Voortplanting, zwangerschap en werk

Tijdschrift voor Bedrijfs- en Verzekeringsgeneeskunde (TBV) 2006; September; 14 (9): 386-427.

Een recent nummer (September 2006) van het Nederlandse Tijdschrift voor Bedrijfs- en Verzekeringsgeneeskunde (TBV) is bijna volledig gewijd aan de topic Voortplanting (reproductie), zwangerschap en werk.

Themanummer

• Voortplanting, zwangerschap en werk. Brand T, Stinis HPJ.
• De invloed van fysieke belasting, stress en ploegendienst op de voortplanting. Brand T, Pal T, Zweerman G.
• Epidemiologisch onderzoek naar reproductiestoornissen en beroepsmatige blootstelling in Nederland. Roeleveld N.
• Arbozorg rond zwangerschap ook op man richten.
• Zwangerschap, infectieziekten en werk. Stinis HPJ.
• Vruchtbaarheid bij werknemers in kassen.
• Fysische werkfactoren en zwangerschapsuitkomsten. de Joode EA, Brand T.
• Er werken wel veel jonge vrouwen. Sorgdrager B.
• Zoeken en vinden van informatie over reproductie en arbeid. Schaafsma FG, Zweerman G.
• Werken tijdens zwangerschap en de periode postpartum, wetgeving. Over een bal die moet gaan rollen. van Beukering MDM.
• Best practices. Brand T, Stinis HPJ.

Samenvatting

Stoornissen in het voortplantingsproces door beroepsmatige belasting omvatten breed gebied, zowel wat betreft oorzaken als afwijkingen.

Schade

• VOOR de bevruchting (verminderde fertiliteit)
• TIJDENS de zwangerschap (miskraam)
• NA de geboorte (laag geboortegewicht, aangeboren afwijkingen)

Beroepsmatige blootstelling

• Fysieke belasting
• Psychische belasting
• Chemische stoffen
• Biologische agentia
• Fysische factoren

De invloeden van metalen en invloed van factoren in het werk op de borstvoeding komen niet aan bod.

Artikel van Brand T, Pal T, Zweerman G

• Fysieke belasting, psychische belasting en onregelmatige diensten verhogen de kans op vroeggeboorte en een laag geboortegewicht.
• Meer kans op zwangerschapshypertensie en pre-eclampsie bij fysiek of psychisch belastend werk.
• Psychische belasting en ploegendienst kunnen de menstruele cyclus versturen.
• Minder negatieve zwangerschapsuitkomsten bij aanpassing van de werkzaamheden voor de 24e week van de zwangerschap.
• In hoeverre het werk van zwangere vrouwen in Nederland bijtijds wordt aangepast, zal moeten blijken uit nader onderzoek.

Interessante referenties: Koemeester et al., 1995 / Mozurkewich et al., 2000(meta-analyse) / Croteau et al., 2006

Artikel van Roeleveld N

• In de afgelopen 20 jaar zijn in Nederland diverse onderzoeken gedaan naar de schadelijke effecten van beroepsmatige blootstelling voor vruchtbaarheid en zwangerschap, met name bij kapsters, ziekenhuispersoneel, schilders en mensen werkzaam in de agrarische sector.
• In dit onderzoek werden beroep en blootstelling van moeder en/of vader geassocieerd met verminderde vruchtbaarheid, miskramen, laag geboortegewicht, aangeboren afwijkingen en functionele ontwikkeling van het kind.
• Het is onduidelijk of bij de huidige blootstellingsniveaus van bijv. anaesthesiegassen, cytostatica, bestrijdingsmiddelen en organische oplosmiddelen, vergelijkbare effecten op de reproductie te verwachten zijn.

Interessante referenties: Roeleveld et al., 1990 (review) / Roeleveld, 1991 (proefschrift mentale retardatie kinderen en blootstelling ouders) / Peelen et al., 1999 / Kersemaekers, 1998 (proefschrift kapsters) / Bretveld, 2006 (proefschrift personeel kassen)

Arbozorg rond zwangerschap ook op man richten.

