The great hopes for reducing cancer by reducing environmental exposures to chemicals have not been realized because they were based on a wildly incorrect notion about the importance of environmental exposures in causing cancer. The notion arose from a misunderstanding of the word “environment” coupled with clear incentives to perpetuate and publicize the misunderstanding.
“Environment”
John Higginson, the first director of the World Health Organization’s International Agency for Research on Cancer, is credited with coining the expression that the environment causes upwards of 90 percent of all cancers As he used the word, “environment” included everything with which people come in contact, “Environment is what surrounds people–and impinges upon them.… the air you breathe, the culture you live in…the chemicals with which you come in contact.” [1] He explained that many people misunderstood the word “environment” to mean chemicals, and he underscored the strong incentive for some people and organizations to have it misunderstood in that way.
A lot of confusion has arisen…because most people…have used the word ‘environment’ purely to mean chemicals.…
The ecological movement, I suspect, found the extreme view convenient because of the fear of cancer. If they could possibly make people believe that cancer is going to result from pollution that would facilitate the cleaning up of the water, the air, whatever it was… People would love to be able to prove that cancer is due to the general environment or pollution. It would be so easy to say ‘let us regulate everything to zero exposure and we have no more cancer.’ The concept is so beautiful that it will overwhelm a mass of facts to the contrary. [2]
Higginson was right. The idea that environmental pollutants are the cause of much of human cancer is very attractive. In the first place, it explains the inexplicable. Although 25 percent of people in the United States will develop cancer at some time during their lives, and about 20 percent of all deaths are caused by cancer, the causes of most cancers remain unknown. Being told that the causes lurk in environmental chemicals provides an explanation for the occurrence of cancer. Secondly, and even more satisfyingly, if chemical causes can be identified and eliminated, cancer rates should fall.
The “Environment” and Cancer
The evidence that the environment is a significant cause of cancer was never strong, but scientific reviews of information about causes of cancer had little influence on public policy until 1981. In that year, Sir Richard Doll and Richard Peto published their encyclopedic analysis of the causes of cancer, which investigated the evidence for the widely discussed “cancer epidemic” and catalogued the causes of cancer in the United States. [3]
Doll and Peto documented that cancer deaths were increasing among elderly people who, because of reductions in deaths from infectious diseases, heart diseases, and accidents, lived to the advanced ages where cancer is common. [4] Even so, the percentages of elderly people who died from cancer were not increasing. When allowances were made for the increased number of cancer deaths expected in an aging population and for increases in lung cancers, the age‐adjusted death rate from all cancers had not changed over the four decades from 1933, when collection of national data began, through the 1970s, the latest years for which data were available when Doll and Peto did their research. There was no evidence for a surge in overall cancer rates.
During the four decades for which Doll and Peto had data, mortality from some cancers–especially pulmonary cancers–had increased, and mortality from other cancers–especially stomach cancers–had decreased. Increased rates of pulmonary cancers followed increases in smoking; reduced stomach cancer rates accompanied changes in food preservation that reduced the amounts of ingested natural toxic materials and of meats preserved by smoking and salting. Age‐adjusted mortality rates from cancers at other body sites remained nearly constant from the 30s through the mid‐70s.
More recently, Susan S. Devesa and her colleagues at the National Cancer Institute compared cancer rates in the United States in the 1975 through 1979 period to rates in 1987 through 1991. Cancer incidence rates increased 19 percent in men and 12 percent in women, with almost all the increases being accounted for by higher prostate cancer rates in men and higher breast and lung cancer rates in women. Devesa et al. concluded “Improved detection appears to account for most of the increases in breast cancer among women and prostate cancer among men. On the other hand, cigarette smoking is the major determinant of the rise in lung cancer among women.” [5]
Deaths from cancer increased less, three percent and six percent among men and women, respectively, between the late ‘70s and ‘80s. Those increases were “driven mostly by continuing increases in lung cancer mortality , while death rates for the majority of cancers were steady or declining.” [6] In fact, clear decreases in cancer mortality were apparent among both men and women under 55.
