Two years ago, in 1997, the International Agency for Research on
Cancer (IARC) formally concluded that dioxin causes cancer in
humans. IARC is a division of the World Health Organization
(WHO) and its recommendations carry considerable weight in the
world of public health policy.
Dioxin is the name of a family of 219 toxic chemicals, many of
them created as unwanted byproducts of numerous industrial
processes: incineration of municipal solid waste, hazardous waste
and medical waste; the smelting of metals; the manufacture of
chlorine-bleached paper; and the production of many pesticides
and other toxic chemicals. Basically, any time you have high
temperatures and the presence of chlorine-containing chemicals,
you have conditions that can spawn dioxins.
Over the years, many studies of laboratory animals have shown
that dioxins can cause many different kinds of cancer. However,
in reaching its 1997 conclusion, IARC relied on studies of
humans, specifically, four studies of workers exposed to high
levels of dioxin on the job. The four studies revealed a
remarkably consistent effect from dioxin exposure: a 40%
increased chance of dying from cancer. In all four studies, the
effect was highly statistically significant.
In three of the four studies, data for estimating dioxin
exposures was available in 1997. Using the available exposure
data, the authors of the three studies were able to observe a
clear "dose response relationship" -- as the level of dioxin
exposure increased, so did the chances of dying of cancer. Seeing
a "dose response relationship" gives researchers more confidence
that the relationship they have observed (in this case, between
dioxin exposure and cancer) is real.
Now information about dioxin exposures among the fourth group of
workers has become available, and a dose-response relationship
can be seen in those workers as well. The more dioxin they
were exposed to on the job, the greater their chances of dying of
This fourth group was the largest of them all -- 5132 workers at
12 U.S. industrial plants where they were exposed to dioxin over
many years. Researchers at the U.S. National Institute for
Occupational Safety and Health (NIOSH) were able to find job
histories for 69% of the 5132 workers and thus could categorize
them into seven groups according to their dioxin exposures.
The new information appears in the May 5 issue of the JOURNAL OF
THE NATIONAL CANCER INSTITUTE. In their report, the NIOSH
researchers explain that they saw a 13% increased chance of dying
of cancer among the 5132 workers, compared to an unexposed group.
Among the highest two exposure groups, they observed a 60%
increased chance of dying of cancer.
In sum, we now have four separate studies of groups of humans who
have been exposed to dioxin and who are dying disproportionately
from cancers. These studies provide support for many previous
studies of laboratory animals showing that dioxin causes various
Does this close the book on dioxin and cancer? Unfortunately, it
Every group of humans who have been exposed to high levels of
dioxins has now been studied. There aren't any other groups to
study. Therefore, the data that are available now are probably
the only human data we will ever have. (Of course as time passes
these same groups will be studied further, but the results are
not likely to change dramatically.)
With today's data, it is still possible to reach conclusions that
are 180 degrees out of synch with each other. In an editorial in
the JOURNAL OF THE NATIONAL CANCER INSTITUTE May 5, Dr. Robert N.
Hoover of the U.S. National Cancer Institute wrote, "My belief,
based on the current weight of the evidence, is that TCDD [the
most potent dioxin] should be considered a human carcinogen."
This is precisely what the World Health Organization concluded
two years ago.
In contrast, when the British medical journal LANCET ran a news
story reporting the latest dioxin findings from the JOURNAL OF
THE NATIONAL CANCER INSTITUTE, they quoted Michael Kamrin, a
toxicologist from Michigan State University (East Lansing, Mich.
USA) who said the dioxin data is "unconvincing and
epidemiologically weak... These data don't suggest to me that
there's any health risk from dioxin [TCDD]. I didn't think so
before, and I don't think so now," Kamrin told the LANCET.
So the question is, how should ordinary people react to dioxin?
When we learn that we and our children are breathing dioxins
created by a medical waste incinerator, or a garbage incinerator,
or a cement kiln burning hazardous waste, what should we think?
Should we accept the opinion of Robert Hoover from the National
Cancer Institute that dioxin is probably a cause of human
cancers? Or should we accept the words of Michael Kamrin at
Michigan State who says there isn't any health risk from dioxin?
Experts can always disagree, but citizens must make choices in
the best interests of themselves and their families.
It seems clear that science cannot solve this kind of dilemma.
There has never been a chemical studied more thoroughly than
dioxin. For the past decade the U.S. government has been
conducting a detailed analysis of many hundreds of previous
studies of the health effects of dioxins (in animals and humans).
Furthermore, the government has spent millions of dollars
conducting new studies of dioxin's effects on humans (for
example, the NIOSH study, discussed above) and animals. In
addition, the Chemical Manufacturers Association and the Chlorine
Chemistry Council have spent substantial sums of money hiring
their own brand of scientist to try to tilt the balance in the
direction of "dioxin is no problem." (As you might imagine, there
are huge sums of money riding on the outcome of the dioxin
For most chemicals, we can probably never expect to get data as
good as the data we have now for dioxin. Given limited funds for
study, and given that there are 70,000 chemicals now in use and
1000 new ones added each year, we cannot realistically expect
anything like "thorough" data on the health effects of any
particular toxic chemical.