Blootstelling van de vader aan oplosmiddelen, pesticiden, metalen of straling VOOR de conceptie of TIJDENS de zwangerschap, kunnen een negatief effect hebben op de vruchtbaarheid of de zwangerschapsuitkomst.

Artikel van Stinis HPJ

• TORCHES (Toxoplasma, Rubella, Cytomegalievirus; Herpes, Enteroviri en Syfilis) en VLAP (Varicella, ziekte van Lyme, AIDS en Parvovirus) bedreigen iedere zwangere werkneemster.
• Zwangere als risicogroep bij infectieziekten in iedere RI&E.
• Vaccinatie moet altijd, en dit geldt ook voor zwangere werkneemsters.

Vruchtbaarheid bij werknemers in kassen

• Proefschrift van Bretveld aan de Universiteit van Nijmegen

Fertility among greenhouse workers.

• Vrouwen hebben een hoger risico op een miskraam en mannen een hoger risico op verminderde zaadkwaliteit (met name alstroemeria's en amarylissen).
• Adviezen: blootstelling beperken (gebruik handschoenen, pesticiden vervangen door minder schadelijke methodes, beperken werkuren, voorlichting geven)

Artikel van de Joode EA, Brand T

• Het is belangrijk preventief te werk te gaan als het gaat om het blootstellen van een zwangere vrouw aan lawaai, straling, extreme temperaturen en trillingen tijdens het werk.
• Toekomstig goed opgezet onderzoek naar deze fysische werkfactoren is van belang om een duidelijk beeld te schappen van de invloed van deze factoren op zwangerschapsuitkomsten.
• Een zwangere werkneemster mag gedurende haar zwangerschap:

- niet aan meer dan 1 mSv straling blootstaan bovenop de altijd aanwezige achtergrondstraling;

- niet aan meer lawaai worden blootgesteld dan 80 dB(A) gedurende maximaal 8 uur per dag;

- niet worden blootgesteld aan klimaatomstandigheden, die beschouwd worden als onbehaaglijk;

- niet worden blootgesteld aan trillingen met een versnelling boven de 0,25 m/s2 gedurende 8 uur

Interessante referenties: Mamelle et al., 1984 / McDonald et al., 1988 / Zhang et al., 1992 / Luke et al., 1994 / Nurminen, 1995 / Morrissey, 1998 / Murray et al., 2000 / Elter et al., 2004 / Judge et al., 2004

Artikel van Sorgdrager B

Reprotoxische effect van methanol - Laborante met gehandicapte zoon

Rapport van de Gezondheidsraad over Methanol (2006)

Methanol classificeren in categorie 2 (stoffen die dienen te worden beschouwd alsof zij bij de mens ontwikkelingsstoornissen veroorzaken)

R61: stof kan schade veroorzaken bij het ongeboren kind

Hoe krijg je de "nul-blootstelling" voor elkaar?

Moet je alle vrouwen met kinderwens elders laten werken?

Artikel van Schaafsma FG, Zweerman G

• Korte uitleg en voorbeelden ter beantwoording van bedrijfsgeneeskundige vragen rondom zwangerschap volgens de principes van evidence-based medicine.
• Een overzicht van beschikbare informatie en bronnen over zwangerschap en werk.

Artikel van van Beukering MDM

• Recente cijfers tonen een dalende trend in het aantal WAO-uitkeringen vanwege zwangerschap en bevalling. Belangrijkste oorzaak van deze daling is waarschijnlijk het feit dat het verlof meestal niet meer meetelt in de periode voor de WAO of WAI.
• De Nederlandse uitkering bij zwangerschaps- en bevallingsverlof behoort tot de Europese middenmoot, echter met 16 weken is het Nederlandse verlof één van de kortste in Europa.
• Er is geen bescherming ten aanzien van de risico's in het begin van de zwangerschap, voordat de vrouw haar zwangerschap heeft gemeld.
• Er wordt te weinig gebruik gemaakt van de regelgeving rondom reproductierisico's en verzuim tijdens de zwangerschap. De meeste werkgevers blijken niet goed op de hoogte van regelgeving rond zwangerschap en bevalling. Daarnaast is het de vraag of werkgevers wel alle regels willen weten en toepassen.

