Decline in semen quality and reproduction has been attributed to changing lifestyle and pollution. However, there have been contradictory reports during the past 50 years.
Studies have shown that constant genetic and evolutionary pressure has led to a decline in spermatogenesis. Semen quality decline in Paris, Italy, Denmark, Norway, Scotland, Belgium, Finland, India and USA has been related to increasing pollutants and industrialization.
Possible causes for semen quality decline are pollution due to physical (heat, radiation) and chemical (halogens, glycols/glycol ethers, disinfectants, organophosphates, pesticides, insecticides, organic solvents, carbon disulphide, dibromochloropropane; heavy metals like lead, cadmium, chromium, mercury, beryllium, manganese, zinc; phytoestrogens/ estrogenic/ androgenic/ hormonal compounds; smoke, automobile/ industrial emissions, nuclear dust, contraceptive residues) factors present in general environment and occupational areas.
Smoking, obesity, excessive heat to testicles, drinking excess alcohol and caffeinated beverages, eating estrogenic/androgenic foods have been reported to affect male fertility adversely.
Prolonged cell phone usage affects sperm motility. Increased sperm abnormalities and reduced sperm motility have been seen in metal welders.
Semen quality (motility, count, normal sperms) and fecundity decrements were also related to stress, working duration and occupational posture.
All above factors induce oxidative and DNA damage, teratogenecity, congenital defects, endocrine disruption, abortion, still birth, anatomic, genetic, immunological disturbances etc affecting semen quality and reproduction.
However, due to contradictions and non replications in various epidemiological findings (due to methodological problems), a wide integrated study with various parameters should be undertaken to address the issue.
According to National Health Survey reports the level of infertility in India is 2.5 % at national level and varies from 1.4 to 4.4 % among different states of India and Karnataka as per our statistics is 3.1%. In India alone, 18 million couples suffer from infertility which accounts for 14 % of all infertile couples in the world. The global magnitude of infertility is 60 to 80 million couples suffer infertility each year.
Semen quality
The meta-analysis report of Carlsen et al. (1992) that semen quality in men worldwide has undergone a decline. Decrease in semen quality has also been reported from different geographical regions like Paris (Auger et al., 1995), Italy (Bilotta et al., 1999), Denmark (Bostofte et al., 1983; Jorgensen et al., 2006), Norway (Bendvold, 1989), Scotland (Irvine et al., 1998), Belgium (Van Waeleghem et al., 1996), Finland (Horte et al., 2001) and USA (Leto and Frensilli, 1981; Swan et al., 2003).Published information in Asia is limited. Zhang et al. (1999) analysed the change in sperm quality and male infertility among men in China from 1983 to 1996. The results of the analysis showed a definite negative correlation and statistical significant decrease in sperm concentration, motility and morphology.
Sperm quality in men attending our clinic shows a 15 % decline in sperm motility and 2 % decline in morphology over the last 5 years.
Air pollution
Air, water and soil pollutants are commonly known as environmental endocrine disruptors or xenoestrogens or environmental hormones. Disrupting chemicals like alkylmercury, carbon disulphide, vinclozolin, procymidone, pesticides, insecticides, plastics, gums, paints, glycols, glycolethers and glycolesters.
Air pollution is mainly caused by smoke resulting from automobiles, industrial gases and domestic cooking using wood, cow-dung cake which increases the levels of lead, carbon monoxide, sulphur, nitrogen oxide, fluorides etc. and thus influence the male reproductive health.
Comparison of semen quality revealed decrease in sperm motility, normal sperm numbers, decreased normal head shape but increased abnormal chromatin sperms in higher air pollution period. Air pollution also increases DNA damage in human especially in susceptible groups. Intermittent exposure to environmental pollution results in sperm DNA damage causing male infertility and miscarriage.
In a study in Italy people who were exposed to traffic fumes had poorer sperm quality and in particular, had lower sperm motility.
Ozone exposure is known to cause oxidative stress, which is documented to disrupt testicular and sperm function.
