Lou Gehrig's Disease is a progressive, usually fatal, neurodegenerative disease caused by the degeneration of motor neurons, the nerve cells in the central nervous system that control voluntary muscle movement. As a motor neuron disease, the disorder causes muscle weakness and atrophy throughout the body as both the upper and lower motor neurons degenerate, ceasing to send messages to muscles. Unable to function, the muscles gradually weaken, develop fasciculations (twitches) because of denervation, and eventually atrophy due to that denervation. The patient may ultimately lose the ability to initiate and control all voluntary movement except of the eyes.
The ALS Association estimated that about 5,600 people in the United States are diagnosed with ALS each year.
Researchers studied the link between ALS and 12 types of chemicals. At first the study was devoted to the effect of pesticides and herbicides, but later it was discovered that formaldehyde increased the risk for developing the disease.
The study showed that those people who were regularly exposed to the chemical were 34 percent more likely to develop ALS compared to those exposed to other chemicals (for example, 10 or more years of exposure increased the risk almost four times).
At concentrations above 0.1 ppm in air formaldehyde can irritate the eyes and mucous membranes, resulting in watery eyes. Formaldehyde inhaled at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, as well as triggering or aggravating asthma symptoms.
Formaldehyde is classified as a probable human carcinogen by the U.S. Environmental Protection Agency. The International Agency for Research on Cancer (IARC) has determined that there is "sufficient evidence" that occupational exposure to formaldehyde causes nasopharyngeal cancer in humans. The United States Environmental Protection Agency USEPA allows no more than 0.016 ppm formaldehyde in the air in new buildings constructed for that agency.