Toxicological Profile for Xylenes Available from ATSDR
The Agency for Toxic Substances and Disease Registry has released a toxicological profile for xylenes, which ATSDR describes as highly flammable, colorless liquids with a sweet odor. Xylenes are present in the environment and are released naturally during wildfires. They are also found in cigarette smoke and vehicle exhaust. Xylene sold commercially is typically a mixture of three isomers called ortho-xylene, meta-xylene, and para-xylene, which are used in the production of paints, coatings, and pesticides, according to ATSDR.
Exposure to xylenes occurs primarily in work environments such as petrochemical refineries; facilities that manufacture adhesives, paints, and coatings; and hazardous waste sites. People who live near these workplaces may also be exposed. The main routes of exposure are inhalation and ingestion. Dermal exposure could not be quantified, ATSDR explains, though it may be significant following contact with liquid xylenes.
The health effects of xylenes exposure include neurological symptoms such as dizziness, headache, anxiety, forgetfulness, and dimmed vision, as well as respiratory symptoms such as throat or airway discomfort, nasal irritation, and difficulty breathing. The potential for xylenes to cause cancer has not been well studied, ATSDR states. The International Agency for Research on Cancer has determined that the carcinogenicity of xylenes is “not classifiable.”
ATSDR has determined minimal risk levels (MRLs) for both inhalation and ingestion of xylenes. An appendix in the toxicological profile defines an MRL as “an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse noncancer health effects over a specified route and duration of exposure.” ATSDR uses MRLs “to identify contaminants and potential health effects that may be of concern at hazardous waste sites.” They are derived from no observed adverse effect levels (NOAELs) and the application of uncertainty factors, and they are intended as screening levels, not action levels, the agency states.
The toxicological profile for xylenes presents provisional inhalation MRLs of 2 ppm (9 mg/m3) for acute durations (1–14 days), 0.4 ppm (2 mg/m3) for intermediate durations (15–364 days), and 0.01 ppm (0.04 mg/m3) for chronic durations (greater than 364 days). The provisional oral MRLs are 1 mg/kg/day for acute durations and 0.2 mg/kg/day for both intermediate and chronic durations.
The toxicological profile for xylenes is available as a PDF from ATSDR. For more information on xylenes, see the NIOSH and OSHA websites.