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
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
"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
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
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
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
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
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
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
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.