The United States Senate rejected a move today by Senator James Inhofe (R.-Oklahoma) to bar implementation of a new rule that will require coal- and oil-fired power plants to reduce mercury emissions by as much as 90% starting in 2015.

The vote was 53 to 46.

The rule is called “Utility MACT” by the environmental community.

Critics charge that the rule will impose too great an economic cost on the parts of the United States that rely on coal to generate electricity.

The vote was largely along party lines, with five Democrats joining 41 Republicans in voting to override the Environmental Protection Agency. Two independents, five Republicans and 46 Democrats voted to let the EPA proceed.

EPA issued the Utility MACT rule in December 2011 in response to a court-ordered deadline to which EPA agreed in a settlement with environmental and health advocacy groups in American Nurses Association v. Jackson. The rule does not apply to natural gas-fired power plants unless the gas is produced by gasifying coal or oil.

The rule limits the amount of not only mercury, but also arsenic, chromium, dioxins, lead, formaldehyde and other substances that may be emitted from power plants and requires use of “maximum achievable control technology” or “MACT” to control such emissions at power plants larger than 25 megawatts in size that burn coal or oil. Although the rule offers some flexibility to utilities that need more than the three years that the Clean Air Act allows for installing the required air emissions control technology, power plants that use coal are expected to be particularly hard hit.

Senator Inhofe is the ranking Republican on the Senate Environment and Public Works Committee.

Congress is expected to take more “message” votes in the run up to the national elections in November as the two political parties try to make clear where they differ on policy. There are questions about the extent to which a new administration would be able to change course after November, since the mercury rule was issued under a court order.