Showing papers in "Epidemiology in 1999"

Causal diagrams for epidemiologic research.

Abstract: Causal diagrams have a long history of informal use and, more recently, have undergone formal development for applications in expert systems and robotics. We provide an introduction to these developments and their use in epidemiologic research. Causal diagrams can provide a starting point for identifying variables that must be measured and controlled to obtain unconfounded effect estimates. They also provide a method for critical evaluation of traditional epidemiologic criteria for confounding. In particular, they reveal certain heretofore unnoticed shortcomings of those criteria when used in considering multiple potential confounders. We show how to modify the traditional criteria to correct those shortcomings.

Maternal pesticide exposure from multiple sources and selected congenital anomalies.

Abstract: We explored the relation between various potential sources of maternal periconceptional pregnancy exposures to pesticides and congenital anomalies in offspring. Data were derived from a case-control study of fetuses and liveborn infants with orofacial clefts, neural tube defects, conotruncal defects, or limb anomalies, among 1987-1989 California births and fetal deaths. We conducted telephone interviews with mothers of 662 (85% of eligible) orofacial cleft cases, 265 (84%) neural tube defect cases, 207 (87%) conotruncal defect cases, 165 (84%) limb cases, and 734 (78%) nonmalformed controls. The odds ratio (OR) estimates did not indicate increased risk for any of the studied anomaly groups among women whose self-reported occupational tasks were considered by an industrial hygienist likely to involve pesticide exposures. Paternal occupational exposure to pesticides, as reported by the mother, revealed elevated ORs for only two of the cleft phenotypes [OR = 1.7 [95% confidence interval (CI) = 0.9-3.4] for multiple cleft lip with/without cleft palate and OR = 1.6 [95% CI = 0.7-3.4] for multiple cleft palate]. Use of pesticide products for household gardening, by mothers or by professional applicators, was associated with ORs > or =1.5 for most of the studied anomalies. Use of pesticide products for the control of pests in or around homes was not associated with elevated risks for most of the studied anomalies, although women who reported that a professional applied pesticides to their homes had increased risks for neural tube defect-affected pregnancies [OR = 1.6 (95% CI = 1.1-2.5)] and limb anomalies [OR = 1.6 (95% CI = 1.0-2.7)]. Having a pet cat or dog and treating its fleas was not associated with increased anomaly risk. Women who reported living within 0.25 miles of an agricultural crop revealed increased risks for offspring with neural tube defects [OR = 1.5 (95%CI = 1.1-2.1)]. For many of the comparisons, data were sparse, resulting in imprecise effect estimation. Despite our investigating multiple sources of potential pesticide exposures, without more specific information on chemical and level of exposure, we could not adequately discriminate whether the observed effects are valid, whether biased exposure reporting contributed to the observed elevated risks, or whether nonspecific measurement of exposure was responsible for many of the observed estimated risks not being elevated.

Body weight, body mass index, and incident symptomatic osteoarthritis of the hand, hip, and knee.

Abstract: Studies have shown a positive association between obesity and knee osteoarthritis. Studies evaluating hand or hip osteoarthritis and weight, however, have assessed x-ray osteoarthritis or been cross-sectional, or both, and results of these have been inconsistent. We assessed the association between

Reproducibility and validity of maternal recall of pregnancy-related events.

Abstract: We assessed the reproducibility and validity of a questionnaire that asks mothers to recall pregnancy-related events from thirty or more years ago Among 146 women who completed the questionnaire twice, responses were highly reproducible for pre-pregnancy height and weight (r = 095), pregnancy complications (r = 074), substance use (r = 080), preterm delivery (r = 082), birthweight (r = 094), and breastfeeding (r = 089) Among 154 women whose questionnaire responses were compared to data collected during their pregnancies, recall was highly accurate for height (r = 090), pre-pregnancy weight (r = 086), birthweight (r = 091), and smoking (sensitivity = 086, specificity = 094) These findings suggest that long-term maternal recall is both reproducible and accurate for many factors related to pregnancy and delivery

Prenatal methylmercury exposure as a cardiovascular risk factor at seven years of age.

