Occupational exposure to formaldehyde by inhalation is mainly from three types of sources: thermal or chemical decomposition of formaldehyde-based resins, formaldehyde emission from aqueous solutions (for example, embalming fluids), and the production of formaldehyde resulting from the combustion of a variety of organic compounds (for example, exhaust gases). Formaldehyde can be toxic, allergenic, and carcinogenic.[7] Because formaldehyde resins are used in many construction materials, formaldehyde is one of the more common indoor air pollutants.[citation needed] At concentrations above 0.1 ppm in air, formaldehyde can irritate the eyes and mucous membranes, resulting in watery eyes. If inhaled, formaldehyde at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, as well as triggering or aggravating asthma symptoms.[8] Formaldehyde is classified as a probable human carcinogen by the U.S. Environmental Protection Agency, which provides sufficient evidence that formaldehyde causes nasopharyngeal cancer in humans by the International Agency for Research on Cancer.[9] 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[10] Formaldehyde can cause allergies, and is part of the standard patch test series. People with formaldehyde allergy are advised to avoid formaldehyde-releasing chemicals as well (e.g. Quaternium-15, imidazolidinyl urea, and diazolidinyl urea).[11] Formaldehyde has been banned in cosmetics in both Sweden and Japan.
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