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DBCP In Drinking Water: What Does It Mean? Page 4 MALE FERTILITY In 1977 men working in two DBCP formulating plants were found to be incapable of producing sperm, or to have sperm levels that were very low. In the California plant, 14 out of 25 men were affected, and in an Arkansas plant, half of 106 workers were affected. In most cases, the men regained their fertility after their exposure to the chemical was stopped. A few men with the longest exposures remained permanently sterile. The workers in the plants were exposed to DBCP mainly by breathing the chemicals in the air as well as skin contact. the amount of DBCP workers were exposed to was many times higher than amounts present in drinking water. HOW WILL THE STATE STANDARD FOR DBCP PROTECT MY HEALTH? The maximum contaminant level (MCL) for DBCP is 0.2 ppb. This is the same as 0.2 micrograms per liter (ug/L) or 0.0002 parts per million (ppm). A part per billion means 1 part of chemical per billion parts of water. The levels of DBCP found in California drinking water supplies usually do not exceed 10 ppb. The earlier 1 ppb action level set in 1979 was based primarily on the minimum concentration of DBCP that could be detected in drinking water with the analytical means available at that time. This level was also then considered adequate for protecting public health and economically feasible to attain. Action levels are not legally enforceable, but water utilities have voluntarily complied with them. The 0.2 ppb MCL for DBCP is based on a cost -benefit analysis that considered the benefits of providing cancer protection versus the costs of removing the chemical, as explained further below. DHS has calculated that 0.4 ppb DBCP in drinking water represents a level of exposure at which no effect on fertility in humans would be expected (in fact, this level includes a very large safety margin), so cancer risk is the main health effect of concern. With cancer-causing chemicals, no levels can be considered completely safe. This is because of the way these chemicals act on animals, which is different from other kinds of toxicants. Some degree of risk is believed to exist no matter how small the dose. Federal and state agencies use risk assessment to estimate the cancer risk presented by a hazardous contaminant and then try to reduce the risk as close as possible to a negligible level through regulatory controls. A negligible level is usually considered to be a level between 1 in 100,000 and 1 in 1 million additional cancer cases for a lifetime exposure (70years). Once the negligible risk level has been estimated, economic costs and technological feasibility are taken into account. In case of DBCP the high economic costs of removal do not allow the negligible risk level to be achieved. The estimated risk is 1 in 10,000. This means that if 10,000 people were each to drink 2 liters of water a day containing