Abstract: Because previous findings have been inconsistent, we explored the association of serum concentrations of uric acid with all-cause and cardiovascular disease mortality and myocardial infarction prospectively. We used data from 1,044 men who are members of the World Health Organization Monitoring Trends and Determinants in Cardiovascular Diseases (MONICA) Augsburg cohort. The men, 45-64 years of age in 1984-1985, were followed through 1992. There were 90 deaths, 44 of which were related to cardiovascular disease; 60 men developed incident nonfatal or fatal myocardial infarction. We estimated hazard rate ratios from Cox proportional hazard models. Uric acid levels > or =373 micromol/liter (fourth quartile) vs < or =319 micromol/liter (first and second quartile) independently predicted all-cause mortality [hazard rate ratio = 2.8; 95% confidence interval (CI) = 1.6-5.0] after adjustment for alcohol, total cholesterol/high-density lipoprotein cholesterol ratio, hypertension, use of diuretic drugs, smoking, body mass index, and education. The adjusted risk of cardiovascular disease mortality was 2.2 (95% CI = 1.0-4.8), and that of myocardial infarction was 1.7 (95% CI = 0.8-3.3). Although residual confounding cannot be excluded, our results are among the few, in men, demonstrating a strong positive association of elevated serum uric acid with all-cause mortality. Future investigations may be able to evaluate whether uric acid contributes independently to the development of cardiovascular disease or is simply a component of the atherogenic metabolic condition known as the insulin resistance syndrome.

Air pollution and infant mortality in Mexico City.

Abstract: Historic air pollution episodes of the 1950s led to acute increases in infant mortality, and some recent epidemiologic studies suggest that infant or child mortality may still result from air pollution at current levels. To investigate the evidence for such an association, we conducted a time-series study of infant mortality in the southwestern part of Mexico City in the years 1993 to 1995 using mortality data from death registrations and air pollution measurements from a monitoring station we operated. Excess infant mortality was associated with the level of fine particles in the days before death, with the strongest association observed for the average concentration of fine particles during the period 3 to 5 days previously: a 10-microg m(-3) increase in the mean level of fine particles during these 3 days was associated with a 6.9% excess of infant deaths (95% confidence interval 2.5-11.3%). Infant mortality was also associated with the levels of nitrogen dioxide and ozone 3 to 5 days before death, but not as consistently as with particles.

How Much Global Ill Health Is Attributable to Environmental Factors

Abstract: Over the years, estimates have been made of the portions of human mortality and morbidity that can be attributed to environmental factors. Frustratingly, however, even for a single category of disease such as cancer, these estimates have often varied widely. Here we attempt to explain why such efforts have come to such different results in the past and to provide guidance for doing such estimates more consistently in the future to avoid the most important pitfalls. We do so by carefully defining what we mean by the terms "environmental," "ill health," and "attributable." Finally, based on these recommendations, we attempt our own estimate, appropriately qualified according to the many remaining uncertainties. Our estimate is that 25-33% of the global burden of disease can be attributed to environmental risk factors. Children under 5 years of age seem to bear the largest environmental burden, and the portion of disease due to environmental risks seems to decrease with economic development. A summary of these estimates first appeared in the 1997 report, "Health and Environment in Sustainable Development," which was the World Health Organization's contribution to the 5-year anniversary of the Rio Earth Summit. A full explanation of how these estimates were made is first presented here. We end with a call for a program of "strategic epidemiology," which would be designed to fill important gaps in the understanding of major environmental health risks in important population groups worldwide.

The health effects of swimming in ocean water contaminated by storm drain runoff.

Abstract: Waters adjacent to the County of Los Angeles (CA) receive untreated runoff from a series of storm drains year round. Many other coastal areas face a similar situation. To our knowledge, there has not been a large-scale epidemiologic study of persons who swim in marine waters subject to such runoff. We report here results of a cohort study conducted to investigate this issue. Measures of exposure included distance from the storm drain, selected bacterial indicators (total and fecal coliforms, enterococci, and Escherichia coli), and a direct measure of enteric viruses. We found higher risks of a broad range of symptoms, including both upper respiratory and gastrointestinal, for subjects swimming (a) closer to storm drains, (b) in water with high levels of single bacterial indicators and a low ratio of total to fecal coliforms, and (c) in water where enteric viruses were detected. The strength and consistency of the associations we observed across various measures of exposure imply that there may be an increased risk of adverse health outcomes associated with swimming in ocean water that is contaminated with untreated urban runoff.

