Saturday, February 10, 2007

Occupational risk factors and reproductive health of women

Occupational Medicine 2006; 56: 521-531.
Figa-Talamanca Irene

Chemical agents in the workplace affecting reproductive health:

Metals (Pb, Hg, Cd, Ni or Lead, Mercury, Cadmium, Nickel): Spontaneous abortion (Review by Antilla and Sallmén, 1994)

Lead (Pb) Reduced female fertility / Low birth weight (Sallmén et al., 1995 / Irgens et al., 1998)

Mercury (Hg) - Dental assistants: Spontaneous abortion, reduced female fertility (Rowland et al., 1994)


Organic solvents - Laboratories, industry, dry cleaning: Spontaneous abortion (Review by Lindbohm, 1995)

Toluene, aromatic and aliphatic hydrocarbons, trichloroethylene, tetrachloroethylene: Reduced female fertility (Sallmén et al., 1995)

Tetrachloroethylene - Dry cleaning: Spontaneous abortion (Olsen et al., 1990/Doyle et al., 1997)

Glycol ethers - Semiconductor industry: Spontaneous abortion / Reduced female fertility (Review by Figa-Talamanca et al., 1997)

2-Bromopropane - Electronics industry: Haematological effects / Menstrual disturbances / Spontaneous abortion (Review by Takeuchi et al., 1997)

Petrochemicals - Petrochemical industry: Spontaneous abortion / Reduced birth weight (Xu et al., 1998 / Ha et al., 2002)

Chemical exposures in the Health Care Sector

Ethylene oxide - Dental assistants: Spontaneous abortion / Pre-term birth (Rowland et al., 1996)

Anaesthetic gases - Operating room staff: Spontaneous abortion / Reduced female fertility (Review by Figa-Talamanca, 2000)

Antineoplastic drugs - Oncology hospital staff: Spontanous abortion (Review by Figa-Talamanca, 2000)

Other chemicals

Formaldehyde - Wood processing: Reduced female fertility (Taskinen et al., 1999)

Solvents used in biochemical research laboratories: Pre-term births (Wennborg et al., 2002)


Greenhouse workers have repeatedly (studies in Denmark, Italy and Finland) been shown to be more likely to suffer adverse reproductive effects, probably because exposure to pesticides is higher and more continuous than in other occupations.

Restrepo et al., 1990 (Colombia): Spontaneous abortion

Taskinen et al., 1995 (Finland): Spontaneous abortion

Fuortes et al., 1997 (USA): Female infertility

Curtis et al., 1999 (Canada): Increased time to pregnancy (reduction in female fertility)

Abell et al., 2000 (Denmark): Reduced fecundity

Greenlee et al., 2003 (USA): Increased risk for infertility (herbicides, fungicides)

Physical agents


Ionizing Radiation

Exposure to ionizing radiation in prenatal life is a kwown risk factor for foetal death and congenital defects.

The probability and type of effect depend on dose and the developmental stage of the embryo or foetus.

It is widely accepted that women should avoid all exposures to ionizing radiation in the periconceptional period, as well as during the gestation.

Pregnant women should be protected from doses > 1 mSV during the entire period of gestation (European Union Directive, 2000).

Non-ionizing radiation (ultrasound, microwaves, electricity, magnetic resonance)

Particular interest last 2 decades: electromagnetic field waves (EMF)

Domestic and residential exposes (mobile telephones, electric blankets, power lines)

The issue is still awaiting a definitive answer (Robert, 1999 / Shaw, 2001 / Savitz, 2002).

Effects on the reproductive health of women workers have been studies mainly in 2 areas: Health Care Sector and Use of Video Terminals (VDTs)

Health Professionals (Diganostic and Therapeutic devices) e.g. Magnetic Resonance Operators (Evans et al., 1993) , Physiotherapists (Lerman et al., 2001):

NO consistents epidemiological results (Figa-Talamanca, 2000)

Video Display Terminals (VDTs): of the 13 studies conducted since 1982 only 1 found a statistically significant increase in the risk of spontaneous abortion (Review by Shaw, 2001). It is now agreed that exposure to contemporatory VDTs is suspected to have only a slight association with at best a modest increase in the risk of miscarriage (10-20%). It is unclear whether this is attributable to EMFs or to the other work-related conditions such as ergonomic factors, work stress and long working hours.


