Colorado health officials have granted Climax Molybdenum a third extension of a “temporary” lifting of the state’s health limit for molybdenum pollution of a creek, allowing continued elevated discharges above Denver’s drinking water supplies.
The delay, commissioners said, will give time for Climax to resolve scientific uncertainty around how much molybdenum is too much for people.
Climax has been lobbying the CDPHE to relax the statewide limit for molybdenum pollution of waterways, which would ease the company’s wastewater-cleaning burden.
Molybdenum is used to harden steel and for petroleum-industry lubricants.
An existing water treatment plant below the mine removes many contaminants, though not molybdenum.
Denver Water officials and downstream communities concerned about the contamination — CDPHE officials have said they’re aware of molybdenum spikes at up to 3,000 ppb – accepted giving Climax more time with the understanding that Climax would work to reduce the pollution.
“During the time the temporary modification is in place, additional independent analyses of the recently completed studies on molybdenum’s impact on human and animal health will proceed, and we look forward to discussing their conclusions with our stakeholders,” Kinneberg said.
The EPA hasn’t set a drinking-water regulation for molybdenum.
The Agency for Toxic Substances and Disease Registry, or ATSDR, has determined that ingesting no more than 45 micrograms of molybdenum a day is OK for adults but that most Americans ingest 76 to 109 micrograms.
Long-term exposure of rats and mice to molybdenum dust has been shown to cause damage to the nasal cavity and lungs.