On the comparable quantification of health risks: lessons from the Global Burden of Disease Study.

Abstract: Extensive discussion and comments on the Global Burden of Disease Study findings have suggested the need to examine more carefully the basis for comparing the magnitude of different health risks. Attributable burden can be defined as the difference between burden currently observed and burden that would have been observed under an alternative population distribution of exposure. Population distributions of exposure may be defined over many different levels and intensities of exposure (such as systolic or diastolic blood pressure on a continuous scale), and the comparison distribution of exposure need not be zero. Avoidable burden is defined as the reduction in the future burden of disease if the current levels of exposure to a risk factor were reduced to those specified by the counterfactual distribution of exposure. Choosing the alternative population distribution for a variable, the counterfactual distribution of exposure, is the critical step in developing a more general and standardized concept of comparable, attributable, or avoidable burden. We have identified four types of distributions of exposure that could be used as the counterfactual distributions: theoretical minimum risk, plausible minimum risk, feasible minimum risk, and cost-effective minimum risk. Using tobacco and alcohol as examples, we explore the implications of using these different types of counterfactual distributions to define attributable and avoidable burden. The ten risk factor assessments included in the Global Burden of Disease Study reflect a range of methods and counterfactual distributions. We recommend that future assessments should focus on avoidable and attributable burden based on the plausible minimum risk counterfactual distribution of exposure.

Neural tube defects and drinking water disinfection by-products.

Abstract: We conducted a population-based case control study of neural tube defects and drinking water contaminants, specifically, disinfection by-products. We used public monitoring records concurrent with the first month of gestation to assess exposure. The prevalence odds ratios (PORs) for the highest tertile of total trihalomethanes compared with the lowest was 1.6 (95% confidence interval [CI] = 0.9-2.70). Surface water source was also associated with neural tube defects (POR = 1.5; 95% CI = 0.9-2.5). Sensitivity analyses restricted to isolated neural tube defect cases and mothers with known residence at conception yielded stronger associations [total trihalomethanes, POR = 2.1 (95% CI = 1.1-4.0); surface water, POR = 1.7 (95% CI = 0.9-3.2)]. Other major groups of disinfection by-products (haloacetic acids and haloacetonitriles) showed little relation to these defects.

Job strain and pregnancy-induced hypertension.

Abstract: In a case-control study we assessed whether exposure to high job strain during the first 20 weeks of pregnancy increases the risk of preeclampsia and gestational hypertension. Cases (128 with preeclampsia and 201 with gestational hypertension) and controls (N = 401) were primiparous women who had a paid occupation for at least 1 week during the first 20 weeks of their pregnancy and who delivered between 1984 and 1986 in 10 hospitals of Quebec, Canada. Based on their job title, we assigned women scores of psychological demand and decision latitude derived from the National Population Health Survey and classified these women as exposed to high (high demand, low latitude) versus low (low demand, high latitude) job strain. Women exposed to high job strain were more likely to develop preeclampsia [adjusted odds ratio (aOR) = 2.1; 95% confidence interval (CI) = 1.1-4.1] than women exposed to low job strain. The risk was quite similar for women exposed to a full-time, high strain job (> or =35 hours per week) (aOR = 2.0) than in a part-time, high strain job (aOR = 1.8). High job strain increased the risk of gestational hypertension slightly (aOR = 1.3; 95% CI = 0.8-2.2). These results indicate that women exposed to high job strain are at higher risk of developing preeclampsia and, to a lesser extent, gestational hypertension.

Beta-carotene intake and risk of postmenopausal breast cancer.

Abstract: We assessed the relation between beta-carotene consumption at various times in life and breast cancer risk by conducting a case-control study nested within a population-based cohort of women screened for breast cancer in Sweden. We conducted a telephone interview with 273 incident breast cancer cases and 371 controls about their diet at various ages throughout their lifetime. Controls were frequency matched to cases on age, month and year of mammography, and county of residence. We used unconditional logistic regression to measure the association between beta-carotene intake and breast cancer risk while adjusting for total energy intake, recency of intake, and the matching variables. Women were at lower risk with increasing levels of reported intake of beta-carotene. This pattern of association between breast cancer and beta-carotene intake was similar at various times before screening. These findings indicate that although diets high in beta-carotene may be associated with lower breast cancer risk, there does not seem to be evidence of a critical time period during which such diets are more relevant.

