And remember that the natural substances we encounter can sometimes change a gene. Scientists say that some of our genes were modified by conditions hundreds of years ago and were passed to us from our great, great grandparents.

Today, the chemicals or X-rays we need and use also can affect genes, especially if people are careless about how they handle these things. Smoking causes changes in the genes of our lungs and other places in the body. Such a poison can garble a gene's code. The poison can affect the message that a gene sends to cells to tell them what to do, how to assemble, and how to grow. It can undermine the cell's way of correcting mistakes that can occur in the DNA - the chemical chain that carries our genes.		DNA


Everyone responds differently

What gene variations make people respond differently?

Researchers are studying how different people respond differently to harmful substances. They have found that common differences in genes can affect the human body's responses.

For example, some genes signal the making of proteins called enzymes, in the lungs. Ordinarily these enzymes, or active substances, destroy some of the cancer-causing substances in tobacco smoke. But researchers have found a gene variation that may reduce these enzymes and make people more susceptible to lung cancer.


Something similar may happen in emphysema (em-fizz-ZEEM-a), a disease in which a person's lung tissue deteriorates and he or she has a hard time breathing. Tobacco smoke, solvents used in factories, and other chemicals and air pollutants can produce changes in lung tissue and cells and even in the molecules the cells are made of. Variations of a gene may mean more - or less - production of an enzyme that protects against these changes.
Finding a gene with a variation that can cause a disease can help in the design of drugs to counter it. Some scientists also look toward correcting some diseases by substituting a "good" gene before a baby is born.

Learning more about these variations:

At the National Institute of Environmental Health Sciences, researchers want to find out more about these variations in 200 or more of the genes that make us more, or less, sensitive to the substances around us. To do this, they have developed a project called the " Environmental Genome Project" with other parts of the National Institutes of Health.

A few people may have a variation that make them very resistant to a chemical.

A few may have a variation that gives them a high chance of being hurt by the same substance.

Most of us may be somewhere in between.

The Environmental Genome Project meshes with the Human Genome Project, which seeks to map every one of the 70,000 or more genes in humans - the whole instruction book for "human beings." (About half the human genes have now been located.)

The newer "Environmental Genome Project" looks at genes that have already been located. These particular genes have been shown to play a role in how we react to environmental substances. Scientists want to see how these genes differ in different people, what percentage of us have which variations, and what these variations mean in terms of our reactions.

These are not genes that give clear orders for a disease regardless of other factors. Instead, these genes determine our weakness or strength in the face of various metals, natural and human-made chemicals, radiation, and such. They are called "susceptibility genes."



Susceptibilities differ!

The scientists in this project hope to discover:

Are the people with "such-and-such" a gene variation more likely to be harmed by a chemical? Are the people with a different variation less at risk? How many people have this variation? How many have another?

The Environmental Genome Project will help answer the "Why me?" question. A smoker told he has developed a fatal lung cancer asks this question because he knows of people who smoked as much and may have a hacking cough or breathlessness, but do not have lung cancer.

Or perhaps you and your brother Joe work at a job around smoke or chemicals or smelly glues. Why might one of you be hurt and the other not?

To find out how many of us have gene variations that protect us or, in other cases, make us susceptible, scientists test blood samples from several hundred volunteers representing the American people as a whole. The blood is tested for variations in as many genes as the scientists are studying.

Tomorrow ...

In the future, will doctors give you a list of foods, chemicals, metals or other substances to avoid, based on how you react to them? Someday, very probably!

Most likely, the information will help you avoid some natural hazards you're susceptible to, much as people who aren't strong swimmers try to stay out of deep water, or people with diabetes avoid sugar. And industry and unions along with state and federal regulators will have information to ensure that even those of us who react the most will be protected.

One way or another, we should gain a much better idea of which of us is at most risk - and what precautions need to be taken to best protect us. This knowledge may help us prevent - or avoid - a lot of disease and disability, producing a better, safer future for us all.

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Many of the differences between people are due to our genes. The National Institute of Environmental Health Sciences has two big jobs:

  1. Scientists look for things in our world that may hurt They discover what harm these substances can do and how we can get rid of these poisons or avoid them.

  2. These scientists study how we react to these harmful things:
    • Are we sensitive or resistant?
    • do you and I respond the same?

Special thanks to former NIEHS Scientific Director J. Carl Barrett
Publication Art by Susan Spangler.

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