CC16 polymorphisms in asthma, asthma subtypes, and asthma control in adults from the Agricultural Lung Health Study

BACKGROUND

The club cell secretory protein (CC16) has anti-inflammatory and antioxidant effects and is a potential early biomarker of lung damage. The CC16 single nucleotide polymorphism (SNP) rs3741240 risk allele (A) has been inconsistently linked to asthma; other tagging SNPs in the gene have not been explored. The aim was to determine whether CC16 tagging polymorphisms are associated with adult asthma, asthma subtypes or asthma control in the Agricultural Lung Health Study (ALHS).

METHODS

The ALHS is an asthma case-control study nested in the Agricultural Health Study cohort. Asthma cases were individuals with current doctor diagnosed asthma, likely undiagnosed asthma, or asthma-COPD overlap defined by questionnaire. We also examined asthma subtypes and asthma control. Five CC16 tagging SNPs were imputed to 1000 Genomes Integrated phase 1 reference panel. Logistic regression was used to estimate associations between CC16 SNPs and asthma outcomes adjusted for covariates.

RESULTS

The sample included 1120 asthma cases and 1926 controls of European ancestry, with a mean age of 63 years. The frequency of the risk genotype (AA) for rs3741240 was 12.5% (n = 382). CC16 rs3741240 was not associated with adult asthma outcomes. A tagging SNP in the CC16 gene, rs12270961 was associated with uncontrolled asthma (n = 208, OR_adj= 1.4, 95% CI 1.0, 1.9; p = 0.03).

CONCLUSION

This study, the largest study to investigate associations between CC16 tagging SNPs and asthma phenotypes in adults, did not confirm an association of rs3741240 with adult asthma. A tagging SNP in CC16 suggests a potential relationship with asthma control.

DNA methylation signature of smoking in lung cancer is enriched for exposure signatures in newborn and adult blood

Smoking impacts DNA methylation genome-wide in blood of newborns from maternal smoking during pregnancy and adults from personal smoking. We compared smoking-related DNA methylation in lung adenocarcinoma (61 never smokers, 91 current smokers, and 238 former smokers) quantified with the Illumina450k BeadArray in The Cancer Genome Atlas with published large consortium meta-analyses of newborn and adult blood. We assessed whether CpG sites related to smoking in blood from newborns and adults were enriched in the lung adenocarcinoma methylation signal. Testing CpGs differentially methylated by smoke exposure, we identified 296 in lung adenocarcinoma meeting a P < 10-4 cutoff, while previous meta-analyses identified 3,042 in newborn blood, and 8,898 in adult blood meeting the same P < 10-4 cutoff. Lung signals were highly enriched for those seen in newborn (24 overlapping CpGs, Penrichment = 1.2 × 10-18) and adult blood (66 overlapping CpGs, Penrichment = 1.2 × 10-48). The 105 genes annotated to CpGs differentially methylated in lung tumors, but not blood, were enriched for RNA processing ontologies. Some epigenetic alterations associated with cigarette smoke exposure are tissue specific, but others are common across tissues. These findings support the value of blood-based methylation biomarkers for assessing exposure effects in target tissues.

Maternal levels of perfluoroalkyl substances (PFASs) during pregnancy and childhood allergy and asthma related outcomes and infections in the Norwegian Mother and Child (MoBa) cohort

INTRODUCTION

Prenatal exposure to perfluoroalkyl substances (PFASs) has been inconsistently associated with asthma and allergic diseases and increased number of infections in early childhood. We examined the association of PFASs measured in pregnancy with childhood asthma, allergies and common infectious diseases in a prospective pregnancy cohort followed to age 7 years.

