Health Guide

Body Chemical

Our bodies contain a 'chemical cocktail. 'All bodies must to survive. But the mere presence of chemicals should not set off alarms
Salicylic acid is a chemical.

 Perhaps a surprising statement to some. Why? Because the word "chemical" isn't preceded by a pejorative adjective such as "dangerous," "poisonous" or "toxic." That's unusual these days. We're more accustomed to seeing reports, such as the recent Polluted Children, Toxic Nation generated by Environmental Defence, a non-governmental organization, which highlight the "toxic chemicals" that enter our bodies from our polluted environment.

The Environmental Defence paper, released to considerable media coverage earlier this month, prompted federal Environment Minister Rona Ambrose to agree to have her own blood tested for toxic chemicals, the same tests Environmental Defence had done for members of several families. The minister promised to "take some measures" to address the problem of "toxins" in our bodies.

Actually, without appropriate context, "toxic chemical" is a meaningless term -- a distinction the Environmental Defence study fails to make.
Take salicylic acid. It occurs naturally in a variety of fruits and plants, and is also formed in our body when Aspirin is metabolized. Indeed, it is responsible for the physiological effects of Aspirin, which include reducing the risk of blood clot formation. That's why Aspirin is used to treat a heart attack, and is commonly taken in small doses to prevent one. But in an overdose, salicylic acid can kill. Before childproof packaging was introduced, Aspirin poisoning was a common cause of death in children.
 

So how do we react if a test detects salicylic acid in our blood? Panic because of the presence of a "toxic chemical" or relief because of possible protection against heart disease? Of course, without having some sort of reference value, there can be no appropriate reaction. To decide whether to laugh or cry, we would want to know what blood levels of salicylic acid have been linked to risk, and what levels to protection from disease. The mere presence of the chemical says nothing. As Paracelsus insightfully and wisely noted some 500 years ago, "only the dose makes the poison."
Similar arguments apply to the numerous other chemicals, both man-made and natural, that find their way into our body from the environment. Certainly, these include compounds found in paints, dyes, pesticides, cleaning agents, air fresheners, gasoline vapours, plasticizers and flame retardants.

But consider also that a single apple is composed of more than 300 compounds, the natural building blocks of the fruit. These include the likes of acetone and formaldehyde, both of which in the proper context can be labeled as "toxic chemicals," but of course the amounts found in apples are way too tiny to present a risk. Yet a blood test would reveal their presence.
Consuming celery, mushrooms, roast beef or beer would taint the blood with furocoumarin, hydrazine, 2-amino-3-methylimidazo[4,5-f]quinoline and ethyl carbamate, all known natural carcinogens. And there would be arsenic as well. This carcinogen occurs naturally in meat, fish and cereals. But our bodies do not distinguish between natural and synthetic carcinogens. What matters is whether a toxic dose has been reached.

Numbers matter. Let's take flame retardants as an example. Polybrominated diphenyl ethers (PBDEs) have been protecting fabrics, furniture, computers and various other consumer items from fire since the 1970s. These chemicals are estimated to save about 300 lives a year but the question is how many people, if any, are put at risk by their ubiquitous presence? Toxicological studies have shown that these chemicals can impair reflexes and learning abilities in rodents, and can also delay their puberty by interfering with thyroid function.
PBDE levels in the environment have been rising and virtually all of us have some of these chemicals in our body. Indeed, as Environmental Defence has shown, there may be as much as 0.5 micrograms per litre in an individual's blood plasma. What does this mean? For one, it means that chemists have developed amazing abilities to determine tiny concentrations. We are talking about finding the proverbial needle in the haystack. It also means that the five litres of blood in our body harbour 2.5 micrograms of flame retardant.

That is roughly 1/1,000th the mass of a grain of sand. Pretty impressive technology. What, though, does it say about any health risk? Without any further information, not much.
We certainly would be concerned if data showed that patients with some sort of disease were more likely to have higher blood levels of PBDEs than the rest of the population, and we would then want to know at what blood levels risk becomes significant. But we do not have any such data for humans. We can, however, make an educated guess based on rodent experiments. A common way to measure toxicity is to determine the dose below which no adverse effects are seen. For behaviourial effects in mice or rats, this is of the order of one milligram PBDE per kilogram of body weight. That's far more PBDE than is found in humans!

