How Toxic Chemicals Harm Us 321
How Toxic Chemicals Harm Us
Whether or not a person will be harmed by toxic
chemicals, and the kind of health problem that may
be caused, depends on many things:
• what kinds of chemicals and the amounts he or
she is exposed to
• how long the exposure lasts
• his or her age, body weight, height, and sex
• his or her general state of health at the time of
the exposure
The danger from toxic chemicals is strongest at times
when our bodies are growing or changing rapidly:
• when a baby is forming in the womb
• when a child is young and growing quickly
• when a teenager’s (adolescent’s) body is going
through rapid changes
Every member of this family
is affected by the chemical
factory in their town — some
more, some less.
• when an older person’s body slows down and is less able to filter poisons
The effects of toxic chemicals on a person may be severe, such as serious birth
defects or cancer. Other effects may be harder to see, such as difficulty learning,
slow growth, allergies, difficulty having children, and more frequent illness.
It is often difficult to know whether a certain health problem was caused
or was made worse by toxic chemicals. Although toxic chemicals have been
proven to cause many different illnesses, because we are exposed to so many
chemicals at so many different times, proving that one particular exposure was
responsible for an illness is difficult. But many illnesses are more common in
places where people are regularly exposed to toxic chemicals.
Even very small amounts cause harm
Traditionally, doctors and scientists follow the rule, “the dose makes the
poison.” This means that more of a substance has a stronger effect, and less of
it has a weaker effect. For example, poisons such as arsenic or cyanide are only
toxic if a person eats too much of them. Even most medicines, like aspirin, are
helpful when taken in small amounts, but can be harmftul in large amounts.
But even very small amounts of some toxic chemicals can be very harmful.
Some chemicals, such as POPs and PCBs, are not safe in any amount (see
pages 340 to 342).
A Community Guide to Environmental Health 2012