Debate over lead in air
Are lead levels in the air so low that the contaminant should no longer be a criteria pollutant?
When the U.S. EPA raised the possibility of removing lead from the list of six “criteria” air pollutants it regulates because ambient lead levels are no longer a problem in most parts of the country, the idea was widely ridiculed by environmental groups and a few key members of Congress as the action of an industry-friendly administration. Such a simplistic condemnation misses the point, according to experts contacted by ES&T, who say that delisting lead as a criteria pollutant fits with the letter of the Clean Air Act (CAA), but as a practical matter doesn’t protect public health.
The option to delist lead was mentioned in a December 5, 2006, draft agency staff paper developed as part of a review of the criteria standard. The CAA requires EPA to review and, if needed, update the six criteria pollutants every 5 years, but the agency often misses these targets.
The current criteria standard, 1.5 micrograms per cubic meter (µg/m3) of air averaged over a 3-month period, was set in 1978 when public health officials thought that lead was much less harmful. A partial EPA review in 1990 suggested that the standard could go as low as 0.5 µg/m3 averaged over one month, but the agency never revised the standard.
The new leaders of two congressional committees that oversee EPA’s activities, Rep. Henry Waxman (D-CA), and Sen. Barbara Boxer (D-CA), immediately denounced the delisting option and cited lead’s well-known effects on the brain development of young children.
The draft paper comes just months after a scientific summary by EPA advisers concluded that no safe human level for lead exposure exists. The summary, endorsed by EPA’s Clean Air Science Advisory Committee (CASAC), didn’t offer any regulatory options.
Current levels of atmospheric lead in most parts of the country are very low, says Rogene Henderson, CASAC’s chairperson a senior scientist at the Lovelace Respiratory Research Institute in Albuquerque, N.M. “Air is just not a major source of lead in most parts of the country,” she says.
Yet public-health scientists familiar with the situation are divided about the issue. Some say that the “no safe level” conclusion of the CASAC review requires a new much tighter criteria standard for lead. Then ambient levels should be compared with that new standard, and if warranted, EPA can declare victory over airborne lead emissions.
Others support EPA’s delisting suggestion, saying that it may well be time to stop worrying about the very low levels of lead in the air over most parts of the country and instead focus on the high lead levels in the air around some industrial sites, such as lead smelters and battery recyclers. Currently lead is controlled as a criteria pollutant and as a Hazardous Air Pollutant (HAP).
Former CASAC chair Mort Lippmann, a New York University Medical Center professor of environmental medicine, endorses delisting of lead and tightening the HAPs emissions standard that would affect individual sources. “With lead long out of gasoline, it is now a classic point-source pollutant, and it should have a stringent emission standard,” he says.
But delisting lead as a criteria pollutant would actually wind up relaxing standards for smelters and other point sources, says Johns Hopkins epidemiologist Lynn Goldman, a former EPA assistant administrator.
HAPs, or air toxics, are regulated on the basis of available technology and cost considerations. The CAA allows the HAP standards to be linked to health effects through a “residual risk assessment”, but EPA has moved very slowly on these assessments in the past, so any suggestion that EPA would perform a residual risk assessment for lead is an empty promise, Goldman observes.
At the same time, the national criteria standard for lead is tougher than the HAP, “because they are designed to protect the health of sensitive populations,” says Goldman. If EPA removes lead from the criteria list, protection from lead exposure also will be weakened, particularly for individuals living near point sources such as smelters and battery recycling plants, she says.
CASAC’s Henderson and EPA spokesperson John Millett agree that lead emissions from smelters are a problem, but lead from smelters is already regulated as a HAP. The only primary lead smelter in the U.S. is in Herculaneum, Mo., about 30 miles south of St. Louis. Last year it emitted 25 tons of lead and met its HAP emissions limit according to EPA. Yet Herculaneum is one of two areas of the country that regularly fails to meet federal criteria lead standards. In 2002, 28% of children in the town had blood lead levels higher than the Centers for Disease Control and Prevention’s level of concern.
Maxine Lipeles, director of the Interdisciplinary Environmental Clinic at Washington University in St. Louis says that delisting lead as a criteria pollutant will worsen the situation in the town because the smelter would only have to meet the HAP rule. Missouri Department of Natural Resources environmental engineer John Rustige also supports the retention of lead as a criteria pollutant for practical reasons. “The HAP approach really only works for new permits. It’s not effective for existing facilities,” he says.
