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Reproductive hazards can be divided into two groups, those which cause reproductive effects, such as chemicals which impair sperm production and fertility, and those which damage the developing foetus. Reproductive hazards affect both men and women at work.

Several chemicals are known to make men less fertile by affecting the production of sperm. Other substances can reduce sex drive or cause impotence. In women, some occupational exposures are associated with irregular periods, increased rates of miscarriage, or premature or low birth weight babies (which are less healthy and more likely to die before their first birthday than other babies), or deformed babies. Chemicals that cause birth defects are known as teratogens, and the effects they have as 'teratogenic'. These can include visible (structural) deformities or functional abnormalities, like learning difficulties.

As well as the dose a woman is exposed to, the stage of her pregnancy at which the exposure takes place is important. The developing foetus is very vulnerable to teratogens during the first three months of pregnancy, precisely the time when a woman may not realise she is pregnant. Because of this, reproductive hazards at work should be identified before women become pregnant.

Only about 4% of the chemicals in commercial use in the USA have been tested for teratogenicity. But of those tested on animals 37% are clearly, probably or possibly teratogenic (Stacey p.109).

Reproductive effects have been reported in many occupational groups, including health care workers, laboratory and dental technicians, factory workers, pulp and paper industry workers, construction workers, transport and communication workers, printers, plastics industry workers, and lead production workers.

* The considerable variation in reproductive and developmental toxicity in different species makes it difficult to apply the results of animal tests to humans.

In the UK and the rest of Europe, safety data sheets and labels should contain information on reproductive hazards, including the risk phrases "R46 (may cause heritable genetic damage)", "R61 (may cause harm to the unborn child)", "R63 (possible risk of harm to the unborn child)" and "R64 (may cause harm to breast-fed babies)" required by the CHIP Regulations (see pp 63-64).

The results of two large studies on rates of miscarriage (spontaneous abortion) were published in 1997. One, funded by the HSE, looked at dry cleaning workers in the UK. The other examined all previously published research on women exposed to anaesthetic gases at work. Although perchloroethylene has been used as an industrial solvent for over 50 years, and in dry cleaning for more than 30 years, concern over its effects on pregnant women arose after a Finnish study in 1980 which found dry cleaning workers twice as likely to miscarry as other women. The UK study looked at 7305 women who worked in dry cleaners, and found they were half as likely again as other women to report that they had a miscarriage (P. Doyle et al., Spontaneous abortion in dry cleaning workers potentially exposed to perchloroethylene, Occupational and Environmental Medicine, 1997, 54, 848-853). A similarly increased risk of miscarriage was found for women exposed to anaesthetic gases (J.-F. Boivin, Risk of spontaneous abortion in women occupationally exposed to anaesthetic gases: a meta-analysis, Occupational and Environmental Medicine 1997, 54, 541-548).

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