Fertile And Infertile Males For Mercury example essay topic

Biology 108 - Assignment 1 "Human fertility is declining because of pollution" I believe that human fertility is declining due to pollution. To study this question we need to look at infertility in humans. Infertility can be defined as "the inability to conceive, carry, or deliver a healthy child" (Funk & Wagnall, 1986). This may be caused by gene mutation, lowered sperm counts, impairment of sperm motility or many other reasons. We also know that "due to a higher surface area to volume ratio, sperm are usually more sensitive to toxicant exposure than eggs" (Pagano, 1995). Many environmental factors can affect infertility in humans and mammals; the three major groups are heavy metals, industrial pollutants and pesticides / fungicides.

Dr. H.J. Muller studied the affect of different forms of radiation that caused gene mutations which in turn caused infertility. Muller exposed male fruit flies to different amounts of X radiation and he found that the X-chromosomes in the in the flies mutated and that given a high enough does of X radiation the fruit flies became sterile. Muller made numerous studies of various effects radiation has on genes and his research proved that "any high-energy radiation- radium, cosmic rays, the gamma rays of radioactive elements, even ultra violet light- will cause mutations" (Cook, 1951) thus leaving the flies in this case sterile with the correct measured dosage. Muller also researched the effects of radiation through different generations and he noted that a symptom of this poisoning would be "lethal gene sterility which kills the embryo. Many more couples would have no -or fewer- children. Among these born, there would be a slow increase in genetic defects due to radiation- induced mutations.

There would be a decline in vigor, vitality and fertility". (Cook, 1951) Muller also noted that if the radiation continued for a considerable time humans both male and female could become sterile. The Center for Coastal Pollution and Conservation from the City University of Hong Kong did a study on the impairment of sea urchin sperm quality by UV-B radiation. They examined the effects of environmentally realistic levels of UV-B radiation on sperm mortality, and the fertilization capabilities for the short spine sea urchin. They found at the end of their study that there was an significant decline in the percentage of motile sperm, and their was also a significant decline in fertilization after being exposed to the UV- B radiation. After the completion of their study they also found that exposure to UV -A had the same adverse affects as UV-B. They also discovered that UV-C might also lead to infertility.

After an exposure to UV-C the sperm count dropped and the sperm had "deformities of the acro some and destruction of flagellum, resulting in a subsequent decline in the fertilization rate of eggs" (Au et al. 2002). From this study, we can see that increased UV radiation can also cause infertility. Human male fertility is thought to have decreased by 50% as a result of exposure to estrogen mimicking chemicals, these include pesticides such as DDT, industrial chemicals and other natural substances. Dr. H.J. Mullers' later studies found that many cancer causing chemicals such as mustard gas produced the same affect as X radiation. Studies done on the exposure of humans to pesticides and fungicides such as Dihydro phenanthrene, Linuron, Vincozolin, DDT / DDE, chlordecone and Flutamide all came to the same conclusion.

After continual exposure to pesticides whether it be through occupational circumstances or other, it was found that males had a decrease in sperm production and sperm motility it was also shown that the sperm became abnormal. Females were also included in this study and it was found that after continual exposure to the pesticides a high number of pregnancies eventuated in a miscarriage, because the embryo is unable to successfully attach its self to the uterus wall and thus can't receive the nutrients it needs to survive. Two other specific studies were done one on the effects of exposure to DDT and exposure to chlordecone. These studies showed that continual exposure to DDT has been shown to block the action of male hormones thus making them sterile. The study done on chlordecone showed that workers exposed to a high level of the pesticide suffered from a decrease in sperm motility and produced abnormal sperm. Another factor in infertility is heavy metals and solvents, which are said to reduce sperm quantities and cause sperm to mutate making fertilization more difficult.

Lead is one of the most common heavy metals humans are in contact with today and recent studies have shown that lead has an adverse affect on human fertility. One study done by the Institute of Occupational Health at the University of Brescia looked at male fertility in the assessment of exposure to lead, which involved a group of males how had occupational exposure to lead. Their studies concluded that after being exposed to lead the workers had a "decrease in sperm count, volume, motility, morphological alterations, endocrine effects" (Apostoli et al. 1999). Another similar study done by the Department of Internal Medicine at the University Hospital in Sweden looked at the effects of lead on lead smelter workers and found similar results.

Another study done was by the National Cancer Institute at the National Institute of Environmental Health Sciences, USA who looked lead interaction with human protamine (HP 2) as a mechanism of male reproductively toxicity. They found that lead had the ability to decrease the level of protamine and DNA interaction, which may result in a reduced sperm count and therefore reduced fertility. It has also been proven that human interaction, either directly or indirectly to mercury can also cause infertility. A study done by the Ecology and Biodiversity Department at the University of Hong Kong studied the relationship between infertility and fish consumed from the mercury-polluted waters surrounding Hong Kong. This study tested both fertile and infertile males for mercury found in their hair. It was proven that infertile males had approximately 40% more mercury in their hair than fertile males of a similar age.

The mercury also affected females but not to such a significant extent. I must also note that in this particular study a group of vegans who had consumed no fish were also tested they found that the vegans had extremely low levels of mercury in their hair, thus tying the mercury back to the consumption of the fish. It is not only through the food we eat that we can ingest harmful toxins such as mercury but also through the water we drink, as the team from the Department of Applied Biological Sciences at Jordan University of Science and Technology found. This group studied the effects of long term exposure to manganese (Mn) chloride on the fertility of male and female mice through drinking water. This study showed that male mice exposed a manganese (Mn) chloride solution at a concentration of 8000 mg / l had a significant reduction in fertility however there was no significant affect at lower concentrations. In female mice, exposure to manganese (Mn) chloride solution at a concentration of 8000 mg / l reduced the number of implantation's and viable fetuses.

This study also showed that manganese (Mn) sulfate had similar results to the maganese (Mn) chloride. The study also made note of occupations that expose humans to a toxic levels of maganese (Mn) or maganese (Mn) containing compounds " production of paint pigments, dry batteries, glass and ceramics as well as mining maganese ores and welding of mild steel - may expose workers to excessive amounts of this chemical. Toxic exposure to Mn (through the air or diet) has been shown to result in extensive neural damage, reproductive and immune system dysfunction, as well as hepatic and testicular damage" (Donaldson et al. 2000).

A group from the University Centre Nijmegen in The Netherlands studies the impact of calcium (Ca), magnesium (Mg), zinc (Zn) and copper (Cu) in blood and seminal plasma on semen parameters in men. This group tested 107 fertile and 103 infertile men and they found that the infertile men had significantly higher concentrations of calcium (Ca), magnesium (Mg), zinc (Zn) and copper (Cu) in their blood and their seminal plasma. 82% of the infertile men had subnormal quantities of one or more of these elements. "The sperm concentration, motility, and normal morphology were significantly lower in sub fertile males than in fertile males". (Wong et al. 2000) When the elements were tested separately and analyzed, the group found that they could make no conclusions on the affect copper (Cu) or calcium (Ca) had on human fertility.

However, the group found that high zinc (Zn) concentrations caused a lowered sperm count, motility and could cause mutations and magnesium (Mg) had a very similar affect to zinc (Zn) however it did not seem to affect sperm motility. There are many environmental factors that have adverse affects on human fertility, above we have seen examples from the three major groups: heavy metals, industrial pollutants and pesticides / fungicides. In every example we were shown how fertility in humans was declining especially in males, "due to a higher surface area to volume ratio, sperm are usually more sensitive to toxicant exposure than eggs" (Pagano, 1995). Overall, there is enough proof to say that human fertility is declining because of pollution.

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