Environmental Pollution And Reproductive Health Paper

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Worked on this in 2005, and presented at the National Seminar on Pollution in Urban Industrial Environment.

Worked on this in 2005, and presented at the National Seminar on Pollution in Urban Industrial Environment.

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  • 1. ENVIRONMENTAL POLLUTION AND REPRODUCTIVE HEALTH By, Shradha Diwan 3rd year B.Sc. Dept. of Microbiology St. Xavier’s college. ABSTRACT Reproductive disorders, hormonally related cancers and infertility seem to be on a rise. During the past 50 years the rate of testicular cancer in industrialized countries has increased by a factor of two to four. Breast cancer mortality in the United States has been rising by about one percent per year since 1940s. There is some evidence that sperm counts and semen volume may have declined substantially. There are also signs that abnormal sexual development in infants is increasing. A doubling of the incidence of undescended testes in male infants since 1960 has been reported in the United Kingdom. Today’s increased prevalence of these reproductive problems is puzzling. Although some increases in the cancer rates in the elderly, younger populations have also displayed conditions such as abnormal sexual development in infants and testicular cancer and infertility in young adults. Improved diagnosis may account for some of the increase, but it probably is not the only explanation. To be sure, large quantities of man- made chemicals have been discharged into the environment over the past 50 years, and very few were tested for their reproductive or developmental toxicity. Indeed, it has been discovered that many pesticides and industrial chemicals mimic or interfere with hormones and that some are biologically active in minuscule quantities. WHAT IS AN ENDOCRINE DISRUPTOR? An endocrine disruptor is an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism or its progeny or (sub) populations. A potential endocrine disruptor is an exogenous substance or mixture that possesses properties that might be expected to lead to endocrine disruption in an intact organism, or its progeny, or (sub) populations. Why is there concern about Endocrine disruptors? The last two decades have witnessed growing scientific concerns and public debate over the potential adverse effects that may result from exposure to a group of chemicals that have the potential to alter the normal functioning of the endocrine system in wildlife and humans. Concerns regarding exposures to these EDCs are due primarily to: 1Adverse effects observed in certain wildlife, fish, and ecosystems; 2The increased incidence of certain endocrine-related human diseases; 3Endocrine disruption resulting from exposure to certain environmental chemicals observed in laboratory experimental animals. HOW CAN YOU REDUCE YOUR OWN – AND YOUR FAMILY’S – EXPOSURE TO POTENTIALLY HARMFUL CHEMICALS IN THE ENVIRONMENT?
  • 2. The food you eat is the most important source of exposure to pesticides and other compounds that tend to bioaccumulate. That’s why carefully controlling your diet is the most effective way to limit your exposure. Most importantly, eat fatty animal products sparingly. The chemicals of most concern, PCBs, DDT, and dioxin, tend to accumulate in animal fats. Steer clear of rich cheeses, cream, whole milk, butter, pork, and beef and remove the skin from fish and chicken. By keeping your own percentage of body fat low, you will minimize your body burden of these chemicals. In addition, you should eat plenty of vegetables, grains, beans, and fruit. Women, in particular, may be able to counter some of the effects of estrogenic chemicals with a rich diet in fiber, which appears to reduce the amount of endogenous estrogens that are reabsorbed by the intestine. INTRODUCTION Reproductive disorders, hormonally related cancers and infertility seem to be on a rise. During the past 50 years the rate of testicular cancer in industrialized countries has increased by a factor of two to four. Breast cancer mortality in the United States has been rising by about one percent per year since 1940s. There is some evidence that sperm counts and semen volume may have declined substantially. There are also signs that abnormal sexual development in infants is increasing. A doubling of the incidence of undescended testes in male infants since 1960 has been reported in the United Kingdom. Today’s increased prevalence of these reproductive problems is puzzling. Although some increases in the cancer rates in the elderly, younger populations have also displayed conditions such as abnormal sexual development in infants and testicular