The International Agency for Research on Cancer (or IARC) is an arm of
the World Health Organization that is charged with investigating cancer,
and particularly the disease's causes. IARC reviews scientific research
discussing various chemicals, and issues publications called monographs
describing its review and findings.
In 1982, IARC issued Volume 29 of its monographs, which discussed a number
of industrial chemicals, including benzene. Benzene is a powerful solvent
that was used in industry for decades, and which is also present in other
solvent products, such as toluene and xylene, as well as in gasoline and
diesel fuel. At the time, IARC concluded that "[i]t is established
that human exposure to commercial benzene or benzene-containing mixtures
can cause damage to the haematopoetic [blood-forming] system, including
pancytopenia." International Agency for Research on Cancer, World
Health Organization, "Benzene,"
in Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to
Humans, Vol. 29: Some Industrial Chemicals and Dyestuffs, p. 127 (1982).
IARC went on to find that "[t]he relationship between benzene exposure
and the development of acute myelogenous leukaemia has been established
in epidemiological studies." However, IARC noted that "[r]eports
linking exposure to benzene with other malignancies were considered to
be inadequate for evaluation." Nevertheless, IARC determined that
"[t]here is sufficient evidence that benzene is carcinogenic to man."
This year, IARC published an updated evaluation of benzene. IARC reaffirmed
its previous finding that benzene is carcinogenic, observing unequivocally
that "[b]enzene causes acute myeloid leukaemia/acute non-lymphocytic
leukaemia." International Agency for Research on Cancer, World Health
Organization, "Benzene,"
in Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to
Humans, Vol. 100F: Chemical Agents and Related Occupations, p. 285 (2012). In its updated monograph, however, IARC also found that
"a positive association has been observed between exposure to benzene
and acute lymphocytic leukaemia, multiple myeloma, and non-Hodgkin lymphoma."
A link to IARC's 2012 monograph can be found
here.
IARC's finding follows the German government's determination that
all diseases of the blood, hematopoietic (blood-forming), and lymphatic
systems can be caused by occupational benzene exposure. Beelte, S.,
et al., "Paradigm Change in the Assessment of Myeloid and Lymphoid Neoplasms
Associated with Occupation Benzene Exposure (OD Number 1303)."
Medizinische Klinik [Medical Clinic] 104(3):197-203 (2009). Notably, the German government did not limit its
consideration of benzene exposure to use of benzene itself. Rather, it
found that occupational exposure to products such as fuels and spray coatings
could lead to benzene exposure.
Additionally, in 2010 the President's Cancer Panel, an advisory group
created by federal law as part of the National Cancer Program, published
a report titled
Reducing Environmental Cancer Risk: What We Can Do Now. In its report, the Panel found strong evidence of a link between benzene
exposure and leukemia, multiple myeloma, and non-Hodgkin's lymphoma.
President's Cancer Panel,
Reducing Environmental Cancer Risk: What We Can Do Now, p. A-43 (2010). A link to the President's Cancer Panel report can be found
here.
Even more recently, in 2012, an international research team evaluated a
group of 17 scientific studies dating back to 1993, and found "support
for a possible association of occupational exposure to benzene and the
risk of CML," adding chronic myelogenous leukemia to the list of
diseases linked to benzene exposure. Vlaanderen, J.,
et al., "Occupational Benzene Exposure and the Risk of Chronic Myeloid Leukemia:
A Meta-Analysis of Cohort Studies Incorporating Study Quality Dimensions."
Amer. J. Indus. Med. 55:779-85 (2012).
While benzene has long been associated with diseases of the blood and blood-forming
system, much of the strongest evidence has historically focused one disease---acute
myelogenous leukemia. However, a mounting body of scientific evidence
is tying exposure to benzene---including exposures from products of which
benzene makes up only a small part---to virtually all blood diseases,
including not just AML, but also multiple myeloma, non-Hodgkin's lymphoma,
acute lymphocytic leukemia, and chronic myelogenous leukemia.