Interessante referenties: van Beukering, 2002 / Saurel-Cubizolles et al., 2004 / Saurel-Cubizolles et al., 1997 / Taskinen et al., 1995 / Mercer onderzoek naar zwangerschapsverlof en uitkeringen in Europa (mei 2006)

Artikel van Brand T, Stinis HPJ

2 casussen

1. Kleuterleidster in kinderdagverblijf (geen antistoffen tegen Parvovirus-B19)
2. Kinderwens en werken met reproductietoxische stoffen in een laboratorium

• Zwangere in kinderdagverblijf vraagt kennis van zaken.
• Parvo-B19: ook als het misgaat niet altijd alles verloren.
• Toxische stoffen en zwangerschap: multidisciplinaire benadering.

Sources:
http://www.amc.nl/upload/teksten/coronel%20instituut/2006_Schaafsma_Zoeken%20en%20vinden%20van%20informatie%20over.pdf.pdf

The influence of occupational exposures on male reproductive function

Occupational Medicine 2006; 56: 544-553.
Jensen Tina Kold, Bonde Jens Peter and Joffe Michael

Many studies have found a decrease in semen quality which has increase the focus on male reproductive health.

Welding and Metals

New evidence suggest that metal welding is not as damaging to male reproduction as previously suggested, probably because the exposure levels in the Western world has decreased.
Some specialized workers may however still perform tasks (e.g. stainless steel welding) which may damage their reproduction.

Rachootin et al. / Mortensen / Bonde / Jelnes et al. / Ernst / Ernst et al. / Bonde et al. / Bonde / Bonde et al. / Hjollund et al. / Hjollund et al. / Hjollund et al. / Bonde / Hjollund et al. / Hjollund et al.

Inorganic lead

The male reproductive toxicity of lead has been known for a long time.

There is evidence of an adverse effect of inorganic lead on male reproduction and fecundity.

Other metals

Several studies in rats and mice have demonstrated testicular toxicity of a number of other metals including cadmium, mercury, boron, manganese, and hexavalent chromium but human data are sparse.

Alexander et al. / Wildt et al. / Assennato et al. / Lancranjan et al. / Viskum et al. / Robbins et al. / Bonde et al. / Apostoli et al. / Joffe et al. / Shiau et al. / Benoff et al. / Bonde / Hubbard

Physical exposures

Heat and sedentary body posture

It is well known that internal heating (fever) and external heating for short period of time may result in a dramatic but temporary decrease of sperm count and other aspects of semen quality after a delay of some 6-8 weeks.

Studies among bakers, ceramics workers, foundry workers have indicated reduced sperm counts (Review by Thonneau et al., 1998).

Semen characteristics in specialized welders declined significantly (Bonde, 1993)

Sedentary work position is associated with an increased scrotal temperature.
Taxi drivers in Rome: decreased number of morphological normal sperms (Figa-Talamanca et al., 1996).
Effect of sedentary work needs to be further explored.

Radiation

Testicular tissue is highly sensitive to ionizing radiation.
0.15 Gy may temporarily reduce sperm counts, 2 Gy may result in longlasting or permanent azoospermia.

Rowley et al., 1974

An occupational exposure limit of 15 mSv/year has been adopted in several countries.

Chemical exposures

Solvents

Availabe data suggest that a number of solvents used in industries can affect male reproductive function (glycol ethers (2-EE, 2-ME), 2-bromopropane, carbon disulphide), while the evidence for others is more limited.

Welch et al. / Figa-Talamanca et al. / Veulemans et al. / Lancranjan et al/ Lancranjan et al. / Cirla et al. / Meyer / Wagar et al. / Vanhoorne et al. / Vanhoorne et al. / Jelnes / Kolstad et al. / Eskenazi et al. / Eskenazi et al/ Tola et al. /Rasmussen et al. /Chia et al. / Kim et al. / Liu et al.

