Men who breathe in formaldehyde fumes as part of their jobs have triple the average risk of developing the paralyzing disease ALS, researchers reported Monday.
Funeral directors who use formaldehyde to embalm bodies may be the most at risk, the researchers at the Harvard School of Public Health found.
Their findings, published in the Journal of Neurology Neurosurgery & Psychiatry, strengthen the links between formaldehyde and amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease. The condition, which gradually paralyzes patients by damaging their nerves, affects an estimated 30,000 Americans. It's always fatal.
Veterans carry a higher-than-average risk, for reasons not fully understood.
Andrea Roberts and colleagues at Harvard used a database of nearly 1.5 million people from 1973 followed until they died. Each person filled out a survey at least once about his or her job.
Based on this, the calculated whether each person was likely to have been exposed to formaldehyde at work.
Formaldehyde is used to make particle board and other wood products, in some glues, as a preservative in shampoo and sometimes to make permanent press fabrics. It also preserves tissue and is used to store some biological samples and in mortuaries. The federal government has classified it as a probable human carcinogen at high exposures.
Men with a high probability of formaldehyde exposure were three times as like to have died of ALS as men with no probable exposure, they found. There were not enough women with a job that made them to breathe in formaldehyde to calculate a risk.
Formaldehyde is known to damage nerves in several different ways, but studies seeking to link ALS to embalming fluid have had mixed results.
Only two men who died had a high probability of formaldehyde exposure at high levels and both were funeral directors, Roberts and colleagues wrote. Most of the ALS deaths were in people with no probable exposure to formaldehyde - 372 in total.
"Our results should be interpreted cautiously," the researchers added. "Jobs involving both high probability and high intensity of formaldehyde are relatively uncommon in the USA, and ALS is also rare; there were only two ALS deaths among men in such jobs," they wrote.
But they said it's worth looking at more closely.