Piglet and Pooh go in circles hunting a Woozle—but the tracks they follow are merely their own.
The Woozle effect, also known as evidence by citation,
occurs when a source is widely cited for a claim that the source does
not adequately support, giving said claim undeserved credibility. If
results are not replicated
and no one notices that a key claim was never well-supported in its
original publication, faulty assumptions may affect further research.
The Woozle effect is somewhat similar to circular reporting
in journalism, where someone makes a questionable claim, and a
journalist unthinkingly accepts the claim and republishes it without
realizing its dubious and unreliable origins. In turn, other journalists
and the public then continue to repeat and duplicate the unsupported
claim.
Origin and definition
A Woozle is an imaginary character in the A. A. Milne book Winnie-the-Pooh, published in 1926. In chapter three, "In which Pooh and Piglet Go Hunting and Nearly Catch a Woozle", Winnie-the-Pooh and Piglet start following tracks left in snow believing they are the tracks of an imaginary animal called a woozle. The tracks keep multiplying until Christopher Robin explains to them that they have been following their own tracks in circles around a spinney.
Prior to the introduction of the specific term "Woozle effect",
the underlying concept dates back over 60 years. Bevan (1953), writing
about scientific methodology and research errors in the field of
psychology, uses the term "scientific woozle hunters". Wohlwill (1963) refers to a "hunt for the woozle" in social science research, and Stevens (1971) cautions readers about woozles in the study of a misquoted letter.
The term "woozle effect" was coined by Beverly D. Houghton in 1979
during a panel discussion, in order: "...to critique the burgeoning
belief in a myth/archetype [of] the batterer emerging from the [then]
virtually nonexistent literature and the popular press." More recently she described the effect as "reification-by-accretion". Other researchers have attributed the term to Richard Gelles (1980), and to Gelles and Murray A. Straus (1988).
Gelles and Straus argue that the woozle effect describes a pattern of
bias seen within social sciences and which is identified as leading to
multiple errors in individual and public perception, academia, policy
making, and government.
A woozle is also a claim, made about research, that is not supported by original findings. According to Donald G. Dutton,
a woozle effect, or a woozle, occurs when frequent citation of previous
publications that lack evidence misleads individuals, groups and the
public into thinking or believing there is evidence, and non-facts
become urban myths and factoids.
The creation of woozles is often linked to the changing of language
from qualified ("it may", "it might", "it could") to absolute form ("it
is"), firming up language and introducing ideas and views not held by an
original author or supported by evidence.
Dutton sees the woozle effect as an example of confirmation bias and links it to belief perseverance and groupthink.
Because in the social sciences empirical evidence may be based on
experiential reports rather than objective measurements, there may be a
tendency for researchers to align evidence with expectation. According
to Dutton, it is also possible that the social sciences may be likely to
align with contemporary views and ideals of social justice, leading to
bias in favor of those ideals. Gambrill (2012) links the woozle effect to the processes that create pseudoscience.
Gambrill and Reiman (2011) also link it with more deliberate propaganda
techniques; they also identify introductory phrases like "Every one
knows ...", "It is clear that ...", "It is obvious that ...", "It is
generally agreed that ..." as alarm bells that what follows might be a
Woozle line of reasoning.
Examples
In 1980, Gelles illustrated the Woozle effect, showing how work by Gelles (1974) based on a small sample and published in The Violent Home by Straus, who had written the foreword for Gelles's book, was presented as if it applied to a large sample. Both of these were then cited by Langley & Levy in their 1977 book, Wife Beating: The Silent Crisis. In the 1998 book Intimate Violence,
Gelles and Straus use the Winnie-the-Pooh woozle to illustrate how poor
practice in research and self-referential research causes older
research to be taken as fresh evidence causing error and bias.
One notable example of the effect can be seen in citations of "Addiction Rare in Patients Treated with Narcotics", a letter to the editor by Jane Porter and Hershel Jick published by the New England Journal of Medicine in 1980. The letter, which was five sentences long and unlikely to have been peer reviewed according to a NEJM spokesperson,
reported findings from analysis of medical records regarding the use of
pain medication for hospital patients and concluded that "despite
widespread use of narcotic drugs in hospitals, the development of
addiction is rare in medical patients with no history of addiction".
Although the study only concerned use of narcotics in hospital
settings, over time it was increasingly cited to support claims that
addiction to painkillers was similarly uncommon among patients
prescribed narcotics to take at home.
The authors of a 2017 letter published in the NEJM concerning the
original 1980 letter found 608 citations of Porter and Jick, with a
"sizable increase" after the release of OxyContin in 1995: Purdue Pharma,
the manufacturers of OxyContin, cited the Porter and Jick study, as
well as others, to argue that it carried a low risk of addiction.
In 2007, Purdue and three of the company's senior executives pleaded
guilty to federal criminal charges that they had misled regulators,
physicians and patients about the addiction risk associated with taking
OxyContin.
The 1980 study was also misrepresented in both academic and
non-academic publications: it was described as an "extensive study" by Scientific American, whilst Time
said that it was a "landmark study" showing that "exaggerated fear that
patients would become addicted" to opiates was "basically unwarranted", and an article in the journal Seminars in Oncology
claimed that the Porter and Jick study examined cancer patients when
the letter made no mention of what illnesses the patients were suffering
from.
The authors of the 2017 NEJM letter suggested that the inappropriate
citations of the 1980 study played a role in the North American opioid epidemic by under-representing the risk of addiction:
the page for the Porter and Jick letter on the Journal's website now
includes a note informing the reader that it "has been 'heavily and
uncritically cited' as evidence that addiction is rare with opioid
therapy".