Fine particles and peak flow in children: acidity versus mass.

Abstract: We assessed the impact of summertime haze episodes on twice daily peak flow measurements of children in Philadelphia, Pennsylvania. Height-adjusted peak flows were regressed on weather and air pollution concentrations. Lower morning peak flows were associated with exposure to inhalable particulate matter (-2.94 liters/minute/18 microg/m3, 95% confidence limits (CL) = -0.56, -5.33), and fine sulfate particles (-2.44 liters/minute/8 microg/m3, 95% CL = -0.36, -4.51). Particle-strong acidity and the coarse particle mass were weakly associated with lower peak flow. Acutely lower peak flows in children were associated with fine sulfate particles, but only weakly with the acidity of the fine particles.

Fecundability in relation to body mass and menstrual cycle patterns.

Abstract: Few studies have investigated the association between body mass index and fecundability, that is, the ability to conceive in a menstrual cycle, among fertile women with normal menstrual cycle pattern. We examined the independent and combined effects of duration and regularity of the menstrual cycle, body mass index, and fecundability from records on pregnant women attending antenatal care at Odense University Hospital, Denmark, between 1972 and 1987. We included only the first birth of each woman who had planned pregnancies and no pre-pregnancy disease (N = 10,903). We estimated the fecundability odds ratio (FR) as the odds of conception in a menstrual cycle. After adjusting for confounders, the fecundability for women with a body mass index >25 kg/m2 was lower than for women with a body mass index of 20-25 kg/m2 [FR = 0.77; 95% confidence interval (CI) = 0.70-0.84]. FR was lower for women with long (>35 days) (FR = 0.74; 95% CI = 0.63-0.87) or irregular cycles (FR = 0.78; 95% CI = 0.70-0.87), even when their body mass index was within the normal range (20-25 kg/m2) and/or their cycles were regular.

Risk factor patterns for cryptorchidism and hypospadias.

Abstract: To evaluate the hypothesis of a common etiology for cryptorchidism and hypospadias, we conducted two case-control studies nested in a nationwide cohort in Sweden, using record linkage between the Inpatient and Birth Registries. Cases were 2,782 and 1,220 boys operated for cryptorchidism or hypospadias, respectively. Five matched controls per case were randomly selected. Pregnancy and perinatal data were prospectively recorded in the Birth Registry. Data were modeled through conditional logistic regression. Both cryptorchidism (odds ratio (OR) = 2.22) and hypospadias (OR = 2.75) were positively associated with other congenital malformations and inversely with maternal parity (OR = 0.77 and 0.52, respectively, for parity 4+ compared with primiparae). There is evidence that being born small-for-gestational-age and before the 33rd gestational week have a greater-than-additive effect with respect to both cryptorchidism (OR = 6.19 vs 1.72 expected) and hypospadias (OR = 4.39 vs 2.60 expected) compared with non-small-for-gestational-age boys born at term. Hypospadias was positively associated with severe preeclampsia (OR = 2.11). We conclude that the etiologies of the two conditions are partly shared.

Control for seasonal variation and time trend in case-crossover studies of acute effects of environmental exposures

Abstract: The case-crossover study design is used to study the triggers of acute outcomes in populations. It controls for all measured and unmeasured time-invariant confounders by design. Studies of environmental triggers of morbidity are potentially confounded by temporal trends in the outcome owing to omitted covariates. We conducted a simulation study of the case-crossover design's ability to control for temporal confounding patterns by design rather than through modeling. We compared five case-crossover control sampling strategies including the matched pair, a symmetric bi-directional, a total history approach, and two approaches proposed by Navidi (Biometrics 1998;54:596-605). We simulated true relative risks (RR) of 1.10 and 2.00 and induced confounding by seasonal patterns as well as linear and nonlinear long-term trends to yield estimated RR values as high as 3.18. The symmetric bi-directional approach was compared across four lag times and controlled for temporal confounding best when the lag was shortest. With a 1-week lag, it estimated the RR values as 1.10 and 2.01. The four other approaches failed to control for the temporal trends. Our simulations show that the symmetric bi-directional case-crossover design can substantially control for temporal confounding by design although it is not as efficient (66%) as Poisson regression analysis.

