Table 1 Effect of Environmental Factors on Semen Quality and Male Fertility: A Comparison of Human and Animal Studies
From: Impact of environmental factors on human semen quality and male fertility: a narrative review
S. no | Predisposing factor | Source/cause | Human studies | Animal studies |
|---|---|---|---|---|
1 | Air Pollution | Motor vehicles exhaust, factories, fire, household, agriculture, waste treatment, oil refineries, natural sources, such as volcanic eruptions, wind, etc. | PM2.5 in the air is directly associated with total sperm number and concentration [25, 128] PM10 is related to semen volume and typical forms and inversely related to atypical forms [25, 129] SO2 exposure at the time of sperm development causes oxidative damage to sperm [5] Air pollution negatively affects testosterone levels [129] | PM2.5 exposure in mice causes a significant fall in sperm concentration, motility, serum testosterone levels, an increased percentage of morphological abnormalities in sperms [130] •PM2.5 causes severe testicular damage on histopathology [131] |
2 | Chemicals | |||
i. Dioxins/Furans | Produced as a by-product of industrial and natural processes, such as smelting, chlorine bleaching of paper and pulp, production of pesticides, biomedical and plastic waste incineration | Reduced sperm concentration and motility [47] Ejaculate of infertile men had 2.2–2.3 times higher content of dioxins and furans as compared to their fertile counterparts [49] | Reduced daily sperm production, epididymis sperm counts, and dose-dependent histological changes in the testes [132] Fall in plasma concentrations of testosterone, and LH [132] | |
ii. Bisphenol A (BPA) | A major component of plastic and released during production, use, or disposal of plastics and break-down of industrial plastic-related wastes | Pro-oxidative/apoptotic mitochondrial dysfunction [56] Inverse correlation between sperm concentration and urinary BPA levels [67] | Reduced sperm production, motility, increased sperm abnormalities, acrosomal and sperm plasma membrane damage, decreased mitochondrial activity and, increased defective spermatozoa [58, 133] Reduced serum concentrations of testosterone, LH [58] | |
iii. Pesticides/ Herbicides | Used in agriculture, to control insects | Reduced sperm motility, sperm count, concentration, and increased sperm morphological abnormalities [134, 135] | Reduced sperm motility, motion kinematic parameters, sperm ATP levels, and increased morphological modifications [136, 137] | |
iv. Phthalates | Found in numerous consumer products, such as toys, pharmaceuticals, cosmetic products, building and construction materials, scent retainers, some medications, and personal care products | Reduced total sperm counts, sperm concentration, larger sperm head sizes, an increased number of morphologically abnormal sperm lead to reduced semen quality [86, 87] | Reduced sperm motility, capacitation, and acrosome reaction, leading to poor fertilization in mice [138] Increased DNA fragmentation and decreased sperm motility in dogs [139] | |
v. Heavy Metals | Volcanic eruptions, Weathering of metal-bearing rocks, mining, and industrial and agricultural activities | Increased blood Cadmium and Barium levels and higher seminal lead, Cadmium, Barium, and Uranium result in low sperm viability and increased immotile sperm [94, 96] Uranium levels correlate with decreased sperm motility and abnormal sperm morphology [94] Exposure to high CuSO4 (250 µg/ml) and CdCl2 (500 µg/ml) results in reduced sperm motility [97] | Acute and chronic cadmium exposure causes reduced sperm motility, viability, and acrosome reaction both in vivo and in vitro [140] Heavy metals adversely affect testicular morphology, sperm production, and quality [141] | |
3 | Heat Exposure | Occupational exposure in people working in furnaces, bakeries, welding, ceramic factories, laundries, dry cleaning shops, or drivers, hot climate, excessive use of hot tubs, Jacuzzi, or hot baths | Extremes of temperature result in decreased semen quality including reduced sperm concentration, total sperm count, total motility, progressive motility [120] Reduced sperm concentration and total amount per ejaculate in summers as compared to winters [121] | Heat stress causes a rise in sperm abnormalities, lipid peroxidation, altered mitochondrial function, decreased sperm motility, plasma membrane integrity, increased DNA fragmentation, and reduced sperm quality [118, 142, 143] Heatwave conditions (5–7 °C above the optimum temperature for 5 days) adversely affect male reproductive potential, halve male fertility, and severely affect sperm competitive ability [144] |