One conclusion from Devesa et al. is especially important to any discussion of environmental causes of cancer:
Increasing exposure to general environmental hazards seems unlikely to have had a major impact on the overall trends in cancer rates, in agreement with the conclusion reached in a recent investigation of mortality trends in England and Wales, although rising rates from certain tumors have been clearly influenced by changing exposures to tobacco smoking, HIV infection, and sunlight exposure. [7]
Reduced mortality rates among younger age groups usually presage reduced rates as they age. For that reason, it could be expected that the reduced cancer mortality in people under 55 in the study by Devesa et al. will accompany them as they age, and that cancer mortality for all ages will decrease.
In November of last year, Philip Cole and Brad Rodu of the University of Alabama in Birmingham published an analysis showing that overall death rates from cancer began to decrease in 1990 and that the rate of decrease is accelerating. [8] Better medical care has reduced mortality in people who develop cancer, and decreased smoking has reduced the number of people who develop lung cancer as well as fatal cancers at other body sites. In addition, Cole and Rodu state that reductions in exposures to carcinogenic substances in the workplace and reductions in alcohol consumption and exposures to sunlight have contributed to decreases in cancer mortality.
Cole and Rodu don’t mention “environmental chemicals” in their discussion of causes of cancer. There’s good reason. They have little to do with cancer. Smoking is the major culprit, and lung cancer rates have been declining since 1990 as a result of decreased smoking that began about 1965. For cancer at other sites, Cole and Rodu cite NCI analyses that show mortality rates from those cancers “been declining since at least the early 1970s.” [9]
Exposures Associated with Cancer
In their 1981 study, Doll and Peto concluded that “pollution,” their term for chemicals in the environment, was associated with about two percent of all cancers (see table 1). These results were far different from the conclusions that had been reached by people who equated the word “environment” with “chemicals,” [10] but Doll and Peto’s work conclusions have become accepted wisdom, and few people argue today that “cleaning up the environment” is going to make much difference in cancer rates.
EPA itself presented data about the minor importance of environmental exposures on cancer rates in its 1987 report Unfinished Business. EPA’s scientific and technical managers’ estimates of the numbers of cancers expected from environmental hazards agreed closely with Doll and Peto’s. EPA estimated that pollution caused 1 to 3 percent of cancer [11] compared to Doll and Peto’s estimates of 2 percent. Indeed, EPA and Doll and Peto’s estimates for all the causes of cancer that might be regulated agree, and they are all low (see table 1). [12] Subsequently, I calculated that if EPA’s estimates of cancer risks from environmental exposures were correct and if its regulatory programs were 100 percent successful in controlling those exposures, the agency could eliminate between 0.25 and 1.3 percent of all cancers. [13]
Table 1
Percentages of Cancer Deaths Attributed to Various Factors
Percentage of all cancer deaths
Source of estimate
Doll and EPAb Willettc Ames
Petoa et al.d
Factor or class of factors
Diet 35 (10–70)e — 32 (20–42) 20–40
Tobacco 30 (25–40) — - 35
Infection 10 (1->10)f — - -
Reproductive and sexual
behavior 7 (1–13) — - -
Occupation 4 (2–8) 1–4 — 5
Alcohol 3 (2–4) — - -
Geophysical factors
(natural radiation) 3 (2–4) 3–6 — -
Pollution 2 (<1–5) 1–3 — -
Food additives 1 (-5–2) — - -
Medicines and medical
procedures 1 (0.5–3) — - -
Industrial (consumer)
products <1 (<1–2) <1 — -
Unknown ?f — - -
__________
a. Richard Doll and Richard Peto, Journal of the National Cancer Institute 66 (1981):1191–1308.
b. Environmental Protection Agency, Unfinished Business (USEPA: Washington, DC, 1987); tabulated in Michael Gough, Environmental Science and Technology 23(1989):925–930.
c. Walter C. Willett, Environmental Health Perspectives 103 (1995) Supplement 8:165–170.
d. Bruce N. Ames, Lois Swirsky Gold, and Walter C. Willett, Proceedings of the National Academy of Sciences, USA 92 (1995):5258–5265.
e. The best estimate is presented, followed by the “range of acceptable estimates.”
f. “Very uncertain” according to Doll and Peto.