Association of Serum Uric Acid with All-cause and Cardiovascular Disease Mortality and Incident Myocardial Infarction in the Monica Augsburg Cohort

Abstract: Because previous findings have been inconsistent, we explored the association of serum concentrations of uric acid with all-cause and cardiovascular disease mortality and myocardial infarction prospectively. We used data from 1,044 men who are members of the World Health Organization Monitoring Trends and Determinants in Cardiovascular Diseases (MONICA) Augsburg cohort. The men, 45–64 years of age in 1984–1985, were followed through 1992. There were 90 deaths, 44 of which were related to cardiovascular disease; 60 men developed incident nonfatal or fatal myocardial infarction. We estimated hazard rate ratios from Cox proportional hazard models. Uric acid levels ≥373 μmol/liter (fourth quartile) vs ≤319 μmol/liter (first and second quartile) independently predicted all-cause mortality [hazard rate ratio = 2.8; 95% confidence interval (CI) = 1.6–5.0] after adjustment for alcohol, total cholesterol/high-density lipoprotein cholesterol ratio, hypertension, use of diuretic drugs, smoking, body mass index, and education. The adjusted risk of cardiovascular disease mortality was 2.2 (95% CI = 1.0–4.8), and that of myocardial infarction was 1.7 (95% CI = 0.8–3.3). Although residual confounding cannot be excluded, our results are among the few, in men, demonstrating a strong positive association of elevated serum uric acid with all-cause mortality. Future investigations may be able to evaluate whether uric acid contributes independently to the development of cardiovascular disease or is simply a component of the atherogenic metabolic condition known as the insulin resistance syndrome.

Harvesting-resistant estimates of air pollution effects on mortality.

Abstract: A number of studies have recently shown an association between particle concentrations in outdoor air and daily mortality counts in urban locations. In the public health interpretation of this evidence, a key issue is whether the increased mortality associated with higher pollution levels is restricted to very frail persons for whom life expectancy is short in the absence of pollution. This possibility has been termed the "harvesting hypothesis." We present an approach to estimating the association between pollution and mortality from times series data that is resistant to short-term harvesting. The method is based in the concept that harvesting alone creates associations only at shorter time scales. We use frequency domain log-linear regression to decompose the information about the pollution-mortality association into distinct time scales, and we then create harvesting-resistant estimates by excluding the short-term information that is affected by harvesting. We illustrate the methods with total suspended particles and mortality counts from Philadelphia for 1974-1988. The total suspended particles-mortality association in Philadelphia is inconsistent with the harvesting-only hypothesis, and the harvesting-resistant estimates of the total suspended particles relative risk are actually larger-not smaller-than the ordinary estimates.

Risk of childhood leukemia associated with exposure to pesticides and with gene polymorphisms.

Abstract: We conducted a population-based case-control study of childhood acute lymphoblastic leukemia (ALL) to evaluate the risk posed by reported exposure to pesticides used in and around the home. We compared 491 cases 0-9 years of age to as many controls. We also conducted a case-only study on a subsample of 123 cases to evaluate gene-environment interaction between child genotype and maternal exposure during pregnancy as well as child exposure after birth. We used the polymerase chain reaction (PCR) approach to analyze polymorphisms in CYP1A1, CYP2D6, GSTT1, and GSTM1 genes, which encode enzymes involved in carcinogen metabolism. Indoor use of some insecticides by the owners and pesticide use in the garden and on interior plants, in particular frequent prenatal use, was associated with increased risks up to severalfold in magnitude. Interaction odds ratios were increased among carriers of the CYP1A1m1 and CYP1a1m2 mutations when mother during pregnancy or the child had been exposed to certain indoor insecticides. No such effects were observed in the presence of other tested polymorphisms.

Global estimates of fatal occupational accidents.

Abstract: mated fatal occupational accident rate in the whole world was 14.0 per 100,000 workers, and the total estimated number of fatal occupational accidents was 335,000. The rates are different for individual countries and regions and for separate branches of economic activity. In conclusion, fatal occupational accident figures are higher than previously estimated. The new estimates can be gradually improved by obtaining and adding data from countries where information is not yet available. Sectoral estimates for at least key economic branches in individual countries would further increase the accuracy. (Epidemiology 1999;10:640-646)

Trihalomethanes in public water supplies and adverse birth outcomes.