As with smoking, exposure to ozone may induce either an inflammatory reaction in the male genital tract or the formation of circulating toxic species and, thus can cause a decline in sperm concentration.
Besides ozone, nitrogen oxide, carbon monoxide and fine particulate matter, each of these air pollutants was believed to be capable of impacting sperm production.
Heavy metals
Heavy metals affect male reproduction causing various lesions in reproductive organs leading to infertility. Cadmium is a ubiquitous heavy trace metal toxicant and is well known as an industrial pollutant. Exposures to cadmium have been reported to reduce male fertility.
Chromium is an important heavy metal which possesses several industrial applications Occupational exposure to chromium leads to alteration of semen status and may adversely affect the reproductive success of exposed workers.
Lead is the most significant toxin of the heavy metals. Industrial decisions, such as the addition of lead to paints, dyes, and gasoline, have created an epidemic of lead poisonings. Lead is a naturally occurring substance and can be found in organic and inorganic forms.
Lead is a reproductive toxicant detrimental to human semen quality. Decreased sperm count, motility, acid phosphatase, succinic dehydrogenase, fructose, surface reaction of sperm head DNA besides increasing abnormal sperms was reported in occupational exposure of lead in printing press workers in India. Higher lead level lowers sperm’s ability to bind and fertilize the egg.
Mercury, widely used in modern technology and industrial revolution, has become an important pollutant for animals and humans. Mercury intoxication has been associated with male reproductive toxicity in experimental animals and mercury may have the potential to produce adverse effects on fertility of men. In a small population in India, it was found that occupational exposure to metals, solvents, pesticides, extreme heat or vapours increases incidence of poor motility (oligo-asthenospermia) and even zero sperms (azoospermia).
Changing lifestyle
There is a good evidence that diet and lifestyle can impair a man’s fertility. Several studies have clearly shown that cigarette smoking lowers both sperm counts and sperm motility. Excessive alcohol consumption has also been shown to impair normal. It is well known that the testicles should be cooler than the rest of the body for sperm production to be at its best. The harmful effect of a varicocele on sperm production is believed to result from the extra warming of the area caused by the dilated veins.
Hormone-like substances such as DHEA or “androgens” intended to build muscle mass can actually stop sperm production completely. Excessive consumption of coffee or other caffeine-containing beverages have been reported to be deleterious for sperm production. It is probably best to avoid high intake of soy products, since they can contain weak plant estrogens. Moderate exercise may be beneficial. However, prolonged, excessive and no exercise may be bad.
Oxidative stress is a common factor in some male and female infertility. This is due to certain molecules known as “reactive oxygen species” or oxidants in the semen which can damage the sperm cell membrane, DNA and fertility.
Prolonged cell phone usage may negatively affected sperm motility characteristics, though still needs to be validated.
It is still not clear whether the psychological strain in normal jobs affects male reproductive function or sperm counts. However, stress has some effect on ability to conceive in men with already low sperm concentration.
Occupational hazards
However men working in hot environment like welders had reduced progressive motility, increased sperm defects like coiled tails. Job stress also affects sperm motility and morphology causing abnormal heads and coiled tail. Prolonged occupational heat, radiation, chemical exposures were found to affect spermatogenesis.
General environmental pollution
There is an unexplained three fold increase in US male infertility (sperm density, semen volume) between 1965-82 was due to environmental /occupational pollution (with increasing toxic substances, halogenic compounds, glycols and glycol ethers, metals, hormones), abnormal lifestyle, heat, smoking, consumption of alcohol and drugs etc. affecting sperm production.
Radiation
Radiation causes degenerative changes in germ cell affecting steroid synthesis. It also causes genetic damages in germ cell like gene mutations, chromosomal aberrations, spermatogonial apoptosis and sterility.
Fluoride
Fluorine and fluoridesoccur only in the form of compounds with other elements. It is used in small amounts to purify water and to decrease tooth decay. Fluoride toxicity may cause adverse effects on the reproductive system of males living in fluorosis endemic areas.
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