Noise-induced stress and its potential interference with the endocrine system has been hypothesized to be a possible risk factor for adverse pregnancy outcomes.

Several studies did find an increased risk in miscarriage, birth defects, pre-term birth and low birth weight (Nurminen, 1995).

The possible negative effect of noise on reproduction is biologically plausible, as well as amenable to prevention.

Ergonomic risk factors

Heavy workload and awkward postures

Heavy workload of the woman has been long been known to be a risk factor not only for spontaneous abortion but also for low birth weight and pre-mature birth of the infant.

Large Canadian study (McDonald et al., 1988)

Other studies in France (Saurel-Cubizolles et al., 1985), the Netherlands (Florack et al., 1993 & 1994), Finland (Taskinen et al., 1990), Fenster et al., 1997

Marbury (1992) stated that although no single ergonomic stressor seems to be strongly associated with birth weight and gestational age, most studies found an effect when several ergonomic stressors were combined.

Physical exercise in healthy pregnant women does not seem to be a risk factor for pre-term birth or low birth weight (Hatch et al., 1998 / Schuller et al., 2001).

Some physically strenuous work conditions (e.g. heavy lifting, frequent bending) might increase the risk of negative pregnancy outcome, especially among women with other risk factors (e.g. with previous foetal losses) or in the presence of other work-related risks.

Work schedule and pregnancy

The studies role of work schedule on the reproductive health of women, often conducted among health care professionals, have not always reached unequivocal conclusions (Nurminen, 1998).

Irregular working hours: slight increase in risk of spontaneous abortion (Axelsson et al., 1989)

Night work: no increased risk in early study by Axelsson et al. (1989)

Shift work & night work: increased risk of spontaneous abortion (Eskenazi et al., 1994)

Evening work: increase risk of spontaneous abortion (Infante-Rivald et al., 1993)

Swedish midwifes (night work / 3 shift schedule): increased risk of spontaneous abortion (Axelsson et al., 1996), pre-term birth (Ahlborg et al., 1996), reduced fecundity (Ahlborg et al., 1996)

It appears that irregular work hours may be associated with a slight increase in the risk of spontaneous abortion an reduced fertility.

Psychosocial work stress

One difficulty in the study of work stress-related reproductive outcomes is that the negative reproductive event may be a source of stress itself, making the direction of the "cause-effect relationship" uncertain.

Some studies have reported associations between work stress and negative effects on reproduction, especially among women under perticular stress or in the presence of other risk factors.

Nurses in the USA & Italy (Hatch et al., 1999): altered cycle length and anovulatory cycles


For a number of exposures at work, the evidence is sufficient to warrant the maximum protection of the pregnant woman: exposures to anaesthetic gases, antineoplastic drugs, toxic metals and specific solvents, pesticides, heavy physical load and irregular work schedules.

For other work risks, such as exposure to non-ionizing radiation, and psychosocial stress, the evidence is often suggestive but not conclusive.

Recent research: association with exogenous or endogenous factors (genetic variation in metabolic detoxification activities)

Methodological problems: defining exposures

Time to pregnancy as a measure of interference with the endocrine system useful tool to detect early reproductive effects

Several other aspects of female reproductive function are not adequately studied:

  • menstrual function
  • very early foetal loss
  • age of menopauze
  • pre-eclampsia
  • pregnancy-induced hypertension
  • post-term birth

Effect of work conditions on endocrine equilibrium of women not yet sufficiently explored (through the use of hormonal markers of ovarian uterine and menstrual function).

It should also be remembered, however, that unreasonable overprotection of women may be both scientifically unsound, as well as disadvantageous to the economic well-being of women.

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