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From Valor, I., In Handbook of Water Analysis, Nollet, Leo, M. L., Ed., Marcel Dekker, New York, 2000. With permission.

From Valor, I., In Handbook of Water Analysis, Nollet, Leo, M. L., Ed., Marcel Dekker, New York, 2000. With permission.

Some aspects of how the different BTEX compounds can affect human health follow.

Benzene. Benzene is recognized as the most toxic compound among BTEX, because it has been proved that breathing very high concentrations of benzene in air can cause death and that long-term exposure to lower levels causes leukemia. The Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 1 ppm in the workplace during an 8-h day if 40 h a week are worked.

For water, the U.S. Environmental Protection Agency (EPA) has set the maximum permissible level for benzene in drinking water at 5 mg/l, while in Europe a maximum concentration of 1 mg/l is permitted.

In air, the maximum limit recommended by the European Community is 10 mg/l.

Toluene. Compared to benzene, toluene's toxicity is very low. Whereas very high concentration exposures are needed to cause death, moderate ones may affect the nervous system. There is no evidence for the carcinogenicity of toluene. For air, the OSHA has set a limit of 200 ppm in the workplace and the EPA's drinking water limit is set at 1 mg/l.

Ethylbenzene. Ethylbenzene's toxicity is low and there is no evidence that it causes cancer. EPA drinking water and OSHA occupational exposure limits are set at 0.7 mg/l and 100 ppm (8 h/day per 40 h/week), respectively.

Xylenes. Like toluene, high concentration exposures to xylene can cause death, while moderate ones can affect the brain. No evidence for the carcinogenicity of xylene is found. EPA drinking water and OSHA occupational exposure limits are set at 10 and 100 ppm (8 h/day per 40 h/week), respectively.

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