Chemicals and your health

The term "chemical" applies to all the basic substances that make up the world around us, including the more than one hundred fundamental elements, such as iron, lead, mercury, carbon, oxygen, nitrogen. Chemical compounds, or combinations of different elements, include such things as water, acids, salts, and alcohol. Many of these compounds occur naturally.

A "chemical reaction" has been defined as "a process in which one substance is chemically converted to another." Fire is a chemical reaction; it converts one combustible substance—paper, gasoline, hydrogen, and so forth—into a totally different substance or substances. Many chemical reactions occur unceasingly, both around us and inside us.

THIS century could well be called the age of chemistry. Man-made chemical compounds have changed our lives. Our homes, offices, and factories are filled with aerosols, artificial sweeteners, cosmetics, dyes, inks, paints, pesticides, pharmaceuticals, plastics, refrigerants, synthetic fabrics—the list could fill volumes.
To satisfy the world's demand for these products, the annual global production of chemicals, according to the World Health Organization (WHO), amounts to about $1.5 trillion. WHO reports that some 100,000 chemicals are now on the market and that from 1,000 to 2,000 new ones are added each year.

However, this flood of chemicals invites questions regarding how they affect the environment as well as our own health. Clearly, we are sailing into uncharted waters. "We are all part of an experimental generation, and the full effects will not be known for decades to come," said one doctor.

More Chemicals, More Risks?

The people most often affected by chemical pollutants, observes WHO, are "poor, illiterate people with little or no access to appropriate training or basic information on the risks posed by chemicals to which they are exposed directly or indirectly every day." This is especially true of pesticides. But we are all affected by chemicals.

Some 20 percent of California's water wells, says the book A Green History of the World, have pollution levels, including pesticides, above official safety limits. "In Florida," the book adds, "1,000 wells have been closed because of contamination; in Hungary 773 towns and villages have water that is unfit for consumption, in Britain ten per cent of aquifers are polluted above World Health Organisation safety limits and in parts of both Britain and the United States tap water cannot be given to new born babies because of high nitrate levels."

Mercury is another useful but potentially toxic chemical. It finds its way into the environment through sources ranging from industrial smokestacks to billions of fluorescent lights. Similarly, lead can be found in many products, from fuel to paint. But like mercury, it can be toxic, especially to children. Exposure to leaded emissions may shave up to "four points from the I.Q." of the average child, says one report from Cairo, Egypt.

According to the United Nations Environment Programme, each year some 100 tons of mercury, 3,800 tons of lead, 3,600 tons of phosphates, and 60,000 tons of detergents enter the Mediterranean Sea as a result of human activities. Understandably, the sea is in crisis. But it is not alone. In fact, the United Nations declared 1998 the International Year of the Ocean. Worldwide, all oceans are in trouble, particularly because of pollution.

While chemical technology has given us many helpful products, we use and dispose of many of them at considerable cost to the environment. Have we, as one newspaper columnist recently said, made ourselves "hostages to progress"?

WE MAKE many decisions in life by weighing advantages against disadvantages. For example, many people buy a car because of the convenience it offers. But against that convenience they have to weigh the cost of owning the car—insurance, registration, depreciation—and of keeping the car roadworthy. They also have to consider the risk of injury or death due to accidents. The situation is much the same with synthetic chemicals—their advantages have to be weighed against their disadvantages. Take as an example the chemical called MTBE (methyl tertiary butyl ether), a fuel additive that enhances combustion and cuts vehicle emissions.
Thanks in part to MTBE, the air in many cities in the United States is the cleanest it has been in years. But cleaner air "has come at a price," reports New Scientist. This is because MTBE is a potential carcinogen, and it has leaked from tens of thousands of underground gasoline storage tanks, often contaminating groundwater. As a result, one town now has to bring in 82 percent of its water from outside, at a cost of $3.5 million a year! New Scientist says that this disaster "could become one of the US's most serious groundwater pollution crises for years."
Some chemicals have been banned and taken off the market altogether because of the damage they cause to the environment and to health. 'But why,' you may ask, 'does this happen? Are not all new chemicals thoroughly tested for toxicity prior to release?'

Problems With Tests for Toxicity

Actually, testing chemicals for toxicity is a blend of science and guesswork. "Risk assessors do not know how to draw a sharp line between 'safe' and 'unsafe' exposures to any chemical," says Joseph V. Rodricks in his book Calculated Risks. That is true even of drugs, many of which are produced synthetically. "Even the most careful testing," says The World Book Encyclopedia, "cannot always reveal the possibility that a drug might produce an unexpected harmful effect."
Laboratories have certain built-in limitations. They cannot, for example, fully simulate a chemical's behavior in the diverse and complex outside world. The world outside the laboratory abounds with hundreds, even thousands, of different synthetic chemicals, many of which can interact with one another as well as with living things. Some of these chemicals are innocuous on their own, but if they join together, outside or inside our bodies, they can produce new, toxic compounds. Certain chemicals become toxic, even carcinogenic, only after the body's metabolism processes them.

How do risk assessors try to determine a chemical's safety in the light of such challenges? The standard method has been to give laboratory animals a measured dose of the chemical and then try to apply the results to humans. Is this method always reliable?

Are Tests on Animals Reliable?

Besides raising ethical questions regarding cruelty to animals, testing toxins on animals raises other questions. For instance, different animals often react quite differently to chemicals. A small dose of highly toxic dioxin will kill a female guinea pig, but that dose has to be increased 5,000 times to kill a hamster! Even closely related species like rats and mice react differently to many chemicals.

So if the reaction of one animal species is no sure predictor of the reaction of another species, how certain can researchers be that a particular chemical will be safely tolerated by humans? The fact is, they cannot really be certain.
Chemists surely have a difficult task. They have to please the people who want their creations, appease those concerned about animal welfare, and satisfy their own consciences that their products are safe. For these reasons, some laboratories are now experimenting with testing chemicals on human cells in culture. Time will tell, however, if this makes reliable guarantees of safety possible.

When Laboratory Tests Fail

The pesticide DDT, still widely found in the environment, is one example of a chemical that was wrongly declared safe when first released. Scientists later learned that DDT tends to remain in organisms a long time, which is also the case with other potential toxins. What are the tragic consequences of this? Well, the food chain, made up of millions of tiny creatures, then fish, and finally birds, bears, otters, and so on, becomes a living funnel, concentrating toxins in the final consumers. In one case, a population of grebes, a species of water bird, was unable to hatch a single chick for over ten years!