Exceedance of the RfD does not imply that an adverse health effect would necessarily occur. As the amount and frequency of exposures exceeding the RfD increase, the probability of adverse health effects also increases. The principal route of human exposure to methylene chloride is inhalation of ambient air. People who work in these places can breathe in the chemical or it may come in contact with the skin. Methylene chloride has been detected in both surface water and groundwater samples taken at hazardous waste sites and in drinking water at very low concentrations.
Several tests exist for determining exposure to methylene chloride.
These tests include direct measurement of methylene chloride in the air and analysis of methylene chloride present in the blood and urine. It is noted that smoking and exposure to other chemicals may affect the results of these tests. Acute inhalation exposure to high levels of methylene chloride in humans has resulted in effects on the nervous system including decreased visual and auditory functions, but these effects are reversible once exposure ceases. Methylene chloride also irritates the nose and throat at high concentrations. Animal studies indicate that the inhalation of methylene chloride causes effects on the liver, kidney, and cardiovascular system.