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#120 - Niosh Issues Cancer Alert For Diesel Exhaust Fumes, 13-Mar-1989

One reason why people often oppose a new facility is increased truck
traffic. Trucks are big and noisy and subject to accidents, and when
accidents occur involving trucks, there's a high likelihood of

However, the federal government has recently concluded officially that
there is another good reason to be concerned about increased truck
traffic in your neighborhood: five separate studies in the last 3 years
have shown that diesel exhaust certainly causes cancer in laboratory
animals, and two studies of railroad workers show that it causes cancer
in humans as well. As a result of this determination, the National
Institute for Occupational Safety and Health (NIOSH) has issued a
EXHAUST, offering this recommendation: "As prudent public health
policy, employers should assess the conditions under which workers may
be exposed to diesel exhaust and reduce exposures to the lowest
feasible limits." Citizens may reasonably ask: if NIOSH believes
workers should not be exposed to diesel exhaust because of the cancer
hazard, can health officials in other parts of government believe that
the general public should continue to be exposed to diesel exhaust?
Taken in this light, risk assessments that discuss only the traffic
hazards associated with a facility are missing the major point: diesel
trucks can evidently kill innocent people even if no traffic accidents

Diesel engines are more efficient than gasoline engines; they produce
more horsepower per gallon of fuel, and they use a less-refined (thus
cheaper and more plentiful) fuel. When diesel fuel burns in an engine's
combustion chamber, the resulting exhaust contains gases and particles
(soot). The gases include nitric oxide, nitrogen dioxide, oxides of
sulfur, and hydrocarbons (e.g., ethylene, formaldehyde, methane,
benzene, phenol, 1,3 butadiene, acrolein, and polynuclear aromatic
hydrocarbons [PAHs], several of which are known carcinogens). Of the
particles in diesel exhaust, 95% are less than 1 micron in diameter and
thus they are respirable, which is to say they are easily taken into
the deepest portions of the human lung where they may lodge forever.
The core of each particle is made up of pure carbon, but as many as
18,000 different chemicals from the gaseous portion of the exhaust may
be adsorbed (attached) onto the carbon core, and thus diesel exhaust
can carry a whole host of exotic, toxic and carcinogenic chemicals into
the deepest portions of your lung-down in the region where the transfer
of gas occurs to put oxygen into your blood stream and to take carbon
dioxide out.

As recently as 1986, NIOSH concluded that diesel exhaust did not cause
cancer in laboratory animals. However, in the period 1986-1988, five
long-term animal studies, and two epidemiologic studies of humans, all
concluded that exposure to diesel exhaust causes lung cancer. As a
result, NIOSH reversed itself and in August, 1988, issued a special
"current intelligence bulletin" to get the word out that diesel fumes
are dangerous. NIOSH estimates that 1.35 million American workers are
routinely exposed to diesel exhausts.

Cincinnati, OH: Division of Standards Development and Technology
Transfer, NIOSH, Robert A. Taft Laboratories [4676 Columbia Parkway,
Cincinnati, OH 45226], August, 1988; phone (513) 5338287. It's 30 pages
and free.

--Peter Montague



Traditionally, people concerned about the toxicity of chemicals have
mainly worried about the mouth and lungs as a means of entry into the
human body. Now new evidence suggests that absorption through the skin
may be an important way for some chemicals to enter the body. In
addition, the skin of babies may allow more toxics to pass through it
than the skin of older humans.

Researchers at the National Institute of Environmental Health Sciences
studied the absorption of dioxins and furans in mice and rats. They
discovered several new aspects of chemical absorption by the skin: (1)
the skin presents a more effective barrier against some chemicals than
against others; (2) mice absorb a greater percent of dioxin when lower
doses are administered than when higher doses are administered; (3)
young adult rats absorbed a greater percentage of the administered dose
than did middle-aged rats.

In the past, the theory has been that the skin (which has a total area
of 1.8 square meters in the adult human) has served as a passive
barrier to chemicals. Now it is apparent that the skin is very active
in metabolizing (biologically altering) chemicals and that these
metabolic processes affect the way the body absorbs (or does not
absorb) a particular chemical. Sweat glands, sebaceous glands (which
produce oils), and hair follicles can all contribute to the way
chemicals are absorbed through the skin.

Chemicals administered at low doses are more effectively absorbed
through the skin than are chemicals administered at high doses. Mice
receiving 0.3 micrograms of dioxin per kilogram of body weight absorbed
40% of the dose; mice receiving 32 to 320 micrograms of dioxin per
kilogram of body weight absorbed less than 20% of the dose. This may be
important for human exposures, which usually occur at low doses over
long periods rather than in high doses over short periods.

Three month old rats (young adults) absorbed 16% of dioxin applied to
their skin; nine-month-old rats (middle-aged) absorbed less than 5% of
a similar dose.

Linda Birnbaum, who directed the research, says that her work shows
that acute toxicity from skin exposure to dioxins and furans is
"unlikely." Chronic (longterm) toxicity is a different matter: That's
where "you're going to have the potential to build up a body burden" of
the toxic chemicals, she says. Her work with young rats also concerns
her because there is evidence that the skin of human babies is much
more permeable than skin of adults.

The importance of this work for grass roots activists seems to be this:
if someone is going to expose your community to small amounts of
dioxins and furans for a long time, ask them to please consider
absorption through the skin, and especially so in the case of babies
and children. Any risk assessments that have been done without
considering skin absorption should be redone in light of the new

Get: David Brewster and others, "Comparative Dermal Absorption of
2,3,7,8 Tetrachlorodibenzo-p-dioxin and Three Polychlorinated
Dibenzofurans." TOXICOLOGY AND APPLIED PHARMACOLOGY, Vol. 97 (January,
1989), pgs. 156-166. Reprints are free from: Linda S. Birnbaum,
Systemic Toxicology Branch, National Institute of Environmental Health
Sciences, Research Triangle, North Carolina 27709; phone (919) 541-
3212. Ask Ms. Birnbaum for a copy of her unpublished paper on
absorption of dioxins by young rats, which she presented at a meeting
of the Society of Toxicology in Atlanta, GA, the week of Feb. 27, 1989.

--Peter Montague


Descriptor terms: fine particles; nitrogen dioxide; nitrogen oxides;
sulfur oxides; hydrocarbons; pahs; diesel; air pollution; trucks;
transportation; studies; warnings; occupational safety and health;
cancer; health effects; niosh; cancer; traffic; emissions; lung; health
effects; dioxin; skin; infants; age; studies;