Formaldehyde has long been linked to rare tumors of the nasopharynx, which includes the back of the throat, which affect about 2,000 AMericans a year, according to the American Cancer Society.
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The new study — the largest to date on workplace exposures — provides further evidence linking formaldehyde with cancers of the blood and lymphatic system. These cancers are far more common, affecting nearly 140,000 AMericans a year.
In the study, scientists from the National Cancer Institute followed 25,000 workers for a median of 42 years, estimating the amount of formaldehyde to which each person was exposed on the job. Among other things, scientists compared workers' "peak" exposures to formaldehyde, or the greatest single dose they might encounter at one time.
Workers with the highest peak exposures were 37% more likely to die from any blood or lymphatic cancer, and 78% more likely to die from myeloid leukemia — a cancer of the white blood cells — compared to those with lowest levels, according to the study, published online today in the Journal of the National Cancer Institute.
Highly exposed workers also were nearly four times more likely to die of Hodgkin lymphoma, which affects immune cells, the study shows. This study is the first to link a chemical with an increased risk of death from Hodgkin lymphoma, according to the NCI.
The overall risk of death from these cancers was relatively low, causing only 319 of the 14,000 deaths during the study, says author Laura Beane Freeman, an NCI scientist.
More than 2 million Americans are exposed to formaldehyde in the workplace, the study says.
Freeman says her study doesn't allow her to estimate the risk of formaldehyde exposure to the general public.
But the cancer society's Elizabeth Ward notes that exposure to formaldehyde, which can seep out of wood and other products to pollute indoor air, is "ubiquitous."
Dangerously high formaldehyde levels have been found in trailers provided by the Federal Emergency Management Agency to Gulf Coast residents displaced by Hurricane Katrina. A March report from the Campaign for Safe Cosmetics, an environmental advocacy group, also found formaldehyde in more than 80% of bath and shampoos tested.
The Environmental Protection Agency listed formaldehyde as a "probable human carcinogen" in 1987. In 2004, the International Agency for Research on Cancer went further, classifying formaldehyde as a "known human carcinogen" based partly on research suggesting a link to leukemia.