In a study conducted by the Vera Institute of Justice, Weiner and Hala (2008) reported some of the research-related difficulties associated with measuring human trafficking. They describe and map the unfolding of the Woozle effect in connection with prevalence
estimates of human trafficking. Searching the relevant literature
between 1990 and 2006, Weiner and Hala found 114 prevalence estimates in
45 publications. Only one of the publications cited original research, and several prevalence estimates appeared unsourced. The authors concluded that the sources they reviewed lacked citations, adequate operational definition, and discussion of methodology. Stransky and Finkelhor (2008/2012) criticize the general methodology involved in human trafficking research. They cite the Woozle effect
and post a prominent warning on the first page of their report
cautioning against citing any specific estimates they present, as the
close inspection of the figures "...reveals that none are based on a
strong scientific foundation."
Gambrill and Reiman (2011) analyze scientific papers and mass-market communications about social anxiety and conclude that many of them engage in disease mongering
by presenting the disease model of social anxiety as an
incontrovertible fact by resorting to unchallenged repetition techniques
and by leaving out of the discourse any competing theories. Gambrill
and Reiman further note that even after educating their subjects about
the tell-tale signs of such techniques, many of them still failed to
pick up the signs in a practical test.
Geraldine Hoff Doyle
claimed to have been the inspiration for the "We Can Do It!" poster,
achieving fame and honors when her statement – likely false – was
repeated without confirmation.
James J. Kimble gives as an example the 1994–2015 historiography of the 1943 American "We Can Do It!" wartime poster. After Michigan resident Geraldine Hoff Doyle
said in 1994 that she was the real-life model for the poster, many
sources repeated her assertion without checking the two foundational
assumptions: that Doyle was the young factory worker pictured in a 1942
wartime photograph, and that the photograph had inspired commercial
artist J. Howard Miller
to create the poster. Though some media representations described the
connection as unconfirmed, many more enthusiastically endorsed it. The
weight of these multiple endorsements gave Doyle's story a "convincing"
authority, despite the lack of authority in establishing the connection.
In 2015, Kimble found the original photographic print of the factory
worker, its caption identifying the young woman as Naomi Parker, working in California in March 1942, when Doyle was still in high school.
Treatment may involve some combination of chemotherapy, radiation therapy, targeted therapy, and bone marrow transplant, with supportive and palliative care provided as needed. Certain types of leukemia may be managed with watchful waiting.
The success of treatment depends on the type of leukemia and the age of
the person. Outcomes have improved in the developed world. Five-year survival rate was 67% in the United States in the period from 2014 to 2020. In children under 15 in first-world
countries, the five-year survival rate is greater than 60% or even 90%,
depending on the type of leukemia. For infants (those diagnosed under
the age of 1), the survival rate is around 40%. In children who are cancer-free five years after diagnosis of acute leukemia, the cancer is unlikely to return.
In 2015, leukemia was present in 2.3 million people worldwide and caused 353,500 deaths. In 2012, it had newly developed in 352,000 people.
It is the most common type of cancer in children, with three-quarters
of leukemia cases in children being the acute lymphoblastic type. However, over 90% of all leukemias are diagnosed in adults, CLL and AML being most common. It occurs more commonly in the developed world.
Clinically and pathologically, leukemia is subdivided into a variety of large groups. The first division is between its acute and chronic forms:
Acute leukemia
is characterized by a rapid increase in the number of immature blood
cells. The crowding that results from such cells makes the bone marrow
unable to produce healthy blood cells resulting in low hemoglobin and low platelets. Immediate treatment is required in acute leukemia because of the rapid progression and accumulation of the malignant cells,
which then spill over into the bloodstream and spread to other organs
of the body. Acute forms of leukemia are the most common forms of leukemia in children.
Chronic leukemia is characterized by the excessive buildup of relatively mature, but still abnormal, white blood cells (or, more rarely, red blood cells).
Typically taking months or years to progress, the cells are produced at
a much higher rate than normal, resulting in many abnormal white blood
cells. Whereas acute leukemia must be treated immediately, chronic forms
are sometimes monitored for some time before treatment to ensure
maximum effectiveness of therapy. Chronic leukemia mostly occurs in
older people but can occur in any age group.
In lymphoblastic or lymphocytic leukemias, the cancerous change takes place in a type of marrow cell that normally goes on to form lymphocytes, which are infection-fighting immune system cells. Most lymphocytic leukemias involve a specific subtype of lymphocyte, the B cell.
Combining these two classifications provides a total of four main
categories. Within each of these main categories, there are typically
several subcategories. Finally, some rarer types are usually considered
to be outside of this classification scheme.
Chronic lymphocytic leukemia
(CLL) most often affects adults over the age of 55. It sometimes occurs
in younger adults, but it almost never affects children. Two-thirds of
affected people are men. The five-year survival rate is 85%. It is incurable, but there are many effective treatments. One subtype is B-cell prolymphocytic leukemia, a more aggressive disease.
Chronic myelogenous leukemia (CML) occurs mainly in adults; a very small number of children also develop this disease. It is treated with imatinib (Gleevec in United States, Glivec in Europe) or other drugs. The five-year survival rate is 90%. One subtype is chronic myelomonocytic leukemia.
Hairy cell leukemia
(HCL) is sometimes considered a subset of chronic lymphocytic leukemia,
but does not fit neatly into this category. About 80% of affected
people are adult men. No cases in children have been reported. HCL is
incurable but easily treatable. Survival is 96% to 100% at ten years.
T-cell prolymphocytic leukemia (T-PLL) is a very rare and aggressive leukemia affecting adults; somewhat more men than women are diagnosed with this disease. Despite its overall rarity, it is the most common type of mature T cell leukemia; nearly all other leukemias involve B cells. It is difficult to treat, and the median survival is measured in months.
