From:
http://www.reason.com/rb/rb030701.html
March 7, 2001
What Cancer Epidemic?
By Ronald Bailey
Ever since the publication of Rachel Carson's Silent Spring in 1962, one of
the staples of environmentalist dogma has been that industrial chemicals and
pesticides are causing an epidemic of human cancers. "What...is driving the
modern cancer epidemic?" asks environmental activist Samuel Epstein in the
November 2001 issue of Tikkun. "Study after study points to the role of
runaway industrial technologies… producing a dizzying array of synthetic
chemicals that have never been screened for human health effects."
Worldwatch Institute founder Lester Brown concurs, noting, "Every human
being harbors in his or her body about 500 synthetic chemicals that were
nonexistent before 1920."
''Cancer is reaching epidemic proportions and we need to identify the links
between the public health crisis and the environment,'' declared Priscilla
Rosenwald of the Pennsylvania Women's Health and Environment Network during
a breast cancer conference in 1997. Such claims are often accompanied by
pleas for massively expensive regulations that would require removing even
the smallest traces of synthetic chemicals from the environment.
But are we in the midst of a rising cancer epidemic? No, according to
Cancers Facts and Figures 2001, issued earlier this year by the American
Cancer Society (ACS).
"Overall cancer incidence and death rates have continued to decrease in men
and women since the early 1990s, and the decline in overall cancer mortality
has been greater in recent years," concludes the ACS report. The National
Cancer Institute (NCI) annual report for 2000 also found that "the number of
new cancer cases per 100,000 persons per year-for all cancers combined
declined on average 0.8 percent per year between 1990 and 1997." In fact,
the incidence of cancer has declined by 1.3 percent per year since 1992,
according to the NCI.
A lot of furor over cancer rates can be traced to the seemingly dramatic
increases in breast and prostate cancer during the 1980s. "The apparent
increases in the incidence of breast and prostate cancer are mostly due to
increased screening," according to Mary Beth Hill-Harmon, an epidemiologist
with the American Cancer Society. In other words, doctors got better at
detecting breast and prostate cancers earlier, so this artificially pumped
up their numbers temporarily.
For example, with the advent of the prostate specific antigen test (PSA
test), prostate cancer rates increased an astonishing 17.5 percent year
between 1988 and 1992. Since extensive PSA testing has uncovered a lot of
early-stage cancers, the rate of incidence fell by 10.3 percent per year
from 1992 through 1995, and has been flat since then.
Similarly breast cancer incidence rates jumped from 1 percent increases per
year between 1979 to 1982 to 4 percent increases per year between 1982 and
1987 (they've been largely constant since 1987). Again, the apparent
increases are a result of more vigorous mammography screening efforts.
So in recent years, actual cases of cancer are declining. How many people
die of the disease? In 2001, the ACS estimates that cancer will strike
1,280,000 Americans and that it will kill 553,400 people. Cancer is second
only to heart disease as a cause of death, accounting for 23.2 percent of
all U.S. deaths in 1998. However, overall cancer death rates also declined
by 0.6 percent per year between 1991 and 1995.
Breast cancer death rates dropped 2.2 percent per year between 1990 and
1997. Colon and rectal cancer death rates have been decreasing 1.8 percent
per year since 1984. Lung cancer death rates dropped among men by 1.7
percent per year between 1990 and 1997, and prostate cancer rates decreased
by 4.4 percent annually between 1994 and 1997. The five-year survival rate
for all cancers combined is now 60 percent. These improvements in cancer
death rates are largely a result of earlier detection (when the disease is
more easily treated) and the development of more effective therapies.
No rising cancer epidemic then. But perhaps the declines in cancer rates are
a result of regulatory efforts to rein in industrial chemicals? That's
unlikely, since very few cancers are caused by synthetic chemicals in the
first place. Sir Richard Doll, head of the Clinical Trial Service &
Epidemiological Studies Unit in Britain, estimates that only 1 to 5 percent
of cancers can be attributed to pollution. The American Institute for Cancer
Research also concluded, "There is no convincing evidence that eating foods
containing trace amounts of chemicals such as fertilizers, pesticides,
herbicides and drugs used on farm animals changes cancer risk. Exposure to
all manufactured chemicals in air, water, soil and food is believed to cause
less than 1% of all cancers."
So what does cause cancer? According to Doll, smoking tobacco causes about
30 percent of cancer; diet--especially consumption of animal fat--is
responsible for between 20 percent and 50 percent; infections are
responsible for between 10 percent and 20 percent; and natural reproductive
hormones account for 10 percent to 20 percent. A good portion of the
decreases in both cancer incidence and death rates in the U.S. can be
attributed to sharp declines in the number of smokers.
That's all good news, of course, even if it does burst the bubbles of the
Lester Browns of the world and undercuts their demands for the removal of
trace amounts of synthetic chemicals from the environment.
Here's some bad news: While there is no epidemic of cancer, further
reductions in the cancer incidence rate in the U.S. depend upon getting
people to improve their diets and to stop smoking. That's no easy task, for
sure.
Ronald Bailey (rbailey@reason.com) is REASON's science correspondent.
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