Doe Run scrutinized for lead levels

Fresh air is a rare indulgence for kids in Herculaneum, Mo., these days. On the advice of health officials, street play is discouraged and most parks are off-limits until further notice. Parents may be too busy following state guidelines to mop the lead dust off their floors and walls to take their children to the only park deemed safe.

The state issued these extraordinary recommendations after examining the results of blood samples taken from 935 of 2,800 residents living in the vicinity of the Herculaneum lead smelter, owned by Doe Run Resources. The samples showed that 28% of children under the age of six living in the town had elevated blood-lead levels. For those living within one mile of the smelter, the number rose to 45%.

The mean blood-lead level in the United States is about 2 micrograms per decilitre. Elevated levels, those above 10 micrograms lead per decilitre, have been linked to learning disabilities, decreased growth and hyperactivity. Direct human exposure occurs through inhalation of particulate lead and ingestion of contaminated food, water and dust.

The latest results have prompted the Missouri health department to declare the Herculaneum smelter an “urgent” public health hazard, even though children in the town have tested positive for elevated lead levels ever since blood testing began more than 25 years ago.

But until the latest sampling program, in 2001, lead levels had been on a steady decline. The recent results have been a public relations disaster for Doe Run, triggering renewed scrutiny of the century-old smelter by the media and environmental groups. The company did not return phone calls.

To make a difficult situation worse, Doe Run is a financial basket case. In March, the company missed $15-million interest payment on a $305-million bond debt. Doe Run has since restructured its debt, but it remains vulnerable to lead prices, which recently dipped below US21 per lb., a 75-year low in real dollar terms.

The Herculaneum primary smelter, on the Mississippi River just south of St. Louis, is the largest lead smelter in the country. It was built in 1892 to serve the mines and mills of the ore-rich Viburnum trend of Mississippi-Valley type (MVT) lead-zinc deposits and has been in continuous operation ever since. Doe Run, the world’s largest primary lead producer, is owned by Renco Group, a holding company for a diverse group of businesses, including the manufacturer of the Humvee, the all-terrain vehicle used by the military, and the Hummer, its civilian counterpart.

Doe Run has been at war with state and federal regulators over contamination from the smelter for years. The smelter has been in non-compliance with air quality standards since at least 1990, when the Environmental Protection Agency (EPA) tightened the standards under the Clean Air Act. Soil contamination of up to 12,800 parts per million is also an ongoing concern. But it wasn’t until recently that the three parties were able to agree on what to do about the mess.

At the end of 2000, Doe Run and Superfund negotiated a 92-page administrative order of consent (AOC) that requires the company to clean up the air, soil and the water in the vicinity of the smelter. The AOC is Doe Run’s most comprehensive agreement with the government to date and includes new controls on air emissions, remediation of lead-contaminated residential yards, and investigation and stabilization of a contaminated slag pile in the Mississippi River flood plain. Doe Run has also agreed to buy out 160 lead-contaminated homes at the price that they would have sold for before increased news coverage of the contamination lowered property values.

Administrative order

Superfund, the federal program established in 1980 to locate, investigate and clean-up the worst hazardous waste sites in the U.S., identified the site as a problem several years ago. But regulators preferred to negotiate a deal with Doe Run rather than issue an immediate edict for cleanup that could be appealed by the company and held up for years.

“Superfund started really looking at the site in the 1990s, but it took several years to negotiate the administrative order,” says Karen Cass, the community relations officer for the Missouri Department of Natural Resources, Superfund division. “We wanted an AO on consent, and that takes a lot longer because the company has to agree to the terms.”

Soil acts as a sink in which lead can have a half-life of several centuries. According to Cass, virtually every property lying between the smelter and a highway roughly one mile away is contaminated with lead above 400 ppm, the level at which the EPA insists on cleanup. Some contain more than 2,500 ppm lead, compared with an average concentration of about 16 ppm in the earth’s crust. The EPA hasn’t even begun testing the soil on the other side of the highway that marks the informal border of the town.

By presstime, Doe Run had completed the first phase of its residence cleanup program by replacing the soil and lawns and cleaning the interiors of 63 high-priority homes near the smelter that have children under the age of six. The second phase of the program, which involves another 21 homes, is under way. Doe Run is also spending roughly US$12 million to reduce air emissions from the smelter.

But even though Doe Run has paved the road to the smelter and says it is cleaning haul roads daily and washing its concentrate trucks, fugitive dust from the site remains a problem.

“There are certain things that they are ahead of schedule on, like the yard cleanups and the new air emission controls,” says Cass. “But the concentrate trucks going through town are contaminating the roads over and over, and a lot of concentrate dust is still blowing around on [the smelter] property. One of our major concerns is the issue of re-contamination from the combination of air emissions and fugitive dust.”

Superfund will add the site to its National Priority list for cleanup if Doe Run goes bankrupt, she says.

Although cleaner technologies are available, Herculaneum, like most lead smelters, uses a conventional sinter and blast furnace to treat lead concentrate. First, most of the sulphur is removed from the concentrate by roasting in a sinter machine. The resulting gases are stripped of dust and other impurities, then converted to sulphuric acid. The cakes of sinter are crushed and fed to the blast furnace.

Chemical reactions within the blast furnace produce molten lead bullion (including metallic impurities such as copper and nickel), which is then cooled. As the metal impurities begin to freeze, they form a layer at the surface called “dross,” which is skimmed off and melted in a separate furnace. The remaining lead is pumped to a refinery.

Ventilation

The process allows plenty of opportunity for hazardous dust and fumes to escape, especially during the sintering stage. Companies must use extensive exhaust ventilation systems and clean lead-laden exhaust gases before they release them to the atmosphere.

There are several direct processing methods, including the QSL and Kivcet processes, that bypass the dirty sintering stage and avoid the largest environmental problem: dust. In 1997, the company now known as Teck Cominco replaced its old lead sinter and blast furnace at Trail, B.C., with a new smelter based on the Kivcet process, developed in Russia.

Using this process, concentrates and flux are roasted and smelted at the top of the smelting shaft. Dust formation is kept to minimum, and because the furnace operates at pressures below the surrounding pressures, fugitive dust emissions are low. At Trail, emissions of lead and other contaminants decreased by 68% to 96% between 1995 and 1999 as a result of the new smelting technique.

Rather than replace their technology, Doe Run has upgraded the existing smelter with better ventilation systems. But so far the results have been mediocre. Although levels of lead in ambient air dropped 21% in 2000, it was not until this year that the company was able to report that the smelter made it through a whole quarter in compliance with federal air re
gulations.