Fetal loss and work in a waste water treatment plant

Parental concentration of dichlorodiphenyl dichloroethene and polychlorinated biphenyls in Michigan fish eaters and sex ratio in offspring

Contamination of fish in the Great Lakes generated three surveys assessing polychlorinated biphenyls (PCB) serum concentration in Michigan anglers: 1973 to 1974, 1979 to 1982, and 1989 to 1991. This cohort provided 1177 individuals with PCB determinations. In 2000, we conducted telephone interviews with parents on their children's birth characteristics. We estimated the sex odds ratio for parental PCB and dichlorodiphenyl dichloroethene concentrations using generalized estimation equations. We identified 208 offspring, within 101 families, born after 1963, with paternal measurements of both PCB and dichlorodiphenyl dichloroethene. When controlling for maternal exposure and parental dichlorodiphenyl dichloroethene, the sex odds ratio was increased if paternal PCB concentrations exceeded 8.1 micrograms/L (sex ratio, 2.29; 95% confidence interval, 1.11 to 4.74). Thus, paternal exposure was linked to a higher proportion of male offspring. These findings are opposite those reported for the Seveso study and are in accordance with those for dioxin exposure in the American veterans study.

Occupational hazards for the male reproductive system

The etiology of male infertilities is largely undetermined, and our knowledge of exogenous factors affecting the male reproductive system is still limited. In particular, the role of specific environmental and occupational factors is incompletely elucidated. Various occupational (physical and chemical) agents have been shown to affect male reproductive functions in animals, but large differences in reproductive function and/or xenobiotic handling between species limit extrapolation to humans. When available, human data are often conflicting and, except in a few instances, usually refer to broad and heterogenous occupational categories or to groups of agents (e.g., solvents). It is often difficult to elucidate the role of a single agent because occupational exposure conditions are often complex and various confounding factors related to lifestyle (smoking, alcohol, and diet) or socioeconomic state may also affect sperm quality, fertility, or pregnancy outcomes. The objective of this work is to summarize the main epidemiological and, where relevant, experimental findings pertaining to agents (physical and chemical) encountered in the occupational environment that might affect the male reproductive system (sperm count, motility and morphology, libido, and fertility) and/or related pregnancy outcomes (spontaneous abortion, stillbirth, low birth weight, and birth defects and childhood malignancy in offspring). Some methodological issues related to research on the reproductive effects of toxicants are also discussed briefly.

Review of epidemiologic studies of paternal occupational exposure and spontaneous abortion

The question of whether paternal exposures influence risk of spontaneous abortion is of great public interest, with the possibility supported by laboratory investigations. Thirty-nine studies of male occupational exposure and risk of spontaneous abortion were examined, with the methods and results tabulated. Many of those reports were limited by exposure data based on maternal report of the father's job title or by potentially inaccurate paternal reports of spontaneous abortion, though the quality of more recent studies is markedly enhanced. Mercury has been implicated most strongly based on recent studies that included quantitative exposure estimates; a number of studies showing associations for exposure to anesthetic gases. Suggestive associations have also been found inconsistently for exposure to lead, rubber manufacturing, selected solvents, and some pesticides. Further study is encouraged, but with more intensive effort to measure accurately both spontaneous abortion and occupational exposures.

Mental retardation in ten-year-old children in relation to their mothers' employment during pregnancy

We conducted a case-control study to examine relationships between potential risk factors in women's prenatal occupational histories and subsequent mental retardation in their 10-year-old children. Children with mental retardation (intelligence quotient less than 71) were identified from special education records maintained by the public school systems in the metropolitan Atlanta area and from records of various medical and social service agencies serving children with special needs. Control children were chosen from the rosters of 10-year-olds who were enrolled in regular education classes in the local public school systems. To obtain occupational histories, sociodemographic data, and other information, we interviewed 352 natural mothers (67%) of 525 case children and 408 natural mothers (64%) of 636 control children. We computed odds ratios for each of 25 selected occupation, industry, and agent categories controlling for maternal education, birth order, and race. Most comparisons yielded odds ratios that were not indicative of unusual risks, but we did find lower than expected risks among children of teachers and health-care professionals. We also found a strong, positive association between mental retardation and maternal employment in the textile and apparel industries. The findings are useful for planning the direction of future studies of childhood cognitive ability to focus on specific parental occupations or industries.

Effects of paternal occupational exposure on spontaneous abortions

BACKGROUND

Paternal exposure to mutagenic agents has been suggested to affect pregnancy outcome adversely.

METHODS

A nationwide data base of medically diagnosed spontaneous abortions and other pregnancies and national census data was used to evaluate the effects of men's occupational exposures on risk of spontaneous abortion in 99,186 pregnancies in Finland. Census data from the years 1975 and 1980 provided information about the occupation, industry, and socioeconomic status. A job-exposure classification was developed to classify women and their husbands according to possible occupational exposures on the basis of their occupational title and industry.

RESULTS

In 10% of the pregnancies, the husband was exposed to one or more of the mutagens, and the rate of spontaneous abortion was unaffected (OR = 1.0). Of the 25 specific mutagenic exposures evaluated, paternal exposure to four (ethylene oxide, rubber chemicals, solvents used in refineries, and solvents used in the manufacturing of rubber products) was associated with an increased relative risk of spontaneous abortion. In addition, the risk of spontaneous abortion was higher among wives of rubber products workers than among unexposed men.

CONCLUSIONS

Although there is some biological rationale for the findings of this study, these findings need to be confirmed by studies in which individual exposures can be measured directly.

Fertility of workers chronically exposed to chemically contaminated sewer wastes

Few studies have investigated the reproductive effects of exposure to chemical mixtures. The purpose of this study was to assess fertility in males exposed to mixed industrial and domestic wastes. A detailed reproductive history was obtained from the wives of 231 employees in order to evaluate fertility. Daily work records were used to define exposure status. To ascertain problems of infertility, the ratios of observed live births to expected live births (generated from U.S. birth probabilities) for exposed and nonexposed groups were calculated, and the ratios of these Standardized Fertility ratios (SRFs) were compared. Other analyses considered the couples' contraceptive history and preexposure versus postexposure experience. Though multiple statistical approaches were used to examine the data, the conclusion of this study was that exposure to chemical mixtures was not associated with a decrease in the couples' fertility.

Neurotoxic effects of solvent exposure on sewage treatment workers

Nineteen Sewage Treatment Workers (STWs) exposed to industrial sewage that contained benzene, toluene, and other organic solvents at a primary sewage treatment plant in New York City (Plant A) were examined for evidence of solvent toxicity. Fourteen (74%) complained of central nervous system (CNS) symptoms consistent with solvent exposure, including lightheadedness, fatigue, increased sleep requirement, and headache. The majority of these symptoms resolved with transfer from the plant. Men working less than 1 yr at Plant A were more likely to complain of two or more CNS symptoms than men who were working there longer than 1 yr (p = .055). Objective abnormalities in neurobehavioral testing were found in all 4 men working longer than 9 yr at this plant, but in only 5 of 15 employed there for a shorter period (p = .03). These results are consistent with the known effects of solvent exposure. Occupational health personnel must be aware that STWs can be exposed to solvents and other industrial wastes.

Health effects of work at waste water treatment plants: a review of the literature with guidelines for medical surveillance

Potential health hazards associated with work at waste water treatment plants include bacteria, viruses and protozoa in domestic waste and heavy metals and other hazardous substances in industrial wastes. The primary exposure route for hazardous material is through inhalation of aerosols generated in the secondary phase of water treatment that contain pathogenic organisms. Although few epidemiological studies have investigated the health of waste water treatment facility workers, hazards noted have been limited to acute, self-limited gastrointestinal illnesses. Due to the potential for long term or subtle adverse health effects, a medical surveillance program is proposed that includes attention to infectious diseases, such as hepatitis and to illness/absenteeism records.

Sperm as an indicator of reproductive risk among petroleum refinery workers

A questionnaire study of men in a wastewater treatment plant of a petroleum refinery showed twice the rate of fetal loss in the period during employment in the plant compared with the periods before and after. Questions regarding the interpretation of that study and continuing concern about reproductive risk prompted us to perform a cross sectional evaluation of sperm concentration and morphology. After adjustment for an abstinence period, the mean sperm concentration of the 74 unexposed men did not differ significantly from that of the 34 exposed men (79.9 million/cm3 v 68.2 million/cm3, p(1) = 0.16). The two groups also had a similar proportion of sperm with abnormal morphology (49.1% v 44.5%, p(1) = 0.94). This lack of association remained when degree of exposure, age, use of alcohol and marijuana, past illness or fever, use of baths or sauna, and history of urological problems were considered. These results are most consistent with the absence of sperm mediated reproductive problems.

An epidemiologic surveillance program for evaluating occupational reproductive hazards

A noninvasive and inexpensive epidemiologic program for evaluating the possible effects of occupational exposures on fertility is proposed. This surveillance program utilizes reproductive information obtainable from a short questionnaire (1-2 pages in length) or directly from existing medical, employment, or insurance records, and results can be generated readily on a routine basis. This program examines the reproductive experience of the exposed workers in terms of live births compared with that of the US general population with the proper statistical adjustments. It calculates the standardized birth ratios (SBR), adjusting for maternal age, parity, calendar time, and race. Such an analysis will detect whether there is a significant decrease in fertility among a group of employees, and is, therefore, a useful surveillance tool. The proposed method should be viewed as a mechanism to provide an early signal for any potential hazard and to direct priority for other more in-depth epidemiologic or physiologic studies. The procedure is illustrated with data from individuals exposed to EDB, DBCP, and waste-water treatment plant processes. The method can be modified to compare the reproductive performance of an exposed group to that of an internal control group. With an internal control group, additional confounding factors can be taken into consideration. The relative merits of this approach compared to another method of fertility evaluation, semen analysis, are discussed.