Abstract: Alcohol has strong antimicrobial activity and stimulates gastric acid secretion. Alcohol consumption may therefore compromise the living conditions of Helicobacter pylori in the stomach. We assessed the relation of alcohol consumption with H. pylori infection among 1,785 participants ages 18-88 in the German National Health and Nutrition Survey. Detailed information on dietary and lifestyle habits was obtained in personal interviews using a standardized food frequency questionnaire. Serum samples were analyzed for H. pylori immunoglobulin G antibodies by enzyme-linked immunosorbent assay. Overall prevalence of H. pylori infection was 39.2%. There was a clear inverse dose-response-relation between reported alcohol consumption and H. pylori infection. The relation persisted after control for potential confounding factors. The adjusted prevalence ratios (95% confidence intervals) for H. pylori infection among persons who consumed up to 10, 10 to 20, and more than 20 gm of alcohol per day compared with non-drinkers were 0.93 (0.77-1.13), 0.82 (0.65-1.04), and 0.71 (0.55-0.92). The inverse relation between alcohol consumption and H. pylori infection was even stronger when individuals with an indication of a recent change of alcohol consumption were excluded from the analysis. These findings support the hypothesis that moderate alcohol consumption may facilitate spontaneous elimination of H. pylori infection among adults.

Global burden of disease and injury due to occupational factors.

Abstract: We made estimates of absolute morbidity and mortality due to occupational factors for the world using all available published data as of 1994, and, where no data were available, applying the most appropriate (in terms of similar economy, race, and environment) age-/sex-/diagnosis-specific incidence and mortality rates to known working population distributions. We report results according to economic groupings determined by the World Bank (World Development Report, 1993) and disease and injury groupings according to The Global Burden of Disease project (1997). This was part of a larger study that estimated the total global disease burden. We present aggregate results and analyses by region and disease. We estimate that approximately 100,000,000 occupational injuries (100,000 deaths) and 11,000,000 occupational diseases (700,000 deaths) occur in the world each year. We regard these as very conservative estimates which, although unavoidably crude, can nevertheless provide a basis for health priority planning at global level.

Ventilation in homes and bronchial obstruction in young children.

Abstract: We assessed the role of ventilation rate in homes in the development of bronchial obstruction during the first 2 years of life. We conducted a matched case-control study based on a cohort of 3,754 newborns in Oslo in 1992-93 that was followed for 2 years. The case series comprised 172 children with bronchial obstruction, and the control series was one-to-one matched for date of birth. Ventilation rate and other building characteristics were measured/collected in home visits, and questionnaires were used to obtain additional information. We found that the risk of bronchial obstruction was not directly associated with the ventilation rate in liters per second and per person (ventilation rate quartiles: 6.9, 11.5 and 17.6 l/s,p [liter/second and person]) in the homes (odds ratio; OR 0.98, 95% confidence interval (CI) 0.96-1.01). The odds ratios of bronchial obstruction were higher in the low air change group (air change rate < or =0.5 h(-1)) than in the high air change group owing to exposure to environmental tobacco smoke (low 1.8; 95% CI: 0.35-9.66; high 1.5; 95% CI: 0.74-3.20), dampness problems (low 9.6; 95% CI: 1.05-87.4; high 2.3; 95% CI: 0.83-6.39), and the presence of textile wall paper (low 3.7; 95% CI: 0.62-21.5; high 1.7; 95% CI 0.72-3.94) and plasticizer-containing surfaces (low 12.6; 95% CI: 1.00-159; high 2.6; 95% CI: 1.02-6.58). Our results are consistent with the hypothesis that low ventilation rates strengthen the effects of indoor air pollutants.