cancer and infertility in young adults. Improved diagnosis may account for some of the increase, but it probably is not the only explanation. To be sure, large quantities of man- made chemicals have been discharged into the environment over the past 50 years, and very few were tested for their reproductive or developmental toxicity. Indeed, it has been discovered that many pesticides and industrial chemicals mimic or interfere with hormones and that some are biologically active in minuscule quantities. MATERIALS AND MATTER REPRODUCTIVE BIOLOGY: Human reproduction employs internal fertilization, and depends on the integrated action of hormones, the nervous system, and the reproductive system. Gonads are sex organs that produce gametes. Male gonads are the testes, which produce sperm and male sex hormones. Female gonads are the ovaries, which produce eggs (ova) and female sex hormones. The Male Reproductive System : Testes are suspended outside the abdominal cavity by the scrotum, a pouch of skin that keeps the testes close or far from the body at an optimal temperature for sperm development. Seminiferous tubules are inside each testis, and are where sperm are produced by meiosis. About 250 meters (850 feet) of tubules are packed into each testis. Spermatocytes inside the tubules divide by meiosis to produce spermatids that in turn develop into mature sperm. Male Sex Hormones The anterior pituitary produces follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Action of LH is controlled by the gonadotropin-releasing hormone (GnRH). LH stimulates cells in
  • 3. the seminiferous tubules to secrete testosterone, which has a role in sperm production and developing male secondary sex characteristics. FSH acts on cells to help in sperm maturation. Negative feedback by testosterone controls the actions of GnRH. The Female Reproductive System The female gonads, ovaries, are located within the lower abdominal cavity. The ovary contains many follicles composed of a developing egg surrounded by an outer layer of follicle cells. Each egg begins oogenesis as a primary oocyte. At birth each female carries a lifetime supply of developing oocytes, each of which is in Prophase I. A developing egg (secondary oocyte) is released each month from puberty until menopause, a total of 400-500 eggs. Female Sex Hormones The ovarian cycle is hormonally regulated in two phases. The follicle secretes estrogen before ovulation; the corpus luteum secretes both estrogen and progesterone after ovulation. Hormones from the hypothalamus and anterior pituitary control the ovarian cycle. The ovarian cycle covers events in the ovary; the menstrual cycle occurs in the uterus. Estrogen and progesterone stimulate the development of the endometrium and preparation of the uterine inner lining for implantation of a zygote. If pregnancy does not occur, the drop in FSH and LH cause the corpus luteum to disintegrate. WHAT IS AN ENDOCRINE DISRUPTOR? An endocrine disruptor is an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism or its progeny or (sub) populations. A potential endocrine disruptor is an exogenous substance or mixture that possesses properties that might be expected to lead to endocrine disruption in an intact organism, or its progeny, or (sub) populations. Why is there concern about Endocrine disruptors? The last two decades have witnessed growing scientific concerns and public debate over the potential adverse effects that may result from exposure to a group of chemicals that have the potential to alter the normal functioning of the endocrine system in wildlife and humans. Concerns regarding exposures to these EDCs are due primarily to: 4Adverse effects observed in certain wildlife, fish, and ecosystems; 5The increased incidence of certain endocrine-related human diseases; 6Endocrine disruption resulting from exposure to certain environmental chemicals observed in laboratory experimental animals. These concerns have stimulated many national governments, international organizations, scientific societies, the chemical industry, and public interest groups to establish research programs, organize conferences and workshops, and form expert groups and committees and evaluate EDC-related issues. HOW DO EDCs ACT? Endocrine disrupting chemicals (EDCs) can act in a number of ways in different parts of the body, they may: 1Reduce the production of hormones in endocrine glands; 2Affect the release of hormones from endocrine glands; 3Copy or counteract the action of hormones at target tissues, or 4Speed up the metabolism of hormones and so reduce their action. In many cases, it is not exactly clear how EDCs act, even in some cases where a link has been shown between EDC exposure and an adverse effect.
  • 4. What has been established mainly in the laboratory is: 1Exposure to EDC during early development (e.g. in the womb, during childhood) may cause permanent effects, 2Exposure to EDCs during adult life may not show any significant or visible effects, 3Exposure to EDCs may produce varying effects depending upon the stage of the life cycle or even the season, and 4Unforeseen effects may occur in the target tissues due to endocrine interactions. What are potential sources of EDC exposure? There are two classes of chemicals which can cause endocrine disruption: 1Natural hormones, which include estrogens, progesterone and testosterone found naturally in the bodies of humans and animals, and phytoestrogen substances contained in some plants, such as alfalfa sprouts and soy beans, which display estrogen-like activity when ingested into the body. Natural hormones are believed to be easily broken down in the human body, thus they do not accumulate in body tissues, very unlike the case with certain man- made substances. 2Man-made substances which include: 1. Synthetically produced hormones, including those hormones which are identical to natural hormones, such as oral-contraceptive hormone replacement treatment and some animal feed additives, which have been designed intentionally to interfere with and mostly the endocrine system; and 2. Man-made chemicals designed for uses in industry, such as in indoor cleaning agents, in pesticides, in agriculture, and in consumer goods such as in plastic additives. This group also includes chemicals produced as a by-product of industrial processes such as dioxins. The following groups of chemicals have already been identified as affecting the endocrine system: 1.Polychlorinated biphenyls (PCBs), dioxin and benzopyrene. Interfere with components in the thyroid and retinoid signaling pathways. 2.Products associated with plastics: plasticizers in PVC. 3.Pesticides (insecticides such as DDT, endosulfan, dieldrin, kepone, toxaphene; herbicide as atrazine and nitrofen; fungicides such as benomyl and mancozeb). 4.Ordinary household products such as alkylphenols. 5.Heavy metals like lead, mercury, and cadmium. RESULTS AND DISCUSSION SOME IMPORTANT CASE STUDIES: Health experts of China: Aspermia and deteriorating sperm quality have disqualified 80 percent of volunteer donors to the recently launched Shanghai Human Sperm Bank, according to experts. Prof. Wang Yixin, in charge of the Sperm Bank, warned that worsening male reproductive health has become a noticeable problem in China. Over 85 percent of the 700 volunteer sperm donors are university students. However, most of
  • 5. them have so far produced sperm falling short of the Bank’s requirements. Experts blamed environmental pollution for this, as well as factors such as physical and psychological pressure. Gao Ersheng, a reproduction expert, said that there are now some six million chemicals infesting the earth. Some 60,000 to 70,000 of them are connected with human life, which are increasing at an annual rate of some 3 percent. Statistics show that 20 percent of the chemicals connected with human life carry reproductive toxins. Although Shanghai has embarked some 60 million yuan (about US$7.3billion) to alleviate environmental pollution over that past ten years, the metropolis is still facing many problems in its efforts to protect the environment. People are exposed to endocrine pollutants contained in vehicle exhaust gas, water and other mediums. These pollutants are absorbed into the body by eating, drinking, breathing and physical contact, according to the experts. Male sterility, fetal pathological changes and deteriorating immune functions are some of the typical health problems caused by environmental pollution. According to the Experts, cases of mammary and uterine cancers have increased by 56 and 76 percent, respectively, in Shanghai over the past 20 years. They also link a marked rise in teenage obesity and sexual immaturity to pollution. Other important revelations: The groundwork for adult reproductive function is laid during embryonic and fetal development. Exposure to estrogenic chemicals in the womb could derail normal male development and cause an array of reproductive disorders, presumably by altering the normal multiplication of Sertoli cells in the testes. Indeed, the more subtle consequences of in utero exposures may not become apparent until puberty or adulthood. This was first demonstrated when a high percentage of women exposed in utero to diethylstilbestrol (DES) a potent estrogenic drug to prevent miscarriage – developed clear cell adenocarcinom ( CCAC ) of the vagina and cervix during their late teens and twenties. The appearance of this rare cancer was directly linked to in utero exposure to DES. The sons of women who took DES, in addition to showing increased rates of chryptochidism and hypospadias at birth, are more likely to suffer during adulthood from low sperm counts and decreased semen volume. One study suggests that low dose exposures in the womb to PCBs may affect the neurological development of children. HOW CAN YOU REDUCE YOUR OWN – AND YOUR FAMILY’S – EXPOSURE TO POTENTIALLY HARMFUL CHEMICALS IN THE ENVIRONMENT? The food you eat is the most important source of exposure to pesticides and other compounds that tend to bioaccumulate. That’s why carefully controlling your diet is the most effective way to limit your exposure. Most importantly, eat fatty animal products sparingly. The chemicals of most concern, PCBs, DDT, and dioxin, tend to accumulate in animal fats. Steer clear of rich cheeses, cream, whole milk, butter, pork, and beef and remove the skin from fish and chicken. By keeping your own percentage of body fat low, you will minimize your body burden of these chemicals. In addition, you should eat plenty of vegetables, grains, beans, and fruit. Women, in particular, may be able to counter some of the effects of estrogenic chemicals with a rich diet in
  • 6. fiber, which appears to reduce the amount of endogenous estrogens that are reabsorbed by the intestine. REFERENCES FROM THE INTERNET: http://www.greenfacts.org/endocrine-disruptors/l-3/endocrine-disruptors-1.htm#1 http://www.psratlanta.org/index.html http://ec.europa.eu/research/endocrine/background_system_en.html http://website.lineone.net/~mwarhurst/index.html TEXTS: Fundamentals of Ecology- E.P.Odum.