A review of human carcinogens

In October 2009, 23 scientists from 6 countries met at the International Agency
for Research on Cancer (IARC) to re-assess the carcinogenicity of a number of
chemical compounds, complex mixtures and occupational exposures previously
classified as carcinogenic to humans (Group 1) and to identify additional
tumour sites and mechanisms of carcinogenesis. These assessments will be
published as the sixth and last part of Volume 100 of the IARC Monographs.
Dioxin (2,3,7,8-TCDD), now has sufficient evidence in humans. The Working Group
extended the Group-1 classification to 2,3,4,7,8-pentachlorodibenzofuran and
3,4,5,3',4'pentachlorobiphenyl, which are indicator chemicals for a larger
class of dioxin-like chlorinated dibenzofurans and dioxin-like polychlorinated
biphenyls (PCBs).

Formaldehyde was confirmed as carcinogenic to humans. There is sufficient
evidence in humans of an increased incidence of nasopharyngeal Carcinomas. In
addition, the epidemiological evidence on leukemia has become stronger, and new
mechanistic studies support a conclusion of sufficient evidence in humans. This
highlights the value of mechanistic studies, which in only 5 years have
replaced previous assertions of biological implausibility with new evidence
that formaldehyde can cause blood-cell abnormalities that are characteristic of
leukemia development.

Occupational exposure as a painter causes cancers of the lung, urinary bladder
and pleural mesothelioma in humans. Due to the diversity and complexity of the
exposures, it is difficult to identify causal agents or a causal mechanism,
although there is strong evidence that the exposures are genotoxic. The Working
Group found limited evidence of an association between maternal exposure to
painting before and during pregnancy and an increased risk of childhood
leukemia in the offspring. These findings confirm those of a previous Working
Group (2007).

More information: - Source: European Agency for Safety and Health at Work