II. Environmental Risks — Recent Research Findings:
Paternal Occupation and Risk of Birth Defects in Offspring.
By P.G. Schnitzer, A.F. Olshan, and J.D. Erickson (1995). Epidemiology 6 (6), 577-583.
Case-controlled findings from the Metropolitan Atlanta Congenital Defects Program involved over 6,000 fathers. Considering occupation around the time of conception and the birth defects which were registered during the years 1968-1980, researchers figured odds ratios (OR) for 28 specific birth defects by comparing fathers of this occupation with all other occupations combined. Calculations are presented for five occupations where odds ratios from 1.5 to 9.0 were found associated with numerous types of birth defects.
Printers had an odds ratio of 9.0 for gall bladder and liver anomalies, possibly due to their exposure to lead and solvents, while food processors showed elevated odds for the brain abnormalities hydrocephalus and microcephalus, perhaps due to exposure to pesticides or preservatives. Electronic equipment operators, exposed to electromagnetic fields and radiofrequency radiation had elevated odds for arm deformities and spina bifida. Vehicle manufacturers had positive associations with ten defects, more than any other occupation, possibly related to potential exposure to solvents and metals. Odds were elevated for Anencephalus (4.6), Rectum and anus abnormalities (5.1), and cleft lip (4.7).
Relation of Exposure to Airway Irritants in Infancy to Prevalence of Bronchial Hyper-Responsiveness in Schoolchildren.
By V. Soyseth, J. Kongerud, D. Haarr, O. Strand, R. Bolle, and J. Boe (1995). The Lancet, 345 (Jan. 28, 1995), 217-220.
To find out whether exposure to sulphur dioxide during infancy is related to the prevalence of bronchial hyper-responsiveness (BHR) in children, researchers studied schoolchildren ages 7-13 from two valleys of Norway. The valleys, at opposite ends of a 12 km lake, were similar in all respects except that one had a smelter producing 180,000 tons of aluminum and the other a plant producing 100,000 tons of carbon anodes for the smelter each year. The smelter produced emissions of sulphur dioxide and fluoride. Children were exposure-rated, depending on the duration of residence.
Of the 529 children tested, 79 (14.9%) were diagnosed as having BHR. Far more were in the town with the smelter: 65 cases compared to 14. A dose-relationship was found between the cumulative amount of exposure and the prevalence of BHR. Calculations showed that living in the area in the first three years of life was associated with the prevalence of BHR in later childhood. The sick children had a history of wheezing bronchitis during the first two years. The longer they lived there, the worse they got. Typically, there was a time lag of three to six years between exposure and the full blossoming of the disease.
Effects of Prenatal PCB Exposure on Cognitive Processing Efficiency and Sustained Attention.
By J.L. Jacobson, S.W. Jacobson, R.J. Padgett, G. Brummitt, et. al. (1992). Developmental Psychology, 28(2), 297-306.
This is a study of four-year-olds who were exposed prenatally to the environmental toxin polychlorinated biphenyls (PCB). Tests of their cognitive abilities revealed they were less efficient in visual discrimination processing and made more errors in short-term memory, two key areas fundamental to learning. Sustained attention was not affected. Although much larger quantities of these contaminents are transferred postnatally via breastmilk than prenatally across the placenta, postnatal exposure was unrelated to cognitive performance. This indicates the damage is done in the prenatal period when the brain is under construction.
Synergistic Activation of Estrogen Receptors with Combinations of Environmental Chemicals.
By S.F. Arnold, D.M. Klotz, B.M. Collins, P.M Vonier, L.J.Guillette, and J.A. McLachlan (1996) Science, 272 (7 June), 1489-1492.
The most recent threat to reproductive health is the accumulation of abnormally high concentrations of estrogenic compounds in the public environment. Estrogen in its natural place, in the right proportions, and in the correct sequences plays many roles in sexual development. When it is let loose in the environment, however, it can play havoc with male and female sexuality, fertility, sperm morphology, semen production, and may contribute to cancer of sexual organs like the testicles, cervix, and breast.
Modern sources of estrogenic compounds include all of the following: direct prescription of synthetic estrogen, estrogens in contraceptive pills, estrogens in food and dairy products, and estrogen in a growing list of pesticides and pollutants which reach us every day in air food, and water. Among the pollutants which mimic estrogen are alkylphenol polyethoxylates (AKE) which are widely used in detergents and end up in the water supply. Bisphenol-A is also estrogenic and is used to coat food cans, bottle tops, and water pipes.
In this research, a team of scientists at Tulane University discovered that compounds of estrogenic pesticides have a synergistic effect and become as much as a thousand times more potent in activating human estrogenic responses. The specific chemicals studied were endosulphan, dieldrin, chlordane, and toxaphene. This finding ended complacency about the relatively harmless effect of just one of these substances acting alone.