MATERIAL AND METHODS

Six PFASs (out of 19 measured) with at least 80% of measurements above the limit of quantification (LOQ) in maternal plasma during pregnancy in two subcohorts of the Norwegian Mother and Child Cohort Study (MoBa) were analyzed in relation to health outcomes: perfluorooctane sulfonic acid (PFOS), acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), perfluoroundecanoic acid (PFUnDA), and perfluoroheptane sulfonic acid (PFHpS). Follow-up questionnaires were completed at 3 years by 1270 women and at 7 years by 972 women among the 1943 with pregnancy questionnaire and PFAS measures. Health outcomes included parent reports of child's symptoms or doctor diagnosed asthma and allergic conditions at age 7 years and parent-reported frequency of various infections at 3 and 7 years of age. Logistic and Poisson regression were used. The false discovery rate was controlled at 5%. Sensitivity analyses on gender were performed.

RESULTS

Among the allergy and asthma outcomes, a statistically significant inverse association was seen between PFUnDA concentrations and ever having atopic eczema in girls. PFUnDA also tended to be inversely associated with both wheeze and asthma. For infections from 0 to 3 and 6 to 7 years, 11 significant positive associations were seen between PFASs and airways infections (bronchitis/pneumonia, throat infection, pseudocroup), ear infection and gastric flu/diarrhea; whereas 6 inverse associations were seen for pseudocroup, ear infections and urinary tract infections. The majority of the findings with respect to infectious diseases were found in girls only.

DISCUSSION

With the exception of an inverse association between PFUnDA and eczema, and a tendency of a similar association for wheeze and asthma, maternal PFAS levels during pregnancy showed little association with asthma or allergy related outcomes. Findings from the present study suggest immunosuppressive effects of PFASs on airways infections, such as bronchitis/pneumonia and throat infections, as well as diarrhea/gastric flu. Our results indicate a possible role of gender in the PFAS-health outcome associations.

Prediction of gestational age based on genome-wide differentially methylated regions

Background

We explored the association between gestational age and cord blood DNA methylation at birth and whether DNA methylation could be effective in predicting gestational age due to limitations with the presently used methods. We used data from the Norwegian Mother and Child Birth Cohort study (MoBa) with Illumina HumanMethylation450 data measured for 1753 newborns in two batches: MoBa 1, n = 1068; and MoBa 2, n = 685. Gestational age was computed using both ultrasound and the last menstrual period. We evaluated associations between DNA methylation and gestational age and developed a statistical model for predicting gestational age using MoBa 1 for training and MoBa 2 for predictions. The prediction model was additionally used to compare ultrasound and last menstrual period-based gestational age predictions. Furthermore, both CpGs and associated genes detected in the training models were compared to those detected in a published prediction model for chronological age.

Results

There were 5474 CpGs associated with ultrasound gestational age after adjustment for a set of covariates, including estimated cell type proportions, and Bonferroni-correction for multiple testing. Our model predicted ultrasound gestational age more accurately than it predicted last menstrual period gestational age.

Conclusions

DNA methylation at birth appears to be a good predictor of gestational age. Ultrasound gestational age is more strongly associated with methylation than last menstrual period gestational age. The CpGs linked with our gestational age prediction model, and their associated genes, differed substantially from the corresponding CpGs and genes associated with a chronological age prediction model.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-016-1063-4) contains supplementary material, which is available to authorized users.

25-Hydroxyvitamin D in pregnancy and genome wide cord blood DNA methylation in two pregnancy cohorts (MoBa and ALSPAC)

The aim of the study was to investigate whether maternal mid-pregnancy 25-hydroxyvitamin D concentrations are associated with cord blood DNA methylation. DNA methylation was assessed using the Illumina HumanMethylation450 BeadChip, and maternal plasma 25-hydroxyvitamin D was measured in 819 mothers/newborn pairs participating in the Norwegian Mother and Child Cohort (MoBa) and 597 mothers/newborn pairs participating in the Avon Longitudinal Study of Parents and Children (ALSPAC). Across 473,731CpG DNA methylation sites in cord blood DNA, none were strongly associated with maternal 25-hydroxyvitamin D after adjusting for multiple tests (false discovery rate (FDR)>0.5; 473,731 tests). A meta-analysis of the results from both cohorts, using the Fisher method for combining p-values, also did not strengthen findings (FDR>0.2). Further exploration of a set of CpG sites in the proximity of four a priori defined candidate genes (CYP24A1, CYP27B1, CYP27A1 and CYP2R1) did not result in any associations with FDR<0.05 (56 tests). In this large genome wide assessment of the potential influence of maternal vitamin D status on DNA methylation, we did not find any convincing associations in 1416 newborns. If true associations do exist, their identification might require much larger consortium studies, expanded genomic coverage, investigation of alternative cell types or measurements of 25-hydroxyvitamin D at different gestational time points.

