THE "CANCER-CAUSING CHEMICALS" SCARE

The dose makes the poison

The main rule in toxicology is that 'the dose makes the poison'. At some level, every chemical becomes toxic, but there are safe levels below that.

In contrast to that rule, a scientific consensus evolved in the 1970s that we should treat carcinogens differently, that we should assume that even low doses might cause cancer, even though we lacked the methods for measuring carcinogenic effects at low levels. In large part, this assumption was based on the idea that mutagens - chemicals that cause changes in DNA - are carcinogens and that the risk of mutations was directly related to the number of mutagens introduced into a cell. It was also assumed that: 1. only a small proportion of chemicals would have carcinogenic potential; 2. testing at a high dose would not produce a carcinogenic effect unique to the high dose; and 3. carcinogens were likely to be synthetic industrial chemicals. It is time to take account of information indicating that all three assumptions are wrong.

Laws and regulations directed at synthetic chemicals got a big push from the widely publicised 'cancer epidemic', which supposedly stemmed from exposures to those chemicals. In fact, there is not now and there never was a cancer epidemic, and cancer mortality, excluding lung cancer mortality, has declined by 19 percent since 1950. Lung cancer mortality began dropping around 1990 as a result of reduced smoking rates, and that trend is likely to continue. Regardless of the absence of evidence for a cancer epidemic, the 'epidemic' has left a long-lasting legacy - a regulatory focus on synthetic chemicals.

The average American eats about 2,000 mg of burnt material, which is produced in usual cooking practices, each day. That burnt material contains many rodent carcinogens and mutagens, swamping, again, the 0.09 mg of 200 synthetic chemicals, primarily synthetic pesticides, that are ingested each day and that are classified as rodent carcinogens.

The natural chemicals that are known rodent carcinogens in a single cup of coffee are about equal in weight to a year's worth of ingested synthetic pesticide residues that are rodent carcinogens. This is so, even though only three percent of the natural chemicals in roasted coffee have been adequately tested for carcinogenicity. This does not mean that coffee or natural pesticides are dangerous; rather, assumptions about high-dose animal cancer tests for assessing human risk at low doses need re-examination.

The real problem

Inadequate diets, with too few fruits and vegetables, are common. Fully 80 percent of children and adolescents (26) and 68 percent of adults do not eat the five servings of fruits and vegetables per day recommended by the US National Cancer Institute and the National Research Council. Publicity about hundreds of minor hypothetical risks, such as pesticide residues, can cause a loss of perspective about what is important. In a survey, half the US public did not name fruit and vegetable consumption as protective against cancer.

Laboratory studies of vitamin and mineral inadequacy associate such deficiencies with DNA damage, which indicates that the vitamin and mineral content of fruits and vegetables may explain the observed association between fruit and vegetable intake and cancer risk. Antioxidants such as vitamin C (whose dietary source is fruits and vegetables), vitamin E, and selenium protect against oxidative damage caused by normal metabolism, smoking, and inflammation.

Laboratory evidence ranging from likely to compelling indicates that deficiency of some vitamins and minerals - folic acid, vitamins B12, B6, C, and E, niacin, iron, and zinc - causes damage to DNA that mimics the damage caused by radiation. In the USA, the percentage of the population that consumes less than half the Recommended Daily Allowance (RDA) in the diet (that is, ignoring supplement use) for five of these eight vitamins or minerals is estimated to be: zinc (10 percent of women/men older than 50), iron (25 percent of menstruating women, and 5 percent of women over 50), vitamin C (25 percent of women/men), folate (50 percent of women; 25 percent of men), vitamin B6 (10 percent of women/men), vitamin B12 (10 percent of women; 5 percent of men).....

The strongest effect in clinical trials was for a protective effect of vitamin E against cancers of the prostate and colon. More well-done trials will increase the information about the usefulness of supplements in cancer prevention. In the meantime, it is clear that intake of adequate amounts of vitamins and minerals may have a major effect on health, and the costs and risks of a daily multivitamin/mineral pill are low. More research in this area, as well as efforts to improve diets, should be high priorities for public policy.