Cancer, the Environment, and Regulations
There are about 530,000 cancer deaths annually in the United States. According to EPA’s estimate, pollution causes 1 to 3 percent of cancers, or between 5,300 and 16,000 cancer deaths annually. According to my estimate, EPA regulation, if it works perfectly, can prevent between 0.25 and 1.3 percent of cancers, or between 1,300 and 7,000 cancer deaths. Environmental exposures account for only a tiny fraction of cancers, and EPA regulations, if perfect, can reduce cancer rates by no more than about 1 percent. Any good from such regulation may be offset because regulations of pesticides are likely to drive up food costs. Diets rich in fresh fruits and vegetables protects against cancer, [14] and pesticides, by lowering production costs and increasing storage and shelf life, make fruits and vegetables less expensive and more available.
EPA regulations are expensive when compared to regulations from other agencies. On average, EPA regulations cost fully 330‐times more to save a year of life than do Federal Aviation Administration regulations [15] (table 2). What’s more, most calculations of the effectiveness of EPA regulations are based on estimates of human risk extrapolated from the results of animal tests. Because of EPA’s risk estimation procedures, those estimates, uncertain as they are, are weighted to overestimate the benefits from regulations. In contrast, FAA’s estimates are based on analyses of real accidents involving real people.
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Table 2
Median Cost per Life‐Year Saved by Regulations from Federal Regulatory Agencies
Agency_______________________________Cost per Life‐Year Saved
Federal Aviation Administration $ 23,000
Consumer Product Safety Commission 68,000
National Highway Traffic Safety Administration 78,000
Occupational Safety and Health Administration 88,000
Environmental Protection Agency 7,600,000
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Source: Tammy O. Tengs, et al., Risk Analysis 15(1995):369–390.
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It’s well known that “wealthier is healthier;” that, on average, wealthier people live longer, healthier lives. Regulations cost money, and the money that is spent on them is not available to individuals for the purchase of better food, housing, transportation, schooling, medical care, and recreation, all of which can contribute to longer, healthier lives. In recent years, economists have estimated the impact of regulatory costs on life expectancy. Ralph Keeney estimates that every $7.5 million dollars spent to meet regulatory costs is associated with one premature death, [16] and Kip Viscusi estimates that every $50 million in regulatory costs is associated with one premature death. [17] Loud objections have been raised to these estimates, but I think that no one has argued that spending to meet regulation‐generated costs makes people healthier.
If Keeney’s estimate that $7.5 million in regulatory costs are associated with one premature death is correct, every life‐year purchased by $7.6 million in EPA regulatory costs is offset by one premature death. According to Viscusi’s estimate that associates one premature death with $50 million in regulatory costs, EPA regulations that save about seven years of life are associated with one premature death. The benefits of EPA’s regulations are almost certainly overestimated, meaning that fewer years of life are saved as a result of EPA’s regulations.
Fundamental to rethinking EPA’s role in cancer prevention is a willingness to address science and policy separately and appropriately. EPA laces its documents with claims that its policies are “science‐based” and incorporate the “best science.” Both claims have enormous political advantages for EPA. Either claim moves EPA activities from the policy arena, where Congress and other non‐technically trained organizations and citizens have a voice, and sets them up as issues to be left to “technical” or “science‐based” organizations like EPA.
In fact, a set of assumptions, sometimes called “science policy choices,” is central to EPA’s decisionmaking. Most of the choices are made on the basis of “prudence” or “necessity to protect human health and the environment.” Those are certainly worthy goals; they are not technical decisions. Absent from the choices are consideration of whether regulations actually cost lives or whether the money spent on EPA regulations would be better spent elsewhere. Those policy decisions should not be reserved to EPA.
