Shortly after taking office, President Bush caused an uproar when he suspended a Clinton administration rule setting a tougher standard for arsenic -- a poison at high concentrations and a carcinogen at lower ones -- in drinking water systems. Congress quickly reinstated the rule.

Now the Environmental Protection Agency is again proposing to let rural water systems save their customers money by providing water with three times as much arsenic as the Clinton rule permits. At the same time, the agency is proposing weaker air-quality standards that would let oil refineries, chemical plants, hazardous waste incinerators, and other facilities emit greater amounts of toxic pollutants such as lead, mercury, and -- again -- arsenic. According to an internal EPA memo in December, seven of the EPA's 10 regional offices said the proposed rule would let polluters ''virtually avoid regulation and greatly complicate any enforcement."

The drinking water rule would affect systems serving 10,000 or fewer people, and would permit higher levels of other contaminants as well. In the case of arsenic, which occurs naturally in many water systems and is also spread by industrial pollution, about 10 million people would be drinking water that does not meet the tougher standard, which went into effect in January.

Soon after the Bush administration first suspended the Clinton rule in 2001, the National Academy of Sciences reported that arsenic was even more dangerous than indicated in previous studies that had formed the basis for the Clinton rule. That report, requested by then-EPA head Christine Whitman, bolstered the belief of clean-water advocates that even the Clinton rule was too weak. The EPA proposal to permit arsenic levels as high as 30 parts per billion -- three times the Clinton rule limit -- is an open invitation for increased incidence of bladder and lung cancers.

Decontaminating drinking water and reducing air pollution both cost money. But opinion polls consistently show that the public wants the investments made, even at the cost of higher water bills or gasoline prices, if the alternative is more cancer-causing pollutants in the environment or, in the case of lead and mercury, severe neurological conditions. The EPA should insist on the Clinton rule, or an even tougher one, for drinking water. And it should drop its proposal to move away from the requirement of maximum achievable technology to control heavy airborne emitters of lead, mercury, and arsenic.