Adult T-cell leukemia is caused by human T-lymphotropic virus (HTLV), a virus similar to HIV.
Like HIV, HTLV infects CD4+ T-cells and replicates within them;
however, unlike HIV, it does not destroy them. Instead, HTLV
"immortalizes" the infected T-cells, giving them the ability to
proliferate abnormally. Human T-cell lymphotropic virus types I and II
(HTLV-I/II) are endemic in certain areas of the world.
Transient myeloproliferative disease, also termed transient leukemia, involves the abnormal proliferation of a clone of non-cancerous megakaryoblasts. The disease is restricted to individuals with Down syndrome
or genetic changes similar to those in Down syndrome, develops in a
baby during pregnancy or shortly after birth, and resolves within 3
months or, in ~10% of cases, progresses to acute megakaryoblastic leukemia. Transient myeloid leukemia is a pre-leukemic condition.
Clonal hematopoiesis is a common age-related phenomenon with a low risk of progression to myelodysplastic syndrome (MDS) and leukemia.
Once MDS has developed, the risk of progression to acute leukemia can
be assessed using the International Prognostic Scoring System (IPSS).
Damage to the bone marrow, by way of displacing the normal bone
marrow cells with higher numbers of immature white blood cells, results
in a lack of blood platelets, which are important in the blood clotting process. This means people with leukemia may easily become bruised, bleed excessively, or develop pinprick bleeds (petechiae).
White blood cells, which are involved in fighting pathogens,
may be suppressed or dysfunctional. This could cause the person's
immune system to be unable to fight off a simple infection or to start
attacking other body cells. Because leukemia prevents the immune system
from working normally, some people experience frequent infection, ranging from infected tonsils, sores in the mouth, or diarrhea to life-threatening pneumonia or opportunistic infections.
Finally, the red blood cell deficiency leads to anemia, which may cause dyspnea and pallor.
Some people experience other symptoms, such as fevers, chills, night sweats, weakness in the limbs, feeling fatigued and other common flu-like symptoms. Some people experience nausea or a feeling of fullness due to an enlarged liver and spleen; this can result in unintentional weight loss. Blasts affected by the disease may come together and become swollen in the liver or in the lymph nodes causing pain and leading to nausea.
If the leukemic cells invade the central nervous system, then neurological symptoms (notably headaches) can occur. Uncommon neurological symptoms like migraines, seizures, or coma
can occur as a result of brain stem pressure. All symptoms associated
with leukemia can be attributed to other diseases. Consequently,
leukemia is always diagnosed through medical tests.
The word leukemia, which means 'white blood', is derived
from the characteristic high white blood cell count that presents in
most affected people before treatment. The high number of white blood
cells is apparent when a blood sample is viewed under a microscope,
with the extra white blood cells frequently being immature or
dysfunctional. The excessive number of cells can also interfere with the
level of other cells, causing further harmful imbalance in the blood
count.
Some people diagnosed with leukemia do not have high white blood
cell counts visible during a regular blood count. This less-common
condition is called aleukemia. The bone marrow still contains
cancerous white blood cells that disrupt the normal production of blood
cells, but they remain in the marrow instead of entering the
bloodstream, where they would be visible in a blood test. For a person
with aleukemia, the white blood cell counts in the bloodstream can be
normal or low. Aleukemia can occur in any of the four major types of
leukemia, and is particularly common in hairy cell leukemia.
Causes
Studies in 2009 and 2010 have shown a positive correlation between exposure to formaldehyde and the development of leukemia, particularly myeloid leukemia. The different leukemias likely have different causes.
Leukemia, like other cancers, results from mutations in the DNA. Certain mutations can trigger leukemia by activating oncogenes or deactivating tumor suppressor genes,
and thereby disrupting the regulation of cell death, differentiation or
division. These mutations may occur spontaneously or as a result of
exposure to radiation or carcinogenic substances.
Among adults, the known causes are natural and artificial ionizing radiation and petrochemicals, notably benzene and alkylating chemotherapy agents for previous malignancies. Use of tobacco is associated with a small increase in the risk of developing acute myeloid leukemia in adults. Cohort and case-control studies have linked exposure to some petrochemicals and hair dyes
to the development of some forms of leukemia. Diet has very limited or
no effect, although eating more vegetables may confer a small protective
benefit.
A few cases of maternal-fetal transmission (a baby acquires leukemia because its mother had leukemia during the pregnancy) have been reported. Children born to mothers who use fertility drugs to induce ovulation are more than twice as likely to develop leukemia during their childhoods than other children.
In a recent systematic review and meta-analysis of any type of leukemia in neonates using phototherapy, typically to treat neonatal jaundice,
a statistically significant association was detected between using
phototherapy and myeloid leukemia. However, it is still questionable
whether phototherapy is genuinely the cause of cancer or simply a result
of the same underlying factors that gave rise to cancer.
Radiation
Large doses of Sr-90 (called a bone seeking radioisotope) from nuclear reactor accidents, increases the risk of bone cancer and leukemia in animals and is presumed to do so in people.
Genetic conditions
Some
people have a genetic predisposition towards developing leukemia. This
predisposition is demonstrated by family histories and twin studies.
The affected people may have a single gene or multiple genes in common.
In some cases, families tend to develop the same kinds of leukemia as
other members; in other families, affected people may develop different
forms of leukemia or related blood cancers.
In addition to these genetic issues, people with chromosomal
abnormalities or certain other genetic conditions have a greater risk of
leukemia. For example, people with Down syndrome have a significantly increased risk of developing forms of acute leukemia (especially acute myeloid leukemia), and Fanconi anemia is a risk factor for developing acute myeloid leukemia. Mutation in SPRED1 gene has been associated with a predisposition to childhood leukemia.