Pesticides

A few studies indicate that persistant organochlorine pollutants interfere with sperm motility and sperm DNA integrity

Goldsmith et al. / Potashnik et al. / Sandifer et al. / Ratcliffe et al. / Wong et al. / Zober et al. / Whorton et al. / Wyrobek et al. / Taylor / Taylor / Guzelian / Cannon et al. / Swan et al. / de Cock et al. / Abell et al. / Abell et al. / Abell et al. / Jensen et al. / Larsen et al. / Larsen et al. / Spano et al. / Toft et al.

Psychological exposures

Occupational stress and burn-out have been related to male infertility and reduced semen quality (Sheiner et al., 2002 & Clarke et al., 1999).

Effect of psychological stress on semen quality and male reproductive health is currently not determined.

Hjollund et al., 2004 (job strain)
Hjollund et al., 2004 (male psychologic stress)

Conclusions and recommendations:

Several occupational and environmental exposures and toxins have known or suspected deleterious actions to male reproductive function.

The evidence is strongly supported in well-designed epidemiological studies for heat, ionizing radiation, inorganic lead, DBCP, EDB, some ethylene glycol ethers, carbon disulfide and welding operations.

For other agents the association is only suspected or suggested and needs further evaluation before conclusions can be drawn.

Maternal occupational exposures and risk of specific birth defects

Occupational Medicine 2006; 56: 532-543.

Thulstrup Ane Marie and Bonde Jens Peter

Five specific birth defects were identified:

1. Neural tube defects
2. Cleft lip and cleft palate
3. Congenital heart defects
4. Urinary tract defects
5. Limb defects

Birth defects or congenital malformations (at time of birth): 3,5% of all live births.

Data on spontaneous abortion may be important for the detection of teratogenic factors.

In nearly 70% of all birth defects, there is still no known risk factor.

Close to 30% of all pregnancies end in a foetal loss or spontaneous abortion.

Neural tube defects

Prevalence in Europe +/- 1 per 1000 births

Protective factor: Folic acid intake

Non-occupational risk factor: hight vitamin A (retinol) intake

Occupational risk: 10 studies (2 cohort & 8 case-control studies)

Possible risks among women working in health care, agriculture and cleaning.

Risk seems to be following exposure to glycol ethers or lead

Caution: Limited evidence !!!

Holmberg et al. / Ericson et al. / Matte et al. / Bianchi et al. / Cordier et al. / Blatter et al. / Lin et al. / Irgens et al. / Blaasaas et al. / Brender et al.

Cleft lip and Cleft palate

Prevalence in Europe:

+/- 1.5 per 1000 births for cleft lip

+/- 0.8 per 1000 births for cleft palate

Well accepted that genetic factors contribute to the aetiology

Protective factor: folic acid intake

Non-occupational risk factors: Maternal smoking - High vitamin A intake

Occupational risk: 11 studies (2 registry-based & 9 case-control studies)

Employment during pregnancy in the leather industry or as a hairdresser has been suggested to be associated with increased risk of cleft lip or cleft palate.

Exposures like organic solvents, glycol ethers and pesticides have been suggested in a number of studies.

Caution: Limited evidence !!!

Holmberg et al. / Matte et al. / Nurminen / Bianchi et al. / Cordier et al. / Lin et al. / Lorente et al. / Blaasaas et al. / Shaw et al. / Carmichael et al. / Chia et al.

Heart abnormality

Prevalence is +/- 4-6 per 1000 births

Prevalence increased simultaneously with the increasing survival of premature infants.

Possible non-occupational risk factors: alcohol consumption during first trimester, maternal diabetes mellitus, high body mass index & use of antiepileptics

Occupational risk: 7 studies (2 registry-based & 5 case-control studies)

Evidence is inconclusive !!!

Tikkanen et al. / Matte et al. / Bianchi et al. / Cordier et al. / Cedergren et al. / Carmichael et al. / Chia et al.

Urogenital abnormality

Prevalence of hypospadias: 2-4 per 1000 births

Prevalence of cryptorchidism: <>

Genetic defects play a role in hypospadias

Occupational risk factors: 8 case-control studies

Few studies do not allow any conclusions on occupational risk for cryptorchidism or for hypospadias !!!

