Andrew S. Rowland

Reduced fertility among women employed as dental assistants exposed to high levels of nitrous oxide

BACKGROUND Fertility is reduced in female rats exposed to levels of nitrous oxide similar to those found in some dental offices. Epidemiologic studies have suggested an association between exposure to mixed anesthetic gases and impaired fertility. We investigated the effects of occupational exposure to nitrous oxide on the fertility of female dental assistants. METHODS Screening questionnaires were mailed to 7000 female dental assistants, ages 18 to 39, registered by the California Department of Consumer Affairs. Sixty-nine percent responded. Four hundred fifty-nine women were determined to be eligible, having become pregnant during the previous four years for reasons unrelated to the failure of birth control, and 91 percent of these women completed telephone interviews. Detailed information was collected on exposure to nitrous oxide and fertility (measured by the number of menstrual cycles without contraception that the women required to become pregnant). RESULTS After controlling for covariates, we found that women exposed to high levels of nitrous oxide were significantly less fertile than women who were unexposed or exposed to lower levels of nitrous oxide. The effect was evident only in the 19 women with five or more hours of exposure per week. These women were only 41 percent (95 percent confidence interval, 23 to 74 percent; P less than 0.003) as likely as unexposed women to conceive during each menstrual cycle. CONCLUSIONS Occupational exposure to high levels of nitrous oxide may adversely affect womens ability to become pregnant.

Reliability of reporting on life-style and agricultural factors by a sample of participants in the Agricultural Health Study from Iowa.

Repeat interviews from 4,088 Iowa pesticide applicators participating in the Agricultural Health Study provided the opportunity to evaluate the reliability of self-reported information on pesticide use and various demographic and life-style factors. Self-completed questionnaires were administered 1 year apart when participants returned to county agricultural extension offices for pesticide certification or training. Percentage agreement for ever-/never-use of specific pesticides and application practices was quite high, generally ranging from 70% to more than 90%, and did not vary by age, educational level, or farm size. Agreement was lower (typically 50–60%) for duration, frequency, or decade of first use of specific pesticides. Level of agreement regarding pesticide use in this population is similar to that generally found for factors typically used in epidemiologic studies such as tobacco use and higher than typically reported for diet, physical activity, and medical conditions.

Influence of Medical Conditions and Lifestyle Factors on the Menstrual Cycle

Background. Few studies have described medical and lifestyle factors associated with various menstrual cycle characteristics. Methods. We analyzed cross-sectional data collected from 3941 premenopausal women from Iowa or North Carolina participating in the Agricultural Health Study between 1994 and 1996. Eligible women were age 21–40, not taking oral contraceptives, and not currently pregnant or breast feeding. We examined four menstrual cycle patterns: short cycles (24 days or less), long cycles (36 days or more), irregular cycles, and intermenstrual bleeding. Results. Long and irregular cycles were less common with advancing age and more common with menarche after age 14, with depression, and with increasing body mass index. The adjusted odds of long cycles increased with increasing body mass index, reaching 5.4 (95% confidence interval [CI] = 2.1–13.7) among women with body mass indexes of 35 or higher compared with the reference category (body mass index of 22–23). Smoking was associated with short cycles. Long cycles, irregular cycles, and intermenstrual bleeding were associated with a history of infertility. Having long cycles was associated with a doubling in the adjusted odds of having a fetal loss among women who had been pregnant within the last 5 years (odds ratio = 2.3; 95% CI = 0.9–5.7). Conclusions. Menstrual patterns are influenced by a number of host and environmental characteristics. Factors that perturb menstruation may increase a woman’s risk of other reproductive disorders.

The effect of occupational exposure to mercury vapour on the fertility of female dental assistants.