Inherited bone marrow failure
syndromes represent a kind of premature aging of the bone marrow. In
people with these syndromes and in older adults, mutations associated
with clonal hematopoiesis may arise as an adaptive response to a progressively deteriorating hematopoietic niche, i.e., a depleting pool of Hematopoietic stem cells. The mutated stem cells then acquire a self-renewal advantage.
Chronic myelogenous leukemia is associated with a genetic abnormality called the Philadelphia translocation;
95% of people with CML carry the Philadelphia mutation, although this
is not exclusive to CML and can be observed in people with other types
of leukemia.
Non-ionizing radiation
Whether or not non-ionizing radiation causes leukemia has been studied for several decades. The International Agency for Research on Cancer expert working group undertook a detailed review of all data on static and extremely low frequency
electromagnetic energy, which occurs naturally and in association with
the generation, transmission, and use of electrical power. They concluded that there is limited evidence that high levels of ELF magnetic (but not electric) fields might cause some cases of childhood leukemia. No evidence for a relationship to leukemia or another form of malignancy in adults has been demonstrated. Since exposure to such levels of ELFs is relatively uncommon, the World Health Organization
concludes that ELF exposure, if later proven to be causative, would
account for just 100 to 2400 cases worldwide each year, representing 0.2
to 4.9% of the total incidence of childhood leukemia for that year
(about 0.03 to 0.9% of all leukemias).
Diagnosis is usually based on repeated complete blood counts and a bone marrow examination
following observations of the symptoms. Sometimes, blood tests may not
show that a person has leukemia, especially in the early stages of the
disease or during remission. A lymph node biopsy can be performed to diagnose certain types of leukemia in certain situations.
Following diagnosis, blood chemistry tests can be used to
determine the degree of liver and kidney damage or the effects of
chemotherapy on the person. When concerns arise about other damages due
to leukemia, doctors may use an X-ray, MRI, or ultrasound.
These can potentially show leukemia's effects on such body parts as
bones (X-ray), the brain (MRI), or the kidneys, spleen, and liver
(ultrasound). CT scans can be used to check lymph nodes in the chest, though this is uncommon.
Despite the use of these methods to diagnose whether or not a
person has leukemia, many people have not been diagnosed because many of
the symptoms are vague, non-specific,
and can refer to other diseases. For this reason, the American Cancer
Society estimates that at least one-fifth of the people with leukemia
have not yet been diagnosed.
Management of ALL is directed towards control of bone marrow and
systemic (whole-body) disease. Additionally, treatment must prevent
leukemic cells from spreading to other sites, particularly the central nervous system (CNS); periodic lumbar punctures are used for diagnostic purposes and to administer intrathecal prophylactic methotrexate. In general, ALL treatment is divided into several phases:
Induction chemotherapy to bring about bone marrow remission. For adults, standard induction plans include prednisone, vincristine, and an anthracycline drug; other drug plans may include L-asparaginase or cyclophosphamide.
For children with low-risk ALL, standard therapy usually consists of
three drugs (prednisone, L-asparaginase, and vincristine) for the first
month of treatment.
Consolidation therapy or intensification therapy to
eliminate any remaining leukemia cells. There are many different
approaches to consolidation, but it is typically a high-dose, multi-drug
treatment that is undertaken for a few months. People with low- to
average-risk ALL receive therapy with antimetabolite drugs such as methotrexate and 6-mercaptopurine (6-MP). People who are high-risk receive higher drug doses of these drugs, plus additional drugs.
CNS prophylaxis (preventive therapy) to stop cancer from spreading to the brain and nervous system in high-risk people. Standard prophylaxis may include radiation of the head and/or drugs delivered directly into the spine.
Maintenance treatments with chemotherapeutic drugs to prevent
disease recurrence once remission has been achieved. Maintenance
therapy usually involves lower drug doses and may continue for up to
three years.
Hematologists
base CLL treatment on both the stage and symptoms of the individual
person. A large group of people with CLL have low-grade disease, which
does not benefit from treatment. Individuals with CLL-related
complications or more advanced disease often benefit from treatment. In
general, the indications for treatment are:
Many different anti-cancer drugs are effective for the treatment of
AML. Treatments vary somewhat according to the age of the person and
according to the specific subtype of AML. Overall, the strategy is to
control bone marrow and systemic (whole-body) disease, while offering
specific treatment for the central nervous system (CNS), if involved.
In general, most oncologists rely on combinations of drugs for the initial, induction phase of chemotherapy. Such combination chemotherapy usually offers the benefits of early remission and a lower risk of disease resistance. Consolidation and maintenance
treatments are intended to prevent disease recurrence. Consolidation
treatment often entails a repetition of induction chemotherapy or the
intensification of chemotherapy with additional drugs. By contrast,
maintenance treatment involves drug doses that are lower than those
administered during the induction phase.
There are many possible treatments for CML, but the standard of care for newly diagnosed people is imatinib (Gleevec) therapy. Compared to most anti-cancer drugs, it has relatively few side effects and can be taken orally at home. With this drug, more than 90% of people will be able to keep the disease in check for at least five years, so that CML becomes a chronic, manageable condition.
In a more advanced, uncontrolled state, when the person cannot
tolerate imatinib, or if the person wishes to attempt a permanent cure,
then an allogeneic bone marrow transplantation may be performed. This
procedure involves high-dose chemotherapy and radiation followed by
infusion of bone marrow from a compatible donor. Approximately 30% of
people die from this procedure.