Bianchi et al. / Cordier et al. / Garcia / Matte et al. /Weidner et al. / Vrijheid et al. / Pierik et al.

Limb defects

Prevalence: +/- 0.5-1% per 1000 births

Genetic interaction of teratogenic effects of smoking ?

Non-occupational risk factors: Maternal smoking

Occupational risk: 6 studies

Limited number of studies focusing on limb defects are insufficient to assess the risk !!!

Bianchi et al. / Cordier et al. / Garcia / Matte et al. / Weidner et al. / Vrijheid et al. / Pierik et al.

Discussion & Remarks:

Original literature does not provide clear evidence for causal associations between maternal occupational exposures and specific birth defects.

It seems that little progress has been made since Sever published a review (1994).

There is a strong interaction between age, lifestyle factors (smoking, alcohol, social class, nutrition) and occupational exposures during pregnancy, which complicates the proper interpretation of associations.

Final conclusions:

Epidemiological research has not convincingly demonstrated any workplace exposure as a specific teratogen but sevral concerns implying possible teratogenic effects of volatile organic solvents, glycol ethers, some pesticides and some heavy metals call for additional research.

It seems to be difficult or impossible to establish exposure-response relationships. Such studies will probably require very large source populations and call for international research cooperation.

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)

Solvents

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)

Pesticides

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

Radiation

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

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

Conclusions:

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.

Effects of occupational exposure on the reproductive system: core evidence and practical implications

Occupational Medicine 2006; 56: 516-520.
Burdorf Alex, Figa-Talamanca Irene, Jensen Tina Kold and Thulstrup Ane Marie

Key messages:

• The reproductive system of both women and men can be affected by occupational exposure and for most health effects both maternal and paternal exposure may be a relevant route.
• The interpretation of an association between an occupational exposure and a reproductive health effect is almost always hampered by the fact that many adverse outcomes may be caused by multiple (work-related) factors, making it extremely difficult ot attribute a particular outcome to a specific occupational exposure.
• Occupational exposure may only be relevant during specific time windows, for example shortly before conception or during early pregnancy.

Summary of the core findings:

Physical factors

Ionizing radiation: Spontaneous abortion - Congenital defects - Reduced sperm count / Azoospermia

Noise (> 90 dB(A)): Spontaneous abortion / Low birth weight / Pre-term birth

Heat: Reduced sperm count

Chemical agents

Lead: Low birth weight - Neural tube defects - Reduced sperm count

Mercury: Spontaneous abortion

Organic solvents: Spontaneous abortion

Tetrachloroethylene: Spontaneous abortion - Cleft lip/palate

Glycol ethers: Spontaneous abortion - Reduced semen quality

Dibromopropane: Menstrual disturbances / Spontaneous abortion - Neural tube defects - Reduced semen quality

Ethylene oxide: Pre-term birth / Spontaneous abortion - Cleft lip/palate

Anaesthetic gases: Spontaneous abortion

Antineoplastic drugs: Spontaneous abortion

Pesticides: Reduced sperm count / Azoospermia

Ethylenedibromide: Neural tube defects / Cleft lip/palate - Reduced sperm count / Azoospermia

Carbon disulfide: Reduced quantity and quality of semen

Specific types of welding: Reduced quantity and quality of semen

Psychosocial factors

Irregular work hours: Spontaneous abortion / Menstrual disturbances

Stress: Spontaneous abortion / Pre-term birth

Physical load

Heavy physical work (high energy expenditure): Spontaneous abortion / Low birth weight

Frequent heavy lifting: Pre-term birth / Spontaneous abortion

Prolonged standing: Low birth weight / Pre-term birth / Spontaneous abortion

Both maternal and paternal occupational exposures to ionizing radiation and heat have been established as risk factors for fertility problems.

Limitations in interpretation:

Many uncertainties still exist as to the interpretation of the evidence presented.

A core issue is, undoubtedly, the exposure assessment in epidemiological studies.
In most studies: self-reported job titles (questionnaires)
This assessment strategy is far too crude to establish a meaningful insight into the magnitude and duration of the specific exposure responsible for the observed health effect.