Food allergens in mattress dust in Norwegian homes - a potentially important source of allergen exposure

BACKGROUND

Sensitization to food allergens and food allergic reactions are mostly caused by ingesting the allergen, but can also occur from exposure via the respiratory tract or the skin. Little is known about exposure to food allergens in the home environment.

OBJECTIVE

The objective of this study was firstly to describe the frequency of detection of allergens from fish, egg, milk, and peanut in mattress dust collected from homes of 13-year-old adolescents and secondly to identify home characteristics associated with the presence of food allergen contamination in dust.

METHODS

Food allergens were measured by dot blot analysis in mattress dust from 143 homes in Oslo, Norway. We analysed associations between home characteristics (collected by parental questionnaires and study technicians) and food allergens by multivariate regression models.

RESULTS

Fish allergen was detected in 46%, peanut in 41%, milk in 39%, and egg allergen in 22% of the mattress dust samples; only three samples contained none of these allergens. All four food allergens were more frequently detected in mattresses in small dwellings (< 100 m(2)) than larger dwellings (≥ 130 m(2)); 63-71% of the small dwellings (n = 24) had milk, peanut, and fish allergens in the samples compared with 33-44% of the larger dwellings (n = 95). Milk, peanut, and egg allergens were more frequently detected in homes with bedroom and kitchen on the same floor as compared with different floors, with odds ratios of 2.5 (95% confidence interval (CI): 1.1, 5.6) for milk, 2.4 (95% CI: 1.0, 6.1) for peanut, and 3.1 (95% CI: 1.3, 7.5) for egg allergens.

CONCLUSIONS AND CLINICAL RELEVANCE

Food allergens occurred frequently in beds in Norwegian homes, with dwelling size and proximity of kitchen and bedroom as the most important determinants. Due to the amount of time children spent in the bedroom, mattress dust may be an important source of exposure to food allergens.

Adhesion molecules, endothelin-1 and lung function in seven population-based cohorts

CONTEXT

Endothelial function is abnormal in chronic obstructive pulmonary disease (COPD); whether endothelial dysfunction causes COPD is unknown.

OBJECTIVE

Test associations of endothelial biomarkers with FEV1 using instrumental variables.

METHODS

Among 26 907 participants with spirometry, ICAM-1, P-selectin, E-selectin and endothelin-1 were measured in subsets.

RESULTS

ICAM-1 and P-selectin were inversely associated with FEV1 among European-Americans (-29 mL and -34 mL per standard deviation of log-transformed biomarker, p < 0.001), as was endothelin-1 among African-Americans (-22 mL, p = 0.008). Genetically-estimated ICAM-1 and P-selectin were not significantly associated with FEV1. The instrumental variable for endothelin-1 was non-informative.

CONCLUSION

Although ICAM-1, P-selectin and endothelin-1 were inversely associated with FEV1, associations for ICAM-1 and P-selectin do not appear causal.

Triclosan exposure and allergic sensitization in Norwegian children

BACKGROUND

Exposure to the synthetic antimicrobial chemical, triclosan, used in personal care products, has been hypothesized to lead to allergic disease. We investigated whether triclosan exposure was associated with allergic sensitization and symptoms in 10-year-old Norwegian children.

METHODS

Urinary concentrations of triclosan were measured in one first morning void from 623 children, collected during 2001-2004. Logistic regression models