What we know now is far different from what was “known” 27 years ago. Does the knowledge that the environment plays little role in cancer make any difference to EPA and its supporters in their drive to reduce cancer by reducing exposures to chemicals in the environment? No. Can we expect that such knowledge will ever make a difference? Yes, if Congress reconsiders EPA’s mandate and investigates the underpinnings for expectations that regulation of environmental carcinogens will improve public health.
Conclusions
There is no cancer epidemic. Cancer mortality from all cancers other than lung cancers has been dropping since the early 1970s, and lung cancer mortality began dropping in 1990. The contribution of environmental exposures to cancer is small–two percent or less–and regulation of those exposures can reduce cancer mortality by no more than one percent. Some of that reduction, even if realized, might be offset by increased food prices that would decrease consumption of fresh fruits and vegetables that are known to protect against cancer.
The already measurable successes in the fight against cancer, brought about by better treatment coupled with reduced smoking, drinking, and exposures to workplace carcinogens and to sunlight, point the way to continuing progress. In addition, better understanding of the role of diet in cancer prevention and of the cellular and molecular mechanisms of carcinogens are like to have major payoffs. To pursue environmental causes in the expectation of having any detectable effects on cancer rates is to chase a will-o’-the-wisp.
Notes
[1] “Cancer and Environment: Higginson Speaks Out,” Science 205 (1979): 1363–1366, at p. 1363.
[2] “Cancer and Environment,” at pp. 1363–1364.
[3] Richard Doll and Richard Peto, “The Causes of Cancer: Quantitative Estimates of Avoidable Risks of Cancer in the United States Today,” Journal of the National Cancer Institute 66 (1981):1193–1308.
[4] Larry Kessler, a statistician at the Food and Drug Administration, appeared on the August 20, 1996, broadcast of NBC’s Dateline. He stated that “The greatest single risk is aging.”
[5] Susan S. Devesa, William J. Blot, B.J. Stone, et al, “Recent Cancer Trends in the United States,” Journal of the National Cancer Institute 87(1995):175–182.
[6] Devesa et al. 1995 at p. 175.
[7] Devesa et al. 1995 at p. 181.
[8] Philip Cole and Brad Rodu, “Declining Cancer Mortality in the United States,” Cancer 78(1996): 2045–2048.
[9] Cole and Rodu 1996 at p. 2046.
[10] See “Cancer and Environment: Higginson Speaks Out.”
[11] U.S. Environmental Protection Agency, Unfinished Business. A Comparative Assessment of Environmental Problems. Appendix I: Report of the Cancer Risk Work Group. (USEPA: Washington, DC, February 1987).
[12] Michael Gough, “Estimating Cancer Mortality. Epidemiological and Toxicological Methods Produce Similar Assessments, Environmental Science and Technology 23 (1989):925–930.
[13] Michael Gough, “How Much Cancer Can EPA Regulate Away?” Risk Analysis 10 (1990):1–6.
[14] Bruce N. Ames and Lois S. Gold, “The Causes and Prevention of Cancer: The Role of Environment,” in The True State of the Planet, ed. Ronald Bailey (New York: Free Press, 1995; Bruce N. Ames, Lois S. Gold, and Walter W. Willett, “The Causes and Prevention of Cancer,” Proceedings of the National Academy of Sciences 92 (1995):5258–5265; National Research Council, Carcinogens and Anticarcinogens in the Human Diet (Washington: National Academy Press, 1996), pp. 336–337; Walter C. Willett, “Diet, Nutrition, and Avoidable Cancer,” Environmental Health Perspectives 103 (1995) Supplement 8:165–170.
[15] Tammy O. Tengs, et al. “Five‐hundred Life‐saving Interventions and Their Cost Effectiveness. Risk Analysis 15 (1995):369–390.
[16] Ralph L. Keeney, “Mortality Risks Induced by Economic Expenditures,” Risk Analysis 10 (1990): 147–159.
[17] W. Kip Viscusi, “Mortality Effects of Regulatory Costs and Policy Evaluation Criteria,” RAND Journal of Economics 25 (1994):94–109.