The Effects of Workplace Hazards on
Male Reproductive Health
The Effects of Workplace Hazards on
Male Reproductive Health
Many factors can contribute to producing healthy children. It
is well known that the health of an unborn child can suffer if
a woman fails to eat right, smokes, or drinks alcohol during pregnancy.
It is not well known, however, that a man's exposure to substances
in the workplace can affect his ability to have healthy children.
This document provides general information about reproductive hazards, an explanation of how substances in the workplace can cause reproductive problems in men, and suggestions for preventing exposure to reproductive hazards. For more information about the topics covered in this document, call toll free:
DHHS (NIOSH) Publication No. 96-132
Substances that affect the ability to have healthy children are
called reproductive hazards.
Radiation, many chemicals, drugs (legal and illegal), cigarettes,
and heat are examples of reproductive hazards.
A number of workplace substances such as lead and radiation have
been identified as reproductive hazards for men (see Table 1).
However, there is no complete list of reproductive hazards in
the workplace. Scientists are just beginning to understand how
these hazards affect the male reproductive system. Although more
than 1,000 workplace chemicals have been shown to have reproductive
effects on animals, most have not been studied in humans. In addition,
most of the 4 million other chemical mixtures in commercial use
remain untested.
Although studies have found that workplace exposures affect the
reproductive system in some men, these effects do not necessarily
occur in every worker. Whether individuals are affected depends
on how much of the hazard they are exposed to, how long they are
exposed, how they are exposed, and other personal factors.
Reproductive issues are likely to receive more attention in the
future because they are included in the National Occupational
Research Agenda coordinated by NIOSH. As one of the 21 topics
included in the Agenda, research on reproductive issues will undoubtedly
increase nationwide. For copies of the Agenda, contact NIOSH at
1-800-356-4674.
Harmful substances can enter the body by inhalation, contact with
the skin, or ingestion (if workers do not properly wash their
hands before eating, drinking, or smoking).
Workplace substances that affect male workers may also indirectly
cause harm to their families. Certain substances unintentionally
brought home by a worker may affect a woman's reproductive system
or the health of an unborn child. For example, lead brought home
from the workplace on a worker's skin, hair, clothes, shoes, tool
box, or car can cause severe lead poisoning among family members
and can cause neurobehavioral and growth effects in a fetus.
Observed effects
_________________________________________________________________
Type of Exposure Lowered number Abnormal sperm Altered sperm Altered hormones/
of sperm shape transfer sexual performance
Lead X X X X
__________________________________________________________________________________________
Dibromochloropropane X
__________________________________________________________________________________________
Carbaryl (Sevin ) X
__________________________________________________________________________________________
Toluenediamine and X
dinitrotoluene
__________________________________________________________________________________________
Ethylene dibromide X X X
__________________________________________________________________________________________
Plastic production X
(styrene and acetone)
__________________________________________________________________________________________
Ethylene glycol monoethyl X
ether
__________________________________________________________________________________________
Welding X X
__________________________________________________________________________________________
Perchloroethylene X
__________________________________________________________________________________________
Mercury vapor X
__________________________________________________________________________________________
Heat X X
__________________________________________________________________________________________
Military radar X
__________________________________________________________________________________________
Kepone** X
__________________________________________________________________________________________
Bromine vapor** X X X
__________________________________________________________________________________________
Radiation** (Chernobyl) X X X X
__________________________________________________________________________________________
Carbon disulfide X
__________________________________________________________________________________________
2,4-Dichlorophenoxy acetic X X
acid (2,4-D)
__________________________________________________________________________________________
*Studies to date show that some men experience the health effects listed here from workplace exposures. However, these effects may not occur in every worker. The amount of time a worker is exposed, the amount of hazard to which he is exposed, and other personal factors may all determine whether an individual is affected.
**Workers were exposed to high levels as a result of a workplace
accident.
To understand how reproductive hazards affect a man's ability
to have healthy children, it is important to understand how the
male reproductive system works.
The testicles have two important functions: (1) they produce the
hormone testosterone, which produces the deep male voice, beard,
and sex drive; and (2) they produce sperm.
After the sperm are made (in about 72 days), they are stored in
the epididymis, the outer structure of the testicles. The sperm
remain in the epididymis for about 15 to 25 days. While there,
they mature and develop the ability to swim. If the sperm are
not ejaculated, they eventually die and are absorbed by the body.
When a man ejaculates, the mature sperm cells move through the
vas deferens (the tube cut in a vasectomy) and past the seminal
vesicles and prostate gland. The seminal vesicles and the prostate
provide most of the liquid in semen.
The semen is deposited in the vagina and the sperm must then swim
through the cervix into the uterus and up into the fallopian tubes.
If an egg is present, it is fertilized in the fallopian tubes.
The fertilized egg then moves down to the uterus, where it attaches
to the wall and continues to grow. If no egg is present, the sperm
may live within the uterus for up to 2 days.
Number of Sperm
Some reproductive hazards can stop or slow the actual production
of sperm. This means that there will be fewer sperm present to
fertilize an egg; if no sperm are produced, the man is sterile.
If the hazard prevents sperm from being made, sterility is permanent.
Sperm Shape
Reproductive hazards may cause the shape of sperm cells to
be different. These sperm often have trouble swimming or lack
the ability to fertilize the egg.
Sperm Transfer
Hazardous chemicals may collect in the epididymis, seminal vesicles,
or prostate. These chemicals may kill the sperm, change the way
in which they swim, or attach to the sperm and be carried to the
egg or the unborn child.
Sexual Performance
Changes in amounts of hormones can affect sexual performance.
Some chemicals, like alcohol, may also affect the ability to achieve
erections, whereas others may affect the sex drive. Several drugs
(both legal and illegal) have effects on sexual performance, but
little is known about the effects of workplace hazards.
Sperm Chromosomes
Reproductive hazards can affect the chromosomes found in sperm.
The sperm and egg each contribute 23 chromosomes at fertilization.
The DNA stored in these chromosomes determines what we will look
like and how our bodies will function. Radiation or chemicals
may cause changes or breaks in the DNA. If the sperm's DNA is
damaged, it may not be able to fertilize an egg; or if it does
fertilize an egg, it may affect the development of the fetus.
Some cancer treatment drugs are known to cause such damage. However,
little is known about the effects of workplace hazards on sperm
chromosomes.
Pregnancy
If a damaged sperm does fertilize an egg, the egg might not develop
properly, causing a miscarriage or a possible health problem in
the baby. If a reproductive hazard is carried in the semen, the
fetus might be exposed within the uterus, possibly leading to
problems with the pregnancy or with the health of the baby after
it is born.
Employers have a responsibility to protect their workers. However,
because so little is known about reproductive hazards, workers
should also take the following steps to ensure their own safety:
or to the CDC home page.
