A Little Learning About Lead
When public laws are based on scientific research, the research had better be adequate---or the law adaptable. Members of the city council in Aspen, Colorado, could testify to that; too little learning about lead is giving them big problems with the U.S. Environmental Protection Agency.
Aspen's problems began in 1981. A graduate student from Colorado State University performed some routine tests on the soil at Smuggler Mobile Home Park, a court northwest of the town with some 80 relatively immobile trailers in permanent residence. He hoped to help the residents improve their vegetable gardens, but what he found made gardening seem downright unhealthy. In and near Smuggler Park, soil lead levels were impressively high.
The student was not surprised. Two old silver mines lay close to Smuggler Park, and lead is a common by-product of such mining. But the numbers looked bad. In most parts of the nation, the EPA accepts 500 parts per million of lead in soil. Pragmatically, old mining areas (like much of Colorado) are considered safe enough with 1000 ppm. At Smuggler Park, some samples exceeded 20,000 ppm.
The county environmental health officer repeated the tests, coming up with the same results. He immediately warned Smuggler Park residents not to let children play in old mine tailings and not to eat any vegetables grown in the park. Then he took his concerns to the city council and the county commissioners.
The commissioners thought some remedial work, perhaps covering the lead-tainted ground with fresh soil, should be done before any more people moved into the contaminated area. A county engineer had heard of the Superfund program, and thought the Aspen site might qualify for federal assistance---not to be overlooked, since he estimated that remedial work could cost almost $750,000. Furthermore, under the Superfund provision for potentially responsible parties, or PRPs, the county might be able to recover some costs from the mining companies responsible for creating the mess in the first place. The commissioners wrote the EPA, asking for agency consideration.
In the decade since, Aspen has received more EPA consideration than it would like. The county has discovered it might be among the PRPs, liable for a share of a remediation bill the EPA recently estimated at better than $13 million.
Aspen has achieved rank number 929 on the Superfund list of 1200-odd sites to be cleaned, but no lead has been found in the water supply. The air has a lead particulate count lower than the national standard by about a factor of 10. Tests showed the lead contents in Smuggler Park residents' blood were lower than the national average, and well below a concentration that might affect health. In fact, they were about a sixth of the blood-lead levels found on average in the residents of Cincinnati.
The discrepancy between the dangerous-sounding amount of lead in the soil and its ap-parently undangerous effects comes from a property of lead and other metals not well appreciated when the Superfund law came into being. At Smuggler Park, the lead seems to be bound into a mineral matrix; in technical terms, it isn't bioavailable.
In practical terms, the particles it forms are too large to lodge in lungs. If someone ate an unwashed vegetable pulled from the lead-laden soil, the lead particles would pass harmlessly through that person's system.
The hazards of lead come from smaller, unbound particles, such as those put out by smelters or automobile exhaust. Such particles are bioavailable, and can stick in lungs and digestive tracts. But research showing that different forms of lead have different health effects isn't reflected in the Superfund law.
The latest thinking is that Smuggler Park is dangerous only if the matrix is broken up, say by someone excavating for a garage--or by the EPA digging up and trucking away thousands of loads of lead-heavy soil, as is now planned. That's an action Aspen is fighting, with recent research on lead bioavailability as the town's best weapon.