Some occupations have been consistently associated with reproductive effects (e.g. hairdressers, greenhouse workers), but is remains difficult to identify the specific risk factor since in most workplaces these workers are exposed to a mixture of different risk factors and different chemical compounds.
This severly limits the evaluation of the exposure-response relationship for single risk factors.

It is well-established that maternal exposure in the few months before conception is important for fertility and that teratogenic effects may arise during the organogenesis phase during the first 3-8 weeks of pregnancy.
However, long-term exposure may also be relevant for example germ line DNA modifications, or where the agents are biopersistent and accumulate in body fate, such as several pesticides.

Appropriate time windows of highest susceptibility are not well-established for most occupational hazards, which hampers clear advice as to when preventive measures should be undertaken.

A specific feature of reproductive health is that the causal pathway of hazardous exposure in occupations may be female- or male-mediated.

There is extensive evidence from animal studies for male-mediated developmental effects (e.g. spontaneous abortions, growth retardation, malformations, behavioural abnormalities) of environmental agents .

Occupational exposures are generally lower today than they were years or decades ago. Changes in the production process and control measures have had a noticeable impact on exposure levels. In addition, toxic substances may have been replaced by less toxic agents (e.g. PER partly replaced by TCE).
One has to bear in mind that industries may have outsourced the most dirty jobs towards less developed countries or less well-protected small enterprises.

In conclusion, the available evidence presented in this issue of Occupational Medicine, does not allow to derive clear exposure-response relationships.
It remains difficult to arrive at sound conclusions as to the amount of exposure that will require control measures to prevent the occurence of adverse effects on the reproductive system.

Practival implications for occupational health:

The occupational health professional is faced with difficult questions regarding the necessary measures to be taken to ensure that health effects on the reproductive system will not occur.

In general, the precautions to be taken for the protection of the reproductive health of both women and men will not differ form the safeguarding of all workers.

European Union - European Directive 92/85/EEC

Detailed guidelines on the requirements with respect to physical, chemical and biological agents, and industrial conditions including physical load, mental and physical fatigue, and physical and mental stress.

Conclusions:

The evidence on occupational risk factors for adverse effects on the reproductive system is consistent for a limited number of risk factors, most notably exposure to lead, glycol ethers, organic solvents, pesticides and ionizing radiation.

It remains difficult to arrive at sound conclusions on the level of exposure and the specific chemicals within the groups of glycol ethers, organic solvents and pesticides that are associated with an increased risk.

Precautions to be taken for the protection of the reproductive health of both women and men have traditionally focused on pregnant women in the workplace.

The available evidence strongly suggests that exposure in the few months before conception may be of importance too, both among women and men.

Occupational Medicine 2006 In-depth reviews on Reproduction & Work

Occupational Medicine 2006; 56: 516-553.
In-depth review on Occupation and Reproduction.
4 articles:

1. Burdorf Alex, Irene Figa-Talamanca, Tina Kold Jensen and Ane Marie Thulstrup. Effects of occupational exposure on the reproductive system: core evidence and practical implications. pp 516-520.
2. Irene Figa-Talamanca. Occupational risk factors and reproductive health of women. pp 521-531.
3. Ane Marie Thulstrup and Jens Peter Bonde. Maternal occupational exposure and risk of specific birth defects. pp 532-543.
4. Tina Kold Jensen, Jens Peter Bonde and Michael Joffe. The influence of occupational exposure on male reproductive function. pp 544-553.

Occupations at risk - Risky exposures for maternity - Reproductive Risks

In the future, I hope to publish a risk analysis for specific occupations, and for specific occupational exposures, like certain tasks, products or agents.

You are kindly invited to participate in this blog.

Please contact me with relevant information (websites or scientific publications) not found on this blog.
My address:
Dokter Wim Van Hooste, MD
Preventieadviseur-Arbeidsgeneesheer, Occupational Health Physician
Stekenestraat 27
B-9190 Stekene
Belgium
@: wimvanhooste(a)skynet.be