2-Methylnaphthalene is one of over 100 different polycyclic aromatic hydrocarbons (PAHs). PAHs are chemicals that are formed during the incomplete burning organic substances, such as fossil fuels. They are usually found as a mixture containing two or more of these compounds. (4)
belongs to the class of organic compounds known as naphthalenes. Naphthalenes are compounds containing a naphthalene moiety, which consists of two fused benzene rings.
The ability of PAH's to bind to blood proteins such as albumin allows them to be transported throughout the body. Many PAH's induce the expression of cytochrome P450 enzymes, especially CYP1A1, CYP1A2, and CYP1B1, by binding to the aryl hydrocarbon receptor or glycine N-methyltransferase protein. These enzymes metabolize PAH's into their toxic intermediates. The reactive metabolites of PAHs (epoxide intermediates, dihydrodiols, phenols, quinones, and their various combinations) covalently bind to DNA and other cellular macromolecules, initiating mutagenesis and carcinogenesis. (4, 6, 2, 3)
Metabolism
PAH metabolism occurs in all tissues, usually by cytochrome P-450 and its associated enzymes. PAHs are metabolized into reactive intermediates, which include epoxide intermediates, dihydrodiols, phenols, quinones, and their various combinations. The phenols, quinones, and dihydrodiols can all be conjugated to glucuronides and sulfate esters; the quinones also form glutathione conjugates. (4)
Not directly listed by IARC. 2-Methylnaphthalene is found in coal tar mixtures, and occupational exposures during coal-tar distillation and during paving and roofing with coal-tar pitch are classified as carcinogenic to humans (Group 1). (7)
Uses/Sources
PAHs are released into the environment via the combustion of fossil fuels, coke oven emissions and vehicle exhausts, as well as naturally from forest fires and voLcanic eruptions. PAHs from these sources may contaminate nearly water systems. They are also found in coal tar and charbroiled food. 2-Methylnaphthalene is used to make other chemicals such as dyes and resins. (4, 5)
Minimum Risk Level
Not Available
Health Effects
PAHs are carcinogens and have been associated with the increased risk of skin, respiratory tract, bladder, stomach, and kidney cancers. They may also cause reproductive effects and depress the immune system. Exposure to large amounts of 2-methylnapthalene may damage or destroy the red blood cells, resulting in hemolytic anemia. (4, 5)
Symptoms
Acute exposure to PAHs causes irritation and inflammation of the skin and lung tissue. Some symptoms of hemolytic anemia are fatigue, lack of appetite, restlessness, and pale skin. Exposure to large amounts of 2-methylnapthalene may also cause nausea, vomiting, diarrhea, blood in the urine, and a yellow color to the skin. (1, 5)
Treatment
There is no known antidote for PAHs. Exposure is usually handled with symptomatic treatment. (4)
