Airborne lead is still a health problem, the U.S. Environmental Protection Agency (EPA) tells us. The secondary lead industry still has 21 smelters in the United States, according to the U.S. Geological Survey, so the secondary lead industry must rank first or second as a source or airborne lead, right? Wrong.
Secondary lead smelters are listed as sixth, contributing only 3.2 percent of the lead getting into the air, according to a set of EPA estimates. Ahead of secondary lead smelters in the ranking are iron and steel foundries (second), primary lead smelting (third), industrial/commercial/institutional boilers and process heaters (fourth) and hazardous waste incineration (fifth).
First place Piston-engine airplanes using leaded aviation gas (avgas) to power propellers. But aren't corporate airplanes all jet propelled now? Think Walter Matthau's day job when he played a bank robber in Charley Varrick. Crop dusting. You don't hear much about that industry, but it does burn gasoline and it does have a National Agricultural Aviation Association.
"Avgas is commonly used in piston engines, which account for approximately 54.66 percent of agricultural aircraft," according to that trade group. "Although no specific regulations have been promulgated at this time, our organization remains committed to working with the EPA to reduce the burdensome effects regulations could have on our industry."
Looked at closely, much of environmental regulation is counterintuitive. And a surprising amount of it is sketchy.
The Institute of Scrap Recycling Industries is wrangling with a California agency over shredder fluff, the nonmetallic component left after grinding up vehicles. The state's Department of Toxic Substances Control wants to end the use of such residue in garbage landfills as an end-of-day cover, although a bill in the California legislature seeks to have a study panel examine the issue first. Part of the study's mandate would be to identify the constituents in auto shredder residue that could pose health and safety or environmental problems.
At various times lead, zinc, cadmium and polychlorinated biphenyls (PCBs) have been cited as risks. However, there's no authoritative analysis of fluff's ingredients, which can vary quite a bit among shredders and over time.
Linking pollutants and their consequences is rarely as straightforward as infectious disease. We're confident malaria is caused by protozoan parasites of the genus Plasmodium. Inanimate causes are trickier, and the EPA's public statements are carefully worded when smelters and die casters fall under scrutiny and face penalties that sometimes approach $100,000.
The science of lead poisoning is least ambiguous because the element was widely available for decades in paint and gasoline. Large numbers of people received middling doses and they were studied, so the EPA's boilerplate when it announces financial penalties for lead emissions is straightforward "Exposure of young children to lead can cause irreversible brain and central nervous system damage, causing impaired growth development, lower IQ levels and behavioral problems."
At secondary aluminum smelters, the substances of concern are closely related chemical groupings, dioxins and furans. In those press releases, EPA treads carefully. "There is evidence that dioxins may cause liver damage and probably cause cancer in humans, and furans may cause cancer in humans."
Falling in the middle of the certainty scale is the PCB issue "PCBs are persistent in the environment and are suspected carcinogens. In addition, exposure to PCBs can cause liver problems and skin rashes."
All three of the pollutants are among the 31 rated as priority concerns at EPA's hazardous waste office. The EPA also tracks 548 substances in its Integrated Risk Information System. And unveiled in March was EPA's Aggregated Computational Toxicology Resource database, with entries for "more than 500,000 man-made chemicals." With such a dizzying array of materials flitting across the radar screen, we have to hope the agency can choose its priorities wisely.
Since lead's recycling ratio is extremely high, and since PCBs are no longer intentionally introduced into products, the really tricky regulatory item among the three cited is the dioxin group. Those chemicals aren't produced for use, but they are an undesirable result of several processes, including the melting of aluminum scrap that has been in contact with grease.
Greenpeace published two polemics, 10 years apart, arguing for zero tolerance of the stuff. A 2004 book on dioxin was subtitled Truth and Lies About a Perfect Poison. On the other hand, the EPA has been criticized by a National Academy of Sciences (NAS) panel for erring in an alarmist direction.
All the players agree that there's very little reliable information available on the effect of low dioxin exposures. Almost any research strategy ends up being educated guesswork based on data for high human doses—workplace exposure or accidents—or on data from animal studies. The suspected consequences of low-dose dioxin include lymphoma and lung tumors.
Even the skeptical NAS task force had difficulty reaching its own consensus. Some members thought "carcinogenic to humans" was an acceptable label for dioxin, using the EPA's normal rulebook. Others didn't. Another split Would the EPA learn anything useful by trying to quantify the uncertainties over low dioxin doses?
The EPA convened a three-day seminar of about 60 outside experts early this year on how to respond to the NAS critique. A physician who spent several years in medical research looked through a summary of the proceedings and commented "There's no point in getting data if it's not going to change your management." His point Will further research affect any of the anti-pollution rules impacting aluminum smelters? Probably not.
The wrangling over the effects of dioxin on health actually goes back to the Vietnam War, when the chemical was used in Agent Orange and some other herbicides to eliminate jungle areas within which insurgents had been hiding.