Damage by distraction: Regulating low hypothetical risks

Synthetic chemicals that mimic hormones - 'environmental estrogens' or 'endocrine disruptors' - arose as a major environmental issue in the 1990s. Environmental concerns have focused on exposures to estrogenic organochlorine residues (largely plastics and pesticides) that are tiny compared to the normal dietary intake of naturally occurring endocrine-active chemicals in fruits and vegetables. These low levels of human exposure to the synthetic chemicals seem toxicologically implausible as a significant cause of cancer or of reproductive abnormalities.

Recent epidemiological studies have found no association between organochlorine pesticides and breast cancer, including one in which DDT, DDE, dieldrin, and chlordane were measured in blood of women on Long Island. Synthetic hormone mimics have been proposed as a cause of declining sperm counts, even though it has not been shown that sperm counts are declining. An analysis of US data about sperm counts found distinct geographical differences, with the highest concentrations in New York City. When geographic differences were taken into account, there was no significant change in sperm counts for the past 50 years.

Some recent studies have compared estrogenic equivalents (EQ) of dietary intake of synthetic chemicals v phytoestrogens (estrogens of plant origin) in the normal diet, by considering both the amounts consumed by humans and estrogenic potency. Results support the idea that synthetic residues are orders of magnitude lower in EQ and are generally weaker in potency. Scientists using a series of in vitro assays calculated the EQs in 200 ml of Cabernet Sauvignon wine and the EQs from average daily intake of organochlorine pesticides. EQs in a single glass of wine were about 1,000 times higher.

Conclusions

Because there is no risk-free world and resources are limited, society must set priorities based on cost-effectiveness in order to save the most lives. The EPA projected in 1991 that the cost to society of US environmental regulations in 1997 would be about US$140 billion per year (about 2.6 percent of gross national product). Most of this cost is borne by the private sector, which passes much of it along to consumers in higher prices.

Regulatory efforts to reduce low-level human exposures to synthetic chemicals because they are rodent carcinogens are expensive, can do nothing but reduce already minuscule chemical concentrations, and are unlikely to have any effect on cancer rates. Moreover, they distract from the major task of improving public health through increasing scientific understanding about how to prevent cancer, and increasing public understanding of how lifestyle influences health.

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THE LATEST "HOCKEY STICK" UPDATE FROM ROSS McKITRICK

See the original here for links. The original hockey-stick team now seem to be ignoring most of the data and hanging their whole case on a single sample of long-lived desert trees -- bristlecone pines. That what happens in one desert might not represent the whole climate of the earth is obvious to anyone who knows how great regional climate variations can be. Due to local effects, one place can be cooling while the other is warming and vice versa

There is a lot of material to wade through, and we appreciate that readers may be feeling somewhat buried by it all. Mann et al. are blogging away at realclimate.org, adding to the list of things experts need to consider. We would like to highlight the following points for those trying to keep up:

* While most attention is focusing on our GRL paper, since it is the more prominent journal, it is essential that people also read the Environment and Energy paper which rebuts (or 'pre-buts') a lot of the comments now issuing from the hockey team over at realclimate.

* We have prepared a pdf "backgrounder", available here. This provides a nontechnical overview of our work. See also BACKGROUND MATERIAL below for links to FAQs and a rebuttal of the responses made to our work.

* The argument that our work "doesn't matter" hinges on 2 points: (a) if MBH use 5 (instead of 2) PCs, they can salvage a hockey stick, and (b) there are many independent studies that also yield a hockey stick. Point (a) is treated in our Environment and Energy paper. The issue is robustness. If a low-order PC, representing less than 8% of the explained variance in a single regional proxy network, is going to be allowed to overturn the conclusion that would be indicated by the entire rest of the data set, why even include the rest of the data? In MBH98 it is just there for show, to create the illusion of a hemispheric data base, while the final results are simply the imprint of a sample of bristlecones (dubious as temperature proxies) from western USA. Point (b) is also discussed in our E&E article, but Steve is also demolishing it at greater length at his New Weblog--which by the way is well worth visiting regularly.

* Mann has recently boasted that our 2003 paper in E&E has been completely discredited. In that paper we made 10 claims. Steve has written up a scorecard that goes over the public record and, not surprisingly, reveals Mann's claim to be wishful thinking.

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Many people would like to be kind to others so Leftists exploit that with their nonsense about equality. Most people want a clean, green environment so Greenies exploit that by inventing all sorts of far-fetched threats to the environment. But for both, the real motive is to promote themselves as wiser and better than everyone else, truth regardless.

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