Lung cancer and indoor air pollution arising from chinese-style cooking among nonsmoking women living in Shanghai, China

Abstract: Associations between indoor air pollution from Chinese-style cooking and lung cancer have been found in several investigations. To provide more detailed estimates of the associations while accounting for key confounding factors, we conducted a population-based, case-control study of lung cancer among nonsmoking women living in Shanghai, the People's Republic of China. Five hundred four incident, primary lung cancer cases diagnosed from February 1992 through January 1994 were identified through the population-based Shanghai Cancer Registry. A control group of 601 nonsmoking women was selected randomly from the Shanghai-Residential Registry, and they were frequency-matched to the expected age distribution of the cases. Exposure to indoor air pollutants from Chinese-style cooking was ascertained through in-person interviews. We estimated adjusted odds ratios (OR) and 95% confidence intervals (CI) by unconditional logistic regression. There were similar patterns of excess risk for exposure to indoor air pollutants from Chinese-style cooking across different histological types of lung cancer. Women who did not have a separate kitchen experienced a 28% increased risk of lung cancer (OR = 1.28; 95% CI = 0.98-1.68). We found little association with area of the windows of the apartment where subjects had lived for the longest period of time. Heating cooking oils to high temperatures was associated with a 1.64-fold increased risk of lung cancer (95% CI = 1.24-2.17). An 84% excess risk was found among women who most often cooked with rapeseed oil (OR = 1.84; 95% CI = 1.12-3.02). Lung cancer risks were also related to "considerable" smokiness of the kitchen during cooking (OR = 2.38; 95% CI = 1.58-3.57), frequent eye irritation during cooking (OR = 1.68; 95% CI = 1.02-2.78), to a more than weekly use of frying (OR = 2.09; 95% CI = 1.14-3.84) and deep-frying (OR = 1.88; 95% CI = 1.06-3.32). This population-based case-control study confirmed that exposure to indoor air pollution from Chinese-style cooking, especially cooking unrefined rapeseed oil at high temperatures in woks, may increase the risk of lung cancer.

Health, environment and sustainable development: identifying links and indicators to promote action.

Abstract: This paper discusses the links among health, environment, and sustainable development and presents a framework that extends from the epidemiological domain to the policy domain and includes the driving forces that generate environmental pressures, creating changes in the state of the environment and eventually contributing to human exposures. Health effects are the end result of this complex net of events. Environmental health interventions should not be limited to treatment of cases and directly reducing human exposures. The paper discusses the need for integrated action at all levels and, in particular, on the need to focus on long-term action directed at reducing the driving forces that generate the environmental health threats. Only this approach can achieve sustained health benefits and environmental protection in accord with the principles of sustainable development.

Maternal risk of breast cancer and birth characteristics of offspring by time since birth.

Abstract: We examined the association between birth characteristics of offspring and the subsequent maternal risk of breast cancer in a population-based cohort of 998,499 women, 13 to 48 years of age at entry. There were 9,495 incident cases of breast cancer during 12.8 million person-years of follow-up among these women. Compared with mothers of singleton infants, mothers having a multiple birth had an increased risk of breast cancer in the first 5 years after a birth (relative risk (RR) = 1.8; 95% confidence interval (CI) = 1.1-2.8). The risk for mothers having a heavy-weighted child (>3.75 kg), as compared with a child of light weight (< or =3 kg), was also slightly increased (RR = 1.2; 95% CI = 0.9-1.5). This latter effect was primarily due to an increased incidence of tumors larger than 2 cm at diagnosis (RR = 1.4; 95% CI = 0.9-1.9). Our findings are compatible with the hypothesis that the hormonal level during pregnancy influences the risk of breast cancer in the early years after delivery.

Effect of smoking cessation and tobacco type on the risk of cancers of the upper aero-digestive tract in Brazil.

Abstract: We examined the relation between shift work and occupational nitrous oxide exposure in the second trimester of pregnancy and birth weight and gestational age at delivery among the members of the Swedish Midwives Association. Eighty-four per cent of members who were registered in 1989 responded to a postal questionnaire concerning occupational exposures, including work schedule and the use of nitrous oxide, in relation to each of their pregnancies. We obtained information on births from the Swedish Medical Birth Register. We used models with allowance for dependence between births for the same woman and found that night work was associated with preterm birth (<37 weeks) [odds ratio (OR) = 5.6; 95% confidence limits (CL) = 1.9, 16.4] and to a lesser extent with low birth weight [OR = 1.9 (95% CL = 0.6, 5.8)]. Three-shift work schedule (day, evening, and night rotation) showed a possible association with preterm birth [OR = 2.3 (95% CL = 0.7, 7.3)]. Exposure to nitrous oxide use was associated with reduced birth weight (-77 gm; 95% CL = -129, -24) and an increase in the odds of infants being small for gestational age (< or = 10th percentile of weight for gestational week) (OR = 1.8; 95% CL = 1.1, 2.8).

