Concerning new research suggests funeral directors who use formaldehyde-rich embalming fluid to prepare bodies could have a heightened risk of developing ALS.

ALS, also known as Lou Gehrig's disease, was highly publicized in last year's ice bucket challenge. It causes "muscle weakness, paralysis, and eventually respiratory failure and death," and there is currently no cure, the British Medical Journal reported.

A team of researchers used the U.S. National Longitudinal Mortality Study (NLMS), to study links between death from ALS and occupational exposure to formaldehyde. In the study, which included over 1.5 million adults, participants over the age of 25 were asked about their current or most recent occupation. The researchers then estimated their average formaldehyde exposure using criteria developed by industrial hygienists at the National Cancer Institute.

The findings revealed men in professions with a high probability of exposure to formaldehyde were about three times more likely to die from ALS than those who had not been exposed to the chemical at all. Men whose intensity and probability of exposure were rated as high were over four times more likely to die from ALS than those with no exposure. All of the 493 men with high intensity and probability of formaldehyde exposure were funeral directors. 

On the other hand, women who had a higher estimated exposure to the chemical did not have a higher risk of death from ALS. The researchers noted the disparity may be due to the fact that fewer women have these types of jobs, making their risk more difficult to calculate. Another factor could be that women funeral directors are more often tasked with dealing with grieving relatives rather than directly working in embalming.

The study was exclusively observational, so a definitive conclusion cannot yet be drawn regarding cause and effect. Funeral directors are also exposed to a number of other bacteria and prions that could potentially have an influence on ALS risk. Despite these factors, past studies have linked formaldehyde to nerve damage. They have also shown the chemical increased the permeability of cell mitochondria as well as free radical production, all of which could have a negative effect on ALS risk.

"Adequate preparation room ventilation is the most effective way of reducing formaldehyde exposure," the National Funeral Directors Association stated, according to CBS News.

The findings were published in a recent edition of the Journal of Neurology, Neurosurgery & Psychiatry.