Chapter 14
How Pollution Affects Life

Introduction

Content

Objectives

Quiz

Links

Graphs

glossary

Corrections

Updates

Amendments

Introduction

The chemical industry has produced and disseminated an enormous range of chemical substances in the environment, either on purpose such as pesticides, for technical reasons, or by accident. How are living organisms, plants, animals, and people, able to handle that?

Let us first note that the presence of complex chemical mixtures in the environment is not new to life. The living cell is a fantastic laboratory for the production of an endless variety of molecules. It is not a surprise that we are in general well equipped to handle foreign chemicals.

But still, xenobiotics, foreign chemicals, can be a disadvantage to animals. In some cases the pollutants are very destructive. They damage sensitive parts of the physiology, such as the reproductive system, the nervous system, and the genetic material. Also very minute amounts may be enough to damage an individual, and small damage to a species may be enough to disturb the balance in an entire ecosystem.

The study of how a chemical affects living organisms is the science of toxicology which we will examine in this chapter. Many of the facts gathered in this science have been achieved through animal laboratory experiments. It is however difficult to draw conclusions from data in the laboratory about the effect of a chemical in the environment. Different species react differently and combinations of chemicals interact to potentiate or inhibit each other.

Even if only small amounts of a chemical is found in the environment it may concentrate in animals. Man-made chemicals are often, for technical and economic reasons, more stable than those used in nature, they are persistent, and they are lipophilic, soluble in fat. Persistent lipophilic molecules are difficult to get rid of for the cells, they accumulate in organs and tissues, they stay in the food chains, they are transferred from prey to predator, and even from mother to child.

Hardest hit are thus predators, such as the seals in the Baltic Sea or the birds of prey. Some of these species were almost extinct before it was understood that the reason was toxic chemicals, and measures were taken to stop them. Today we know more about this problem after having studied the havoc that chlorinated organic chemicals make in cellular mechanisms for oxidation, hormone production, and immune defence.

Generally speaking, one may say that man is not seriously threatened by environmental pollutants. Exceptions exist however. The influence from air pollutants especially in cities with much traffic is a health risk in particular for children. We may also point to fish with a high level of mercury or fish with high level of PCB in the Baltic Sea.

However, chemicals in the work place may be quite dangerous. Thus, occupational medicine is important and has strict rules for many chemicals in the environment. Public health takes a wider approach to see what factors are decisive for human health. It is clear that the largest "pollution" factor for health by far is cigarette smoking, which may lead to both respiratory problems, heart disease, and cancer.

It is possible to avoid many of the chemicals that are known to be very dangerous, and there will be more and more restrictions on the chemical industry and consumers. In May 2001 a convention to globally outlaw the 12 most toxic chemicals was reached.