Table 3 Papers assessing the impact of occupational factors on reproductive and infertility indices

Occupational factors

lepecka-Klusek et al. (2011) [81]

Prospective

Questionnaire - physical Examination - measurement

224 males (Poland)

Living conditions, occupational hazards, and difficult tasks were not associated with semen quality.

Minguez-Alarcon et al. (2017) [82]

Prospective cohort

Questionnaire- measurement

(n=473 and n=313 for ovarian reserve and ovarian response analysis, respectively) USA

Women who moved heavy objects and worked longer every day had fewer oocytes (p value=0.08) mature oocytes (p value=0.007) and antral follicles (p value=0.06) than others. Consequently, occupational factors such as heavy physical activity may be associated with decreased fertility.

Gaskins et al. (2015) [83]

Cohort

Questionnaire

1739 women (USA)

Women, who worked more than 40 hours a week (95% CI 7 to 35%) or moved heavy objects, became pregnant later than those who worked 21 to 40 h per week. (p trend=0.005).

Wang et al. (2015) [84]

Cross-sectional

Questionnaire, physical examination, measurement

Exposed group (N=114)

Non-exposed group (N=76)

(China)

There was no significant difference in semen volume, sperm concentration, and total count in both groups (a group exposed to formaldehyde (FA) and a control group) but a number of motile sperm in the group exposed to formaldehyde was lower than the control group. (OR=3.21; 95%CI 1.24–8.28).

A significant elevated risk of abnormal sperm progressive motility was found in the low-FA-exposed group (OR= 2.58; 95%CI 1.11–5.97) and high-FA-exposed group (OR= 3.41; 95%CI 1.45–7.92, respectively) compared with the reference group.

Wijesekara et al. (2015) [85]

Cross-sectional

Questionnaire, measurement

300 men (Colombo- Sri Lanka)

People in polluted regions and exposed to industrial chemicals had higher percentages of lead and cadmium in seminal plasma Pb (r=0.06, p>0.05) and Cd (r=0.26, p<0.05) and less alive, motile, and normal sperms. In the exposed, mean lead concentration was 17.7 (95% CI 15.0–20.4) μg/dl and 13.5 (95% CI 11.2–15.7) μg/dl in non-exposed and cadmium concentration in exposed was 1.2 (95% CI 1.1–1.4) μg/dl and 1.1 (0.9–1.3) μg/dl in non-exposed.

de Fleurian et al. (2009) [86]

Cross-sectional

Interview, questionnaire, measurement

Total (n = 402) Exposed group (n = 314)

Non-exposed group (n = 88) (France)

Various physical and chemical occupational factors, including mechanical vibration, heat, prolonged sitting, exposure to chemicals, and heavy metals can affect semen quality. (adjusted odds ratio [OR] = 5.4; 95% confidence interval [CI], 1.6–18.1) solvents (OR = 2.5; 95% CI, 1.4–4.4) fumes (OR = 1.9; 95% CI, 1.1–3.4), and polycyclic aromatic hydrocarbons (OR = 1.9; 95% CI, 1.1–3.5). Exposure to pesticides or cement was nearly significant (OR = 3.6; 95% CI, 0.8–15.8, and OR = 2.5; 95% CI, 0.95–6.5, respectively) (mechanical vibration was associated with oligospermia and teratospermia, exposure to high temperature; and prolonged sitting was associated with lower mobility) but exposure to ionizing radiation and electromagnetic fields was not associated with lower semen quality.

Daoud et al. (2017) [87]

Cross-sectional

Questionnaire, measurement

2122 men (Sfax, Tunisia)

Occupational exposure to pesticides and substances such as cement was correlated with asthenozoospermia, necrozoospermia, and oligozoospermia. pesticides: (adjusted odds ratio [OR] = 1.6; 95% CI, 1.0–2.4) and necrozoospermia (OR = 2.6; 95% CI, 1.4–4.7). Cement: (OR = 1.1; 95% CI, 0.9–1.4). While there was no relationship between the presence in very hot environments and mechanical vibrations with sperm abnormalities.

Mahboubi et al. (2014) [88]

Case-control

Questionnaire, measurement

Infertile men (n: 108)

Fertile men (n: 161)

(Shiraz, Iran)

Workers with heavy physical activity are more prone to infertility due to damage to testicles and a decrease in semen quality. Smoking is also associated with decreased sperm motility.

Kumar et al. (2013) [89]

Cross-sectional

Questionnaire, measurement

134 males ((‘unexposed’ group, n=51), (‘exposed’ group, n=83)) (India)

Occupational exposure to ionizing radiation is associated with decreased motility and normal morphology of sperm by the creation of malformations and mutations in sperm DNA (P<0.05–0.0001) but further studies should be conducted to investigate fertility.

Jeng et al. (2016) [90]

Cross-sectional

Questionnaire, measurement

(Nonexposed’ group N=35

Exposed group (N= 52) (Taiwan)

Coal furnace workers experienced a greater reduction in sperm motility and normal morphology than the control group, but it was not statistically significant. For DNA integrity, the coke oven workers had significantly higher concentrations of bulky DNA adducts and 8-oxo-7,8-dihydro-2’-deoxyguanosine than the control subjects (p = 0.009 and p = 0.048, respectively)

The workers’ occupational exposure to aromatic hydrocarbons endangers the reproductive health by damaging the sperm DNA and decreasing its integrity.

Kim et al. (2016) [91]

Meta-analysis

electronic databases

19 articles

The meta-analysis revealed a significantly increased risk of infertility (OR 1.15, 95 % CI 1.03–1.28), fetal death (OR 1.14, 95 % CI 1.04–1.24), and preterm delivery (OR 1.04, 95 % CI 1.00– 1.07) among hairdressers and cosmetologists.