Exposure to environmental toxins and its relationship with human semen quality: A case-control study

Background. Several studies have suggested that human semen quality has declined during the last decades. Semen quality may be declining due to environmental pollutants, occupational or changes in lifestyle, like dietary habits, but we know less of the impact of those factors on male fertility.;Methods. This is a case-control study of 30 males with poor semen quality and 31 normozoospermic males as controls attending a fertility clinic. We concluded different tests to patients to be sure that their seminal impairs was not a result of endocrine or genetic problems. Two main studies were carried out. The first study was in relationship with usual food intakes. Food frequency questionnaire was designed in 5 blocks, each one of them addressing a general group of items: (1) Dairy products, (2) eggs, red and pork meat, chicken, cold meats, sausages, organs, fish and shellfish, (3) raw or cooked vegetables, potatoes, legumes and fruits, (4) vegetable oils and cakes, (5) alcoholic and non-alcoholic drinks. Frequency of food consumption was registered in a scale with 9 values ranging from no consumption to repeated daily consumption. In the second study we recorded occupational exposures to toxics and chemicals using a questionnaire adapted to meet specific study objectives. Specific environmental occupational exposures recorded included metals, acids, bases or alcohols; pesticides or insecticides; glues, solvents or silicones; gasoline, exhaust fumes; paintings or dyes; dust particles, fibres, physical agents, fuel-oil or greases and welding fumes or gases. We registered current occupation, daily activities, working history, and current and past occupational exposures. Information on environmental and lifestyle characteristics were also recorded (toxic habits, hobbies). Mean values of food frequencies and lifetime exposure to toxics were compared using non-parametric methods (U Mann-Whitney). Odds ratios, with 95% confidence intervals, were used to explore differences in lifestyle or other occupational exposures. Significance level for all tests was set at p≤0.05.;Results. Infertile males had a higher intake of yogurt, meat products and potatoes (p value ≤ 0.05). Control group had a higher food intake of skimmed milk, shellfish and some raw vegetables (lettuce and tomatoes), and some fruits (apricots and peaches) and sweets (p value ≤ 0.01). Other food items did not show statistically significant differences between the two groups. In the occupational exposure study we found that more than two thirds of the cases (23/30), as compared with less than one third of controls (10/31) had been exposed occupationally to at least one toxic or pollutant (OR=6.9; 95% CI: 2.2-21.4) and were also exposed to them currently (OR=5.2; 95% CI: 1.6-17.2). Exposure to glues, solvents or silicones (OR=22.9; 95% CI: 2.8-190.9), metals (OR=8.8; 95% CI: 1.4-54.2) and physical agents (OR=7.3; 95% CI: 1.4-36.7) in the past, as well as current exposure to glues, solvents or silicones and physical agents, were significantly higher in infertile males than in controls. Infertile males had significantly higher lifetime exposure to overall toxics and pollutants, to metals, and to glues, solvents or silicones (p-values ≤ 0.05). Infertile males were more likely to be occupied in industrial activities (shoe and leather industry, shipyard workers, welders, plumbers or other industries) and significantly less frequently occupied as while collar professionals or clerical workers.;Conclusions. Food intake may influence semen quality in humans, with some foods, like certain meat or dairy products showing a deleterious effect, possibly connected to a higher exposure to xenobiotics, and fruits and vegetables having a protective one. Male infertility in patients attending fertility clinics may be largely the result of occupational exposures, at least in our setting, mainly in industrial workers exposed to toxics and chemicals (solvents, glues, metals) or extreme physical agents (heat, cold). More research is needed to better understand the mechanisms, effects and interactions of dietary habits and chemical occupational exposures on male infertility and its reproductive systems.