Exposure to mercury vapour or inorganic mercury compounds can impair fertility in laboratory animals. To study the effects of mercury vapour on fertility in women, eligibility questionnaires were sent to 7000 registered dental assistants in California. The final eligible sample of 418 women, who had become pregnant during the previous four years, were interviewed by telephone. Detailed information was collected on mercury handling practices and the number of menstrual cycles without contraception it had taken them to become pregnant. Dental assistants not working with amalgam served as unexposed controls. Women with high occupational exposure to mercury were less fertile than unexposed controls. The fecundability (probability of conception each menstrual cycle) of women who prepared 30 or more amalgams per week and who had five or more poor mercury hygiene factors was only 63% of that for unexposed women (95% CI 42%-96%) after controlling for covariates. Women with low exposure were more fertile, however, than unexposed controls. Possible explanations for the U shaped dose response and limitations of the exposure measure are discussed. Further investigation is needed that uses biological measures of mercury exposure.

Ethylene oxide exposure may increase the risk of spontaneous abortion, preterm birth, and postterm birth.

&NA; Ethylene oxide is a gas used in some dental offices to sterilize equipment. In pregnant laboratory animals, ethylene oxide increases malformations and fetal loss. Increased gestation length has also been reported. In humans, two studies have reported increased spontaneous abortions among ethylene oxide‐exposed women, but few other data exist. We sent questionnaires to 7,000 dental assistants, age 18‐39 years, registered in California in 1987; 4,856 responded (69%). We based our analysis on 1,320 women whose most recent pregnancy was conceived while working full‐time. Thirty‐two women reported exposure to ethylene oxide; unexposed dental assistants comprised the comparison group. We estimated relative risks of spontaneous abortion and preterm birth using a person‐week model. We estimated relative risks of postterm birth (≥42 weeks) and a combined adverse outcomes model using logistic regression. Among exposed women, the age‐adjusted relative risk of spontaneous abortion was 2.5 [95% confidence interval (CI) = 1.0‐6.3], for preterm birth 2.7 (95% CI = 0.8‐8.8), and for postterm birth 2.1 (95% CI = 0.7‐5.9). The estimated relative risk of any of these adverse outcomes among exposed women was 2.5 (95% CI = 1.0‐6.1) after adjusting for age, nitrous oxide, and number of mercury amalgams prepared. These data further implicate ethylene oxide as a possible reproductive toxicant in humans.

Exposure opportunities of families of farmer pesticide applicators.

BACKGROUNDnFamilies of farmer pesticide applicators have unusual opportunities for exposure, directly or indirectly, to pesticides. These exposures are not well characterized.nnnMETHODSnSubjects were 26,793 licensed private pesticide applicators enrolled in the Agricultural Health Study, a cohort study being conducted in Iowa and North Carolina. Questionnaires were completed by the applicators and their spouses.nnnRESULTSnMany indirect exposure opportunities exist; for example, 21% of homes are within 50 yards of pesticide mixing areas, 27% of applicators store pesticides in their homes, and 94% of clothing worn for pesticide work is washed in the same machine as other laundry. Direct exposure opportunities also occur; for example, 51% of wives of applicators worked in the fields in the last growing season, 40% of wives have ever mixed or applied pesticides, and over half of children aged 11 or more do farm chores.nnnDISCUSSION/CONCLUSIONSnThe extent of the opportunities for exposure of family members of farmer pesticide applicators makes studies of their health important.

Retinal degeneration in licensed pesticide applicators

BACKGROUNDnRetinal degeneration is the leading cause of visual impairment in older adults, but little is known about its relationship to neurotoxic exposures.nnnMETHODSnThe Agricultural Health Study is a cohort study of licensed pesticide applicators from Iowa and North Carolina. We used cross-sectional data from self-administered questionnaires given at enrollment in 1994-1996 to compare pesticide use in 154 applicators who reported retinal degeneration and 17,804 controls.nnnRESULTSnRetinal degeneration was associated with fungicide use (odds ratio = 1.8, 95% confidence interval = 1.3-2.6). This relationship was seen in subgroups defined by state, demographic characteristics, or medical history, as well as in the entire group. Risk increased with cumulative days of fungicide use (P for trend = 0.011) and was greater when application methods involving greater personal exposure were used. Retinal degeneration was also related to use of organochlorine or carbamate insecticides, but these associations were less consistent. Since nearly all applicators used organophosphate insecticides and herbicides, these exposures could not be effectively evaluated.nnnCONCLUSIONSnThese results suggest that exposure to some fungicides and insecticides may increase risk of retinal degeneration.

