The control of organics in drinking water in Canada and the United States (standards, legislation and practice).

Both the United States and Canada have a federal form of government, but approaches used in the two countries to ensure the safety of drinking water supplies differ. The Environmental Protection Agency currently enforces regulations for 10 organic chemicals (including 6 pesticides) under the Safe Drinking Water Act and provides advice on others through its health advisory program. Canada, however, does not have similar legislation, but rather provides health-related guidelines for 21 organic chemicals (including 16 pesticides) which are used by the provincial agencies responsible for drinking water supplies. Both countries are in the process of revising their standards and will include a variety of additional synthetic organic chemicals. Where possible, standards are set using a calculated acceptable daily intake usually derived from animal feeding experiments. Procedures for setting standards for carcinogens involve a blend of risk estimation coupled with consideration of the feasibility of reducing the risk in light of socio-economic factors. Most drinking water treatment plans in North America utilize 'conventional' treatment. Some now employ modifications in order to minimize trihalomethane formation. A few use aeration or granular activated carbon to remove synthetic organic chemicals.