Decision to treat
People with hairy cell leukemia who are symptom-free typically do not
receive immediate treatment. Treatment is generally considered necessary
when the person shows signs and symptoms such as low blood cell counts
(e.g., infection-fighting neutrophil count below 1.0 K/μL), frequent
infections, unexplained bruises, anemia, or fatigue that is significant
enough to disrupt the person's everyday life.
Typical treatment approach
People who need treatment usually receive either one week of cladribine, given daily by intravenous infusion or a simple injection under the skin, or six months of pentostatin, given every four weeks by intravenous infusion. In most cases, one round of treatment will produce a prolonged remission.
Other treatments include rituximab infusion or self-injection with Interferon-alpha. In limited cases, the person may benefit from splenectomy (removal of the spleen).
These treatments are not typically given as the first treatment because
their success rates are lower than cladribine or pentostatin.
Most people with T-cell prolymphocytic leukemia, a rare and
aggressive leukemia with a median survival of less than one year,
require immediate treatment.
T-cell prolymphocytic leukemia is difficult to treat, and it does not respond to most available chemotherapeutic drugs. Many different treatments have been attempted, with limited success in certain people: purine analogues (pentostatin, fludarabine, cladribine), chlorambucil, and various forms of combination chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone CHOP, cyclophosphamide, vincristine, prednisone [COP], vincristine, doxorubicin, prednisone, etoposide, cyclophosphamide, bleomycin VAPEC-B). Alemtuzumab (Campath), a monoclonal antibody that attacks white blood cells, has been used in treatment with greater success than previous options.
Some people who successfully respond to treatment also undergo stem cell transplantation to consolidate the response.
The
success of treatment depends on the type of leukemia and the age of the
person. Outcomes have improved in the developed world. The average five-year survival rate is 65% in the United States. In children under 15, the five-year survival rate is greater (60 to 85%), depending on the type of leukemia. In children with acute leukemia who are cancer-free after five years, the cancer is unlikely to return.
Outcomes depend on whether it is acute or chronic, the specific abnormal white blood cell type, the presence and severity of anemia or thrombocytopenia, the degree of tissue abnormality, the presence of metastasis and lymph node and bone marrow
infiltration, the availability of therapies and the skills of the
health care team. Treatment outcomes may be better when people are
treated at larger centers with greater experience.
Epidemiology
Deaths due to leukemia per million persons in 2012
0–7
8–13
14–22
23–29
30–34
35–39
40–46
47–64
65–85
86–132
In 2010, globally, approximately 281,500 people died of leukemia. In 2000, approximately 256,000 children and adults around the world developed a form of leukemia, and 209,000 died from it.
This represents about 3% of the almost seven million deaths due to
cancer that year, and about 0.35% of all deaths from any cause. Of the sixteen separate sites the body compared, leukemia was the 12th most common class of neoplastic disease and the 11th most common cause of cancer-related death. Leukemia occurs more commonly in the developed world.
United States
About
245,000 people in the United States are affected with some form of
leukemia, including those that have achieved remission or cure. Rates
from 1975 to 2011 have increased by 0.7% per year among children. Approximately 44,270 new cases of leukemia were diagnosed in the year 2008 in the US.
This represents 2.9% of all cancers (excluding simple basal cell and
squamous cell skin cancers) in the United States, and 30.4% of all blood cancers.
Among children with some form of cancer, about a third have a type of leukemia, most commonly acute lymphoblastic leukemia.
A type of leukemia is the second most common form of cancer in infants
(under the age of 12 months) and the most common form of cancer in older
children.
Boys are somewhat more likely to develop leukemia than girls, and white
American children are almost twice as likely to develop leukemia than
black American children.
Only about 3% cancer diagnoses among adults are for leukemias, but
because cancer is much more common among adults, more than 90% of all
leukemias are diagnosed in adults.
More men than women are diagnosed with leukemia and die from the disease. Around 30 percent more men than women have leukemia.
Australia
In Australia, leukemia is the eleventh most common cancer.
In 2014–2018, Australians diagnosed with leukemia had a 64% chance (65%
for males and 64% for females) of surviving for five years compared to
the rest of the Australian population–there was a 21% increase in
survival rates between 1989–1993.
UK
Overall,
leukemia is the eleventh most common cancer in the UK (around 8,600
people were diagnosed with the disease in 2011), and it is the ninth
most common cause of cancer death (around 4,800 people died in 2012).
History
Rudolf Virchow
Leukemia was first described by anatomist and surgeon Alfred-Armand-Louis-Marie Velpeau in 1827. A more complete description was given by pathologist Rudolf Virchow in 1845. Around ten years after Virchow's findings, pathologist Franz Ernst Christian Neumann
found that the bone marrow of a deceased person with leukemia was
colored "dirty green-yellow" as opposed to the normal red. This finding
allowed Neumann to conclude that a bone marrow problem was responsible
for the abnormal blood of people with leukemia.
By 1900, leukemia was viewed as a family of diseases as opposed to a single disease. By 1947, Boston pathologist Sidney Farber believed from past experiments that aminopterin,
a folic acid mimic, could potentially cure leukemia in children. The
majority of the children with ALL who were tested showed signs of
improvement in their bone marrow, but none of them were actually cured.
Nevertheless, this result did lead to further experiments.
In 1962, researchers Emil J. Freireich, Jr. and Emil Frei III
used combination chemotherapy to attempt to cure leukemia. The tests
were successful with some people surviving long after the tests.
Etymology
Observing an abnormally large number of white blood cells in a blood sample from a person, Virchow called the condition Leukämie in German, which he formed from the two Greek words leukos (λευκός), meaning 'white', and haima (αἷμα), meaning 'blood'. It was formerly also called leucemia.