Magnesium and calcium in drinking water and death from acute myocardial infarction in women

Abstract: A relation between water hardness and cardiovascular death has been shown in previous studies. In this case-control study, we investigated the levels of magnesium and calcium in drinking water and death from acute myocardial infarction among women. The study population encompassed 16 municipalities in southern Sweden. Cases were women who had died from acute myocardial infarction between the ages of 50 and 69 years during 1982-1993 (N = 378), and controls were women who had died from cancer (N = 1,368). We obtained magnesium and calcium concentrations of the individual water sources. We divided the subjects into quartiles and found that odds ratios (ORs) were lower at higher levels of both magnesium and calcium. For the quartile with the highest magnesium levels (> or =9.9 mg/liter), the OR adjusted for age and calcium was 0.70 (95% confidence interval = 0.50-0.99). For calcium, the adjusted OR for the quartile with the highest level (> or =70 mg/liter) was 0.66 (95% confidence interval = 0.47-0.94). The results suggest that magnesium and calcium in drinking water are important protective factors for death from acute myocardial infarction among women.

Synergy between asbestos and smoking on lung cancer risks.

Abstract: We have examined data from 12 epidemiologic studies for quantitative evidence of biologic synergy between asbestos and smoking on lung cancer risks. Estimates of the effect associated with joint exposure to the two agents exceeded the sum of their separate effects in each study. We explored the variations in the strength of the synergistic effect across the studies using three indices: the ratio of the combined effects to the sum of the separate effects of smoking and asbestos (S), the relative excess risk due to interaction (RERI), and the attributable proportion of risk due to interaction (AP). The weighted average of S across all studies was 1.64 (95% confidence interval = 1.33-2.03). The attributable proportion associated with this average S was estimated as 33%, that suggests that one-third of cancer cases among smokers who were exposed to asbestos can be attributed to the synergistic behavior of the two carcinogens, as distinct from their separate effects and those attributable to other ("background") factors.

Particulate and Ozone Pollutant Effects on the Respiratory Function of Children in Southwest Mexico City

Abstract: We assessed the contributions of particulate matter with aerodynamic diameters < or =10 and < or =2.5 microm (PM2.5 and PM10) and ozone (O3) to peak expiratory flow (PEF) and respiratory symptoms in 40 schoolchildren 8-11 years of age for 59 days during three periods in 1991 at a school in southwest Mexico City. We measured peak expiratory flow in the morning on the children's arrival at school and in the afternoon before their departure from school. Separately for morning and afternoon, we normalized each child's daily measurement of peak flow by subtracting his or her mean peak flow from the daily measurement. Child-specific deviations were averaged to obtain a morning and afternoon mean deviation (APEF) for each day. Mean 24-hour O3 level was 52 parts per billion (ppb; maximum 103 ppb); mean 24-hour PM2.5 and PM10 were 30 microg/m3 (maximum 69 microg/m3) and 49 microg/m3 (maximum 87 microg/m3), respectively. We adjusted moving average and polynomial distributed lag multiple regression analyses of APEF vs pollution for minimum daily temperature, trend, and season. We examined effects of PM2.5, PM10, and O3, on deltaPEF separately and in joint models. The models indicated a role for both particles and O3 in the reduction of peak expiratory flow, with shorter lags between exposure and reduction in peak expiratory flow for O3 than for particle exposure (0-4 vs 4-7 days). The joint effect of 7 days of exposure to the interquartile range of PM2.5 (17 microg/m3) and O3 (25 ppb) predicted a 7.1% (95% confidence interval = 11.0-3.9) reduction in morning peak expiratory flow. Pollutant exposure also predicted higher rates of phlegm; colinearity between pollutants limited the potential to distinguish the relative contribution of individual pollutants. In an area with chronically high ambient O3 levels, school children responded with reduced lung function to both O3 and particulate exposures within the previous 1 to 2 weeks.