Therefore, how should we, the public, react to dioxin or any
other toxic chemical? There are two basic ways of approaching
such a question -- risk assessment or precaution.
Risk assessment asks the question, How much damage are we willing
to tolerate from dioxin exposure? Risk assessors usually answer
this question by saying that it is "acceptable" to kill one in
every million people exposed to dioxin. (Sometimes they give a
different answer, saying it is OK to kill as many as one in every
10,000 people exposed to chemical A or chemical B, but usually
their answer is that one-in-a-million is the acceptable kill
Now let us remove our rose-colored glasses for just a moment and
be blunt. You rarely find a risk assessor who will say so, but
the one-in-a-million formula is, at base, a prescription for
legalized murder. The dead person is selected at random and is
killed anonymously. But it is still a premeditated, planned
death. If "risk assessment science" improved to the point where
the victim's identity were known, then everyone would agree that
a murder had been committed.
Once the community of risk assessors has accepted that it is OK
to kill one-in-a-million citizens by exposing them to dioxin (or
some other toxicant du jour), then the mathematicians and
toxicologists go to work and develop a formula that says "exactly
this much dioxin can be emitted into the community, and no more,
if we are to abide by the one-in-a-million limit of 'acceptable
risk.'" Then it is up to the engineers to design a machine that
will emit just the "acceptable" amount of dioxin or other
toxicant and no more. And then the government regulators ratify
and enforce the engineer's limit. That is the sum and substance
of the "risk assessment" approach to controlling toxic exposures,
from dioxin or from any other deadly agent.
A different way to view the problem is to ask, How can we avoid
dioxin exposures and so avoid the possibility of killing people
with dioxin? This is the approach embodied in the "principle of
precautionary action." The precautionary principle says,
"When an activity raises threats of harm to human health or the
environment, precautionary measures should be taken even if some
cause and effect relationships are not fully established
scientifically. In this context the proponent of an activity,
rather than the public, should bear the burden of proof. [See
"The process of applying the Precautionary Principle must be
open, informed and democratic and must include potentially
affected parties. It must also involve an examination of a full
range of alternatives, including no action."
A precautionary approach to dioxin would look at the available
(sometimes conflicting) evidence about dioxin and ask, "If we
think it is better to be safe than sorry, shouldn't we avoid
dioxin exposures when we can?" And then the search would begin
for alternative ways to avoid dioxin exposures. Shutting down
incinerators -- or, better yet, not ever building incinerators --
would be one feasible approach. There are numerous alternatives
to incineration, and a "better safe than sorry" strategy would
examine all of them.
Reducing our use of chlorine-containing chemicals would be a
second approach. There are few, if any, uses of chlorinated
chemicals that are essential and irreplaceable. Alternatives are
In sum, a precautionary approach would not ask "How many dioxin
deaths can we tolerate in our society?" -- instead, it would ask,
"How can our society avoid making dioxin?"
The risk assessment approach, which has been the "official"
approach in the U.S. for the past 25 years, excludes citizens for
the most part because they don't have the knowledge to calculate
the one-in-a-million kill ratio. Only the "risk experts" are able
to do that. In that sense, the risk assessment approach is
undemocratic and even anti-democratic. ab But when it comes
time to deciding whether an incinerator is the best way to handle
the community's garbage, people can get involved. They can ask
citizens in other communities how they are handling THEIR
garbage. They can sponsor public discussions in which various
groups (including waste companies) send representatives to tell
how they would handle the community's wastes. People can ask
about the sources of waste in their community and they can demand
a "clean production" approach to those sources. (See REHW #650,
#651.) Then people can discuss the pros and cons of what they
have heard and can make up their own minds about what's best.
Unlike risk assessment, the precautionary approach fosters
citizen participation and promotes democracy.
--Peter Montague (National Writers Union, UAW Local 1981/AFL-CIO)
 Douglas B. McGregor and others, "An IARC Evaluation of
Polychlorinated Dibenzo-P-dioxins and Polychlorinated
Dibenzofurans as Risk Factors in Human Carcinogenesis,"
ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 106, Supplement 2 (April
1998), pgs. 755-760.
 Robert N. Hoover, "Dioxin Dilemmas," JOURNAL OF THE NATIONAL
CANCER INSTITUTE Vol. 91, No. 9 (May 5, 1999), pgs. 745-746.
 Kyle Steenland and others, "Cancer, Heart Disease, and
Diabetes in Workers Exposed to
2,3,7,8-Tetrachlorodibenzo-p-dioxin," JOURNAL OF THE NATIONAL
CANCER INSTITUTE Vol. 91, No. 9 (May 5, 1999), pgs. 779-786.
 Marilynn Larkin, "Public-health message about dioxin remains
unclear," LANCET Vol. 353 (May 15, 1999), pg. 1681.
Descriptor terms: iarc; who; dioxin; carcinogens; risk
assessment; precautionary principle; clean production;