Society and culture
According to Susan Sontag,
leukemia was often romanticized in 20th-century fiction, portrayed as a
joy-ending, clean disease whose fair, innocent and gentle victims die
young or at the wrong time. As such, it was the cultural successor to tuberculosis, which held this cultural position until it was discovered to be an infectious disease. The 1970 romance novel Love Story is an example of this romanticization of leukemia.
In the United States, around $5.4 billion is spent on treatment a year.
Research directions
Significant
research into the causes, prevalence, diagnosis, treatment, and
prognosis of leukemia is being performed. Hundreds of clinical trials are being planned or conducted at any given time.
Studies may focus on effective means of treatment, better ways of
treating the disease, improving the quality of life for people, or
appropriate care in remission or after cures.
In general, there are two types of leukemia research: clinical or translational research and basic research.
Clinical/translational research focuses on studying the disease in a
defined and generally immediately applicable way, such as testing a new
drug in people. By contrast, basic science research studies the disease
process at a distance, such as seeing whether a suspected carcinogen
can cause leukemic changes in isolated cells in the laboratory or how
the DNA changes inside leukemia cells as the disease progresses. The
results from basic research studies are generally less immediately
useful to people with the disease.
Treatment through gene therapy is currently being pursued. One such approach used genetically modified T cells, known as chimeric antigen receptor T cells
(CAR-T cells), to attack cancer cells. In 2011, a year after treatment,
two of the three people with advanced chronic lymphocytic leukemia were
reported to be cancer-free
and in 2013, three of five subjects who had acute lymphocytic leukemia
were reported to be in remission for five months to two years. Subsequent studies with a variety of CAR-T types continue to be promising. As of 2018, two CAR-T therapies have been approved by the Food and Drug Administration. CAR-T treatment has significant side effects, and loss of the antigen targeted by the CAR-T cells is a common mechanism for relapse. The stem cells that cause different types of leukemia are also being researched.
Pregnancy
Leukemia is rarely associated with pregnancy, affecting only about 1 in 10,000 pregnant women.
How it is handled depends primarily on the type of leukemia. Nearly all
leukemias appearing in pregnant women are acute leukemias. Acute leukemias normally require prompt, aggressive treatment, despite significant risks of pregnancy loss and birth defects, especially if chemotherapy is given during the developmentally sensitive first trimester. Chronic myelogenous leukemia can be treated with relative safety at any time during pregnancy with Interferon-alpha hormones.
Treatment for chronic lymphocytic leukemias, which are rare in pregnant
women, can often be postponed until after the end of the pregnancy.
The carbon dioxide used to make synthetic fuels may be directly captured from the air, recycled from power plant flueexhaust gas or derived from carbonic acid in seawater. Common examples of synthetic fuels include ammonia and methane, although more complex hydrocarbons such as gasoline and jet fuel have also been successfully synthesized artificially. In addition to being carbon neutral, such renewable fuels can alleviate the costs and dependency issues of imported fossil fuels
without requiring either electrification of the vehicle fleet or
conversion to hydrogen or other fuels, enabling continued compatible and
affordable vehicles.
In order to be truly carbon-neutral, any energy required for the
process must be itself be carbon-neutral or emissions-free, like renewable energy or nuclear energy.
If the combustion of carbon-neutral fuels is subject to carbon capture at the flue, they result in net-negative carbon dioxide emission and may thus constitute a form of greenhouse gas remediation.
Negative emissions are widely considered an indispensable component of
efforts to limit global warming, although negative emissions
technologies are currently not economically viable for private sector
companies. Carbon credits are likely to play an important role for carbon-negative fuels.
Production of synthetic hydrocarbons
Synthetic hydrocarbons can be produced in chemical reactions between
carbon dioxide, which can be captured from power plants or the air, and hydrogen. The fuel, often referred to as electrofuel, stores the energy that was used in the production of the hydrogen.
Hydrogen fuel is typically prepared by the electrolysis of water in a power to gas process. To minimize emissions, the electricity is produced using a low-emission energy source such as wind, solar, or nuclear power.
There are a few more fuels that can be created using hydrogen. Formic acid for example can be made by reacting the hydrogen with CO2. Formic acid combined with CO2 can form isobutanol.
Methanol can be made from a chemical reaction of a carbon-dioxide
molecule with three hydrogen molecules to produce methanol and water.
The stored energy can be recovered by burning the methanol in a
combustion engine, releasing carbon dioxide, water, and heat. Methane can be produced in a similar reaction. Special precautions against methane leaks are important since methane is nearly 100 times as potent as CO2, regarding the 20-year global warming potential. More energy can be used to combine methanol or methane into larger hydrocarbon fuel molecules.
Researchers have also suggested using methanol to produce dimethyl ether.
This fuel could be used as a substitute for diesel fuel due to its
ability to self ignite under high pressure and temperature. It is
already being used in some areas for heating and energy generation. It
is nontoxic, but must be stored under pressure. Larger hydrocarbons and ethanol can also be produced from carbon dioxide and hydrogen.
All synthetic hydrocarbons are generally produced at temperatures of 200–300 °C, and at pressures of 20 to 50 bar. Catalysts
are usually used to improve the efficiency of the reaction and create
the desired type of hydrocarbon fuel. Such reactions are exothermic and
use about 3 mol of hydrogen per mole of carbon dioxide involved. They
also produce large amounts of water as a byproduct.
Sources of carbon for recycling
The most economical source of carbon for recycling into fuel is flue-gas emissions from fossil-fuel combustion where it can be obtained for about US$7.50 per ton.
However, this is not carbon-neutral, since the carbon is of fossil
origin, therefore moving carbon from the geosphere to the atmosphere.
Since carbonic acid in seawater is in chemical equilibrium with atmospheric carbon dioxide, extraction of carbon from seawater has been studied. Researchers have estimated that carbon extraction from seawater would cost about $50 per ton. Carbon capture from ambient air is more costly, at between $94 and $232 per ton and is considered impractical for fuel synthesis or carbon sequestration.
Direct air capture is less developed than other methods. Proposals for
this method involve using a caustic chemical to react with carbon
dioxide in the air to produce carbonates. These can then be broken down and hydrated to release pure CO2
gas and regenerate the caustic chemical. This process requires more
energy than other methods because carbon dioxide is at much lower
concentrations in the atmosphere than in other sources.
Researchers have also suggested using biomass as a carbon source
for fuel production. Adding hydrogen to the biomass would reduce its
carbon to produce fuel. This method has the advantage of using plant
matter to cheaply capture carbon dioxide. The plants also add some
chemical energy to the fuel from biological molecules. This may be a
more efficient use of biomass than conventional biofuel
because it uses most of the carbon and chemical energy from the biomass
instead of releasing as much energy and carbon. Its main disadvantage
is, as with conventional ethanol production, it competes with food
production.
Renewable and nuclear energy costs
Nighttime wind power is considered the most economical form of electrical power with which to synthesize fuel, because the load curve
for electricity peaks sharply during the warmest hours of the day, but
wind tends to blow slightly more at night than during the day.
Therefore, the price of nighttime wind power is often much less
expensive than any alternative. Off-peak wind power prices in high wind
penetration areas of the U.S. averaged 1.64 cents per kilowatt-hour in 2009, but only 0.71 cents/kWh during the least expensive six hours of the day. Typically, wholesale electricity costs 2 to 5 cents/kWh during the day. Commercial fuel synthesis companies suggest they can produce gasoline for less than petroleum fuels when oil costs more than $55 per barrel.
In 2010, a team of process chemists led by Heather Willauer of the U.S. Navy, estimates that 100 megawatts of electricity can produce 160 cubic metres (41,000 US gal) of jet fuel
per day and shipboard production from nuclear power would cost about
$1,600 per cubic metre ($6/US gal). While that was about twice the
petroleum fuel cost in 2010, it is expected to be much less than the
market price in less than five years if recent trends continue. Moreover, since the delivery of fuel to a carrier battle group costs about $2,100 per cubic metre ($8/US gal), shipboard production is already much less expensive.
Willauer said seawater is the "best option" for a source of synthetic jet fuel. By April 2014, Willauer's team had not yet made fuel to the standard required by military jets,
but they were able in September 2013 to use the fuel to fly a
radio-controlled model airplane powered by a common two-stroke internal
combustion engine.
Because the process requires a large input of electrical energy, a
plausible first step of implementation would be for American
nuclear-powered aircraft carriers (the Nimitz-class and the Gerald R. Ford-class) to manufacture their own jet fuel. The U.S. Navy is expected to deploy the technology some time in the 2020s.
In 2023, a study published by the NATO Energy Security Centre of
Excellence, concluded that e-fuels offer one of the most promising
decarbonization pathways for military mobility across the land, sea and
air domains.
Demonstration projects and commercial development
A 250 kilowatt methane synthesis plant was constructed by the Center for Solar Energy and Hydrogen Research (ZSW) at Baden-Württemberg and the Fraunhofer Society in Germany and began operating in 2010. It is being upgraded to 10 megawatts, scheduled for completion in autumn 2012.
Audi has constructed a carbon-neutral liquefied natural gas (LNG) plant in Werlte, Germany. The plant is intended to produce transportation fuel to offset LNG used in their A3 Sportback g-tron automobiles, and can keep 2,800 metric tons of CO2 out of the environment per year at its initial capacity.
Zero, a British-based company set up by former F1 engineer Paddy Lowe,
has developed a process it terms 'petrosynthesis' to develop synthetic
fuels from atmospheric carbon dioxide and water using renewable energy.
In 2022 it began work on a demonstration production plant at Bicester Heritage near Oxford.
Carbon-neutral
fuels can lead to greenhouse gas remediation because carbon dioxide gas
would be reused to produce fuel instead of being released into the
atmosphere. Capturing the carbon dioxide in flue gas emissions from
power plants would eliminate their greenhouse gas emissions, although
burning the fuel in vehicles would release that carbon because there is
no economical way to capture those emissions. This approach would reduce net carbon dioxide emission by about 50% if it were used on all fossil fuel power plants. Most coal and natural gas power plants have been predicted to be economically retrofittable with carbon dioxide scrubbers for carbon capture to recycle flue exhaust or for carbon sequestration. Such recycling is expected to not only cost less than the excess economic impacts of climate change if it were not done, but also to pay for itself as global fuel demand growth and peak oil shortages increase the price of petroleum and fungiblenatural gas.
Capturing CO2 directly from the air, known as direct air capture,
or extracting carbonic acid from seawater would also reduce the amount
of carbon dioxide in the environment, and create a closed cycle of
carbon to eliminate new carbon dioxide emissions.
Use of these methods would eliminate the need for fossil fuels
entirely, assuming that enough renewable energy could be generated to
produce the fuel. Using synthetic hydrocarbons to produce synthetic
materials such as plastics could result in permanent sequestration of
carbon from the atmosphere.
Some authorities have recommended producing methanol
instead of traditional transportation fuels. It is a liquid at normal
temperatures and can be toxic if ingested. Methanol has a higher octane rating than gasoline but a lower energy density,
and can be mixed with other fuels or used on its own. It may also be
used in the production of more complex hydrocarbons and polymers. Direct
methanol fuel cells have been developed by Caltech's Jet Propulsion Laboratory to convert methanol and oxygen into electricity.
It is possible to convert methanol into gasoline, jet fuel or other
hydrocarbons, but that requires additional energy and more complex
production facilities.
Methanol is slightly more corrosive than traditional fuels, requiring
automobile modifications on the order of US$100 each to use it.
Fuel made from microalgae
could potentially have a low carbon footprint and is an active area of
research, although no large-scale production system has been
commercialized to date. Microalgae are aquatic unicellular organisms. Although they, unlike most plants, have extremely simple cell structures, they are still photoautotrophic, able to use solar energy to convert carbon dioxide into carbohydrates and fats via photosynthesis. These compounds can serve as raw materials for biofuels like bioethanol or biodiesel. Therefore, even though combusting
microalgae-based fuel for energy would still produce emissions like any
other fuel, it could be close to carbon-neutral if they, as a whole,
consumed as much carbon dioxide as is emitted during combustion.
The advantages of microalgae are their higher CO2-fixation efficiency compared to most plants and their ability to thrive in a wide variety of aquatic habitats.
Their main disadvantage is their high cost. It has been argued that
their unique and highly variable chemical compositions may make it
attractive for specific applications.
Microalgae also can be used as livestock feed due to their proteins. Even more, some species of microalgae produce valuable compounds such as pigments and pharmaceuticals.
Production
Raceway pond used for the cultivation of microalgae. The water is kept in constant motion with a powered paddle wheel.
Two main ways of cultivating microalgae are raceway pond systems and
photo-bioreactors. Raceway pond systems are constructed by a closed loop
oval channel that has a paddle wheel to circulate water and prevent
sedimentation. The channel is open to the air and its depth is in the
range of 0.25–0.4 m (0.82–1.31 ft).
The pond needs to be kept shallow since self-shading and optical
absorption can cause the limitation of light penetration through the
solution of algae broth. PBRs's culture medium is constructed by closed
transparent array of tubes. It has a central reservoir which circulated
the microalgae broth. PBRs is an easier system to be controlled compare
to the raceway pond system, yet it costs a larger overall production
expenses.[citation needed]
The carbon emissions from microalgae biomass produced in raceway
ponds could be compared to the emissions from conventional biodiesel by
having inputs of energy and nutrients as carbon-intensive.
The corresponding emissions from microalgae biomass produced in PBRs
could also be compared and might even exceed the emissions from
conventional fossil diesel. The inefficiency is due to the amount of
electricity used to pump the algae broth around the system. Using
co-product to generate electricity is one strategy that might improve
the overall carbon balance. Another thing that needs to be acknowledged
is that environmental impacts can also come from water management,
carbon dioxide handling, and nutrient supply, several aspects that could
constrain system design and implementation options. But, in general,
Raceway Pond systems demonstrate a more attractive energy balance than
PBR systems.
Economy
Production
cost of microalgae-biofuel through implementation of raceway pond
systems is dominated by the operational cost which includes labour, raw
materials, and utilities. In raceway pond system, during the cultivation
process, electricity takes up the largest energy fraction of total
operational energy requirements. It is used to circulate the microalgae
cultures. It takes up an energy fraction ranging from 22% to 79%.
In contrast, capital cost dominates the cost of production of
microalgae-biofuel in PBRs. This system has a high installation cost
though the operational cost is relatively lower than raceway pond
systems.
Microalgae-biofuel production costs a larger amount of money
compared to fossil fuel production. The cost estimation of producing
microalgae-biofuel is around $3.1 per litre ($11.57/US gal),
which is considerably more expensive than conventional gasoline.
However, when compared with electrification of the vehicle fleet – a key
advantage of such biofuel is the avoidance of the costly distribution
of large amounts of electrical energy (as is required to convert
existing vehicle fleets to battery electric technology), therein
allowing for the re-use of the existing liquid-fuel transportation
infrastructure. Biofuel such as ethanol is also greatly more energy
dense than current battery technologies (approximately 6x as much) further promoting its economic viability.
Environmental impact
The
construction of large-scale microalgae cultivation facilities would
inevitably result in negative environmental impacts related to land use change,
such as the destruction of existing natural habitats. Microalgae can
also under certain conditions emit greenhouse gases, like methane or nitrous oxide, or foul-smelling gases, like hydrogen sulfide,
although this has not been widely studied to date. If poorly managed,
toxins naturally produced by microalgae may leak into the surrounding
soil or ground water.
Production
Water
undergoes electrolysis at high temperatures to form hydrogen gas and
oxygen gas. The energy to perform this is extracted from renewable
sources such as wind power. Then, the hydrogen is reacted with
compressed carbon dioxide captured by direct air capture.
The reaction produces blue crude which consists of hydrocarbon. The
blue crude is then refined to produce high efficiency E-diesel.
This method is, however, still debatable because with the current
production capability it can only produce 3,000 liters in a few months,
0.0002% of the daily production of fuel in the US.
Furthermore, the thermodynamic and economic feasibility of this
technology have been questioned. An article suggests that this
technology does not create an alternative to fossil fuel but rather
converting renewable energy into liquid fuel. The article also states
that the energy return on energy invested using fossil diesel is 18
times higher than that for e-diesel.
History
Investigation
of carbon-neutral fuels has been ongoing for decades. A 1965 report
suggested synthesizing methanol from carbon dioxide in air using nuclear
power for a mobile fuel depot. Shipboard production of synthetic fuel using nuclear power was studied in 1977 and 1995. A 1984 report studied the recovery of carbon dioxide from fossil fuel plants. A 1995 report compared converting vehicle fleets for the use of carbon-neutral methanol with the further synthesis of gasoline.
