |
5 5 0.3 |
| Permethrin | Entire Group 028 | 0.05 |
| Phenthoate | Seeds | 7 |
| Phorate | Seeds Fruits or berries Roots or rhizomes |
0.5 0.1 0.1 |
| Phosalone | Seeds Fruits or berries Roots or rhizomes |
2 2 3 |
| Pirimicarb | Seeds | 5 |
| Pirimiphos-methyl | Seeds sub group Fruits sub group |
3 0.5 |
| Quintozene | Seeds sub group Fruits or berries Roots or rhizomes |
0.1 0.02 2 |
| Vinclozolin | Entire spice group | 0.05 |
European Union
In September 2008, the European Union issued new and revised Maximum
Residue Limits (MRLs) for the roughly 1,100 pesticides ever used in the
world. The revision was intended to simplify the previous system, under
which certain pesticide residues were regulated by the Commission;
others were regulated by Member States, and others were not regulated at
all.
New Zealand
Food Standards Australia New Zealand develops the standards for levels of pesticide residues in foods through a consultation process. The New Zealand Food Safety Authority publishes the maximum limits of pesticide residues for foods produced in New Zealand.
United Kingdom
Monitoring
of pesticide residues in the UK began in the 1950s. From 1977 to 2000
the work was carried out by the Working Party on Pesticide Residues
(WPPR), until in 2000 the work was taken over by the Pesticide Residue
Committee (PRC). The PRC advise the government through the Pesticides
Safety Directorate and the Food Standards Agency (FSA).
United States
In the US, tolerances for the amount of pesticide residue that may remain on food are set by the EPA,
and measures are taken to keep pesticide residues below the tolerances.
The US EPA has a web page for the allowable tolerances.
In order to assess the risks associated with pesticides on human
health, the EPA analyzed individual pesticide active ingredients as well
as the common toxic effect that groups of pesticides have, called the
cumulative risk assessment. Limits that the EPA sets on pesticides
before approving them includes a determination of how often the
pesticide should be used and how it should be used, in order to protect
the public and the environment. In the US, the Food and Drug Administration (FDA) and USDA also routinely check food for the actual levels of pesticide residues.
A US organic food advocacy group, the Environmental Working Group,
is known for creating a list of fruits and vegetables referred to as
the Dirty Dozen; it lists produce with the highest number of distinct
pesticide residues or most samples with residue detected in USDA
data. This list is generally considered misleading and lacks scientific
credibility because it lists detections without accounting for the risk
of the usually small amount of each residue with respect to consumer
health. In 2016, over 99% of samples of US produce had no pesticide residue or had residue levels well below the EPA tolerance levels for each pesticide.
Japan
In Japan, pesticide residues are regulated by the Food Safety Act.
Pesticide tolerances are set by the Ministry of Health, Labour and Welfare through the Drug and Food Safety Committee. Unlisted residue amounts are restricted to 0.01ppm.
China
In China, the Ministry of Health and the Ministry of Agriculture
have jointly established mechanisms and working procedures relating to
maximum residue limit standards, while updating them continuously,
according to the food safety law and regulations issued by the State Council. From GB25193-2010 to GB28260-2011,
from Maximum Residue Limits for 12 Pesticides to 85 pesticides, they
have improved the standards in response to Chinese national needs.
Health impacts
Many pesticides achieve their intended use of killing pests by disrupting the nervous system.
Due to similarities in brain biochemistry among many different
organisms, there is much speculation that these chemicals can have a
negative impact on humans as well.
There are epidemiological
studies that show positive correlations between exposure to pesticides
through occupational hazard, which tends to be significantly higher than
that ingested by the general population through food, and the
occurrence of certain cancers.
Although most of the general population may not exposed to large
portion of pesticides, many of the pesticide residues that are attached
tend to be lipophilic and can bio-accumulate in the body.
According to the American Cancer Society there is no evidence that pesticide residues increase the risk of people getting cancer. Pesticide exposure cannot be studied in placebo controlled trials as this would be unethical. A definitive cause effect relationship therefore cannot be established. The ACA advises washing fruit and vegetables before eating to remove both pesticide residue and other undesirable contaminants.
Chinese incidents
In
China, a number of incidents have occurred where state limits were
exceeded by large amounts or where the wrong pesticide was used. In
August 1994, a serious incident of pesticide poisoning of sweet potato
crops occurred in Shandong province, China. Because local farmers were
not fully educated in the use of insecticides, they used the
highly-toxic pesticide named parathion instead of trichlorphon.
It resulted in over 300 cases of poisoning and 3 deaths. Also, there
was a case where a large number of students were poisoned and 23 of them
were hospitalized because of vegetables that contained excessive
pesticide residues.
Child neurodevelopment
Children are thought to be especially vulnerable to exposure to
pesticide residues, especially if exposure occurs at critical windows of
development. Infants and children consume higher amounts of food and
water relative to their body-weight have higher surface area (i.e. skin
surface) relative to their volume, and have a more permeable blood-brain barrier,
and engage in behaviors like crawling and putting objects in their
mouths, all of which can contribute to increased risks from exposure to
pesticide residues through food or environmental routes. Neurotoxins and other chemicals that originate from pesticides pose the biggest threat to the developing human brain and nervous system. Presence of pesticide metabolites in urine samples have been implicated in disorders such as attention deficit hyperactivity disorder (ADHD), autism, behavioral and emotional problems, and delays in development. There is a lack of evidence of a direct cause-and-effect
relationship between long-term, low-dose exposure to pesticide residues
and neurological disease, partly because manufacturers are not always
legally required to examine potential long-term threats.