These concepts should be kept in mind when we face headlines such as "Canadians' Blood Holds Chemical Cocktail" or "At Age 10, He Tests Positive for 25 Toxic Chemicals," prompted by the Environmental Defence investigations. In one case, laboratories tested for 88 "toxic chemicals" in blood taken from 11 Canadians, and in a subsequent study 68 substances were assayed in the blood of five families from across the country. Environmental Defence's reports of the results, sensationally titled Toxic Nation and Polluted Children, Toxic Nation, provide a good discussion of the chemicals tested for, their possible sources and amounts detected.
Much was made of the fact that more than half the chemicals tested for were found to be present to some degree. But curiously, the reports do not mention any reference values. Not even when these exist. For example, the median value of mercury detected was well below 30 nanomoles per litre, the level at which, according to the Centers for Disease Control (CDC) in the United States, we should become concerned.

There is also the question of using blood levels to estimate risk. In fact, tissue levels are a much better measure of body burden, but Environmental Defence did not measure these.
In any case, based on its data, Environmental Defence forecasts a dismal future, clouded by rising cancer rates. But there is selectivity in the way the data is presented. It refers to increases in rates of prostate and breast cancer as well as non-Hodgkin's lymphoma over the past couple of decades without mentioning declines in stomach cancer, Hodgkin's disease or leukemia. Cancer is a complex, multifactorial disease and no unambiguous data link it to non-industrial exposure to synthetic chemicals. Researchers estimate that perhaps 1% of premature cancers can be linked to industrial products, with the majority of cases being caused by unbalanced diet (35%), tobacco (30%), infections (10%), sexual behaviour (7%), occupational exposure (5%) and alcohol (3%).

Environmental Defence did not connect the presence of "toxic chemicals" in the blood of the volunteers it studied to any disease. Indeed, there is no mention of health problems in any of the subjects. But nevertheless, just the finding of these chemicals in the blood, albeit in trace amounts, has triggered some emotionally charged reactions. One woman whose blood showed the presence of some perfluorinated compounds threw out her single Teflon pan, believing it to be the culprit. Actually, the major chemical in question, perfluorooctanoic acid (PFOA), is used in the manufacture of Teflon, but is not found in the finished product. There is no doubt that PFOA is an environmentally persistent chemical, and concern about it is valid. That's why manufacturers will phase it out and find other ways to produce the non-stick coating on cookware. But throwing out a Teflon pan just increases the chance of eating burned food with its cargo of known carcinogens.

None of this is meant to suggest that "biomonitoring," such as carried out by Environmental Defence or by the highly respected Centers for Disease Control, is not important. It does provide information that may eventually be useful. That's why every two years, the CDC selects several thousand people at random and carries out a comprehensive urine and blood analysis for some 150 different compounds that may enter the body from the environment. The hope is that we may be able to get a handle on why conditions such as autism, asthma, prostate cancer and low sperm count are increasing. Could phthalates leaching from plastics be involved? And if so, specifically which phthalate? Although di(2-ethylhexyl)phthalate and diisononyl phthalate may sound very similar, their toxicological properties are very different. You can't paint all phthalates with the same broad brush.

We also want to keep a close eye on bisphenol A (BPA), a compound used in the manufacture of polycarbonate plastics, found in a wide array of products ranging from compact discs to those large water jugs that sit atop coolers. In animal studies, very small doses of BPA have been shown to have estrogenic effects, causing genetic changes in rat fetuses that can affect the prostate gland. BPA is found in most humans but no study yet has found an association between blood levels and prostate cancer. And how do BPA's estrogenic effects compare with that of the naturally occurring estrogens dumped into our water systems through human urine? Nobody knows.
Environmental Defence's overall conclusion is to urge us to follow the "precautionary principle." Make companies prove their products are safe before releasing them to the marketplace. An appealing notion indeed, but scientifically unrealistic. Science cannot prove a negative. It cannot prove that adverse effects are not possible any more than it can prove that unicorns do not exist. All scientists can do is make educated guesses about risk-benefit ratios.

Biomonitoring may indeed eventually identify some specific chemical culprits which, when present in our blood in excess of some critical amount, do impair our health. We may find that some specific pesticide, but not all, can cause a problem. Or that we may be better off using one type of plastic over another. Or that our concern should focus on the presence in our blood of ochratoxin, zearalenone or fumonisin, all of which are established carcinogens. These are not synthetic chemicals, they are mould metabolites that contaminate grains and undoubtedly would be found in our blood to some extent if we only bothered to look for them.

But for now, let's not let the mere presence of chemicals in our blood distract us from the known keys to improving health. Exercise, limiting alcohol intake, eliminating smoking, eating more fruits and vegetables, and perhaps most importantly cutting back on excess calories, have all been scientifically shown to increase longevity. Let's also remember that excessive worry, such as about the finding of trace amounts of "toxic chemicals" in our blood, can have a negative impact on health. And finally, we can take some comfort in the fact that, despite the dire picture sometimes painted of our society with "toxic chemicals," our average life expectancy increases every year.
Joe Schwarcz, PhD, is director, McGill University Office for Science and Society.
Source: Financial Post