Reduced Fertility among Women Employed as Dental Assistants Exposed to High Levels of Nitrous Oxide

Abstract Background. Fertility is reduced in female rats exposed to levels of nitrous oxide similar to those found in some dental offices. Epidemiologic studies have suggested an association between exposure to mixed anesthetic gases and impaired fertility. We investigated the effects of occupational exposure to nitrous oxide on the fertility of female dental assistants. Methods. Screening questionnaires were mailed to 7000 female dental assistants, ages 18 to 39, registered by the California Department of Consumer Affairs. Sixty-nine percent responded. Four hundred fifty-nine women were determined to be eligible, having become pregnant during the previous four years for reasons unrelated to the failure of birth control, and 91 percent of these women completed telephone interviews. Detailed information was collected on exposure to nitrous oxide and fertility (measured by the number of menstrual cycles without contraception that the women required to become pregnant). Results. After controlling for covaria...

Fish intake during pregnancy and early cognitive development of offspring

The upside of pregnant women eating fish is that it contains many potentially beneficial nutrients, among them iron and long-chain omega fatty acids. The downside is that it also may contain neurotoxic agents such as methylmercury. The United Kingdom, where fish consumption is high, seemed to offer a good opportunity to identify any associations between fish intake by pregnant women and the early development of language and communication skills. The cohort included 7421 British children born in the years 1991-1992. Mercury was measured in umbilical cord tissue in roughly 15% of the children. Cognitive development was assessed using adaptations of the MacArthur Communicative Development Inventory (MCDI) at age 15 months and the Denver Developmental Screening Test (DTST) at age 18 months. All but 12% of mothers ate fish while pregnant, 80% of them a least once a week. Approximately two thirds ate both white and oily types of fish. Developmental assessment scores consistently increased with greater maternal fish intake during pregnancy. The greatest effect was a 7% higher MCDI comprehension score when mothers ate fish at least once a week, compared with those eating no fish. For MCDI social activity scores, the major difference was between no fish and any fish. Total DDST scores were 2% higher in children whose mothers ate fish 1 to 3 times a week compared with those eating no fish. The chance of making high or low scores, especially on the MCDI, also was associated with maternal fish intake. The childs fish intake did not influence these findings, but it was independently associated with higher neurodevelopmental scores. Fish intake during pregnancy also was associated with increased levels of mercury in umbilical cord tissue. In general, however, mercury levels were low and did not correlate with developmental scores. Moderate intake of noncontaminated fish during pregnancy may enhance the childs early development of language and communication skills.

Reduced Fertility Among Women Employed as Dental Assistants Exposed to High Levels of Nitrous Oxide

BACKGROUNDnFertility is reduced in female rats exposed to levels of nitrous oxide similar to those found in some dental offices. Epidemiologic studies have suggested an association between exposure to mixed anesthetic gases and impaired fertility. We investigated the effects of occupational exposure to nitrous oxide on the fertility of female dental assistants.nnnMETHODSnScreening questionnaires were mailed to 7000 female dental assistants, ages 18 to 39, registered by the California Department of Consumer Affairs. Sixty-nine percent responded. Four hundred fifty-nine women were determined to be eligible, having become pregnant during the previous four years for reasons unrelated to the failure of birth control, and 91 percent of these women completed telephone interviews. Detailed information was collected on exposure to nitrous oxide and fertility (measured by the number of menstrual cycles without contraception that the women required to become pregnant).nnnRESULTSnAfter controlling for covariates, we found that women exposed to high levels of nitrous oxide were significantly less fertile than women who were unexposed or exposed to lower levels of nitrous oxide. The effect was evident only in the 19 women with five or more hours of exposure per week. These women were only 41 percent (95 percent confidence interval, 23 to 74 percent; P less than 0.003) as likely as unexposed women to conceive during each menstrual cycle.nnnCONCLUSIONSnOccupational exposure to high levels of nitrous oxide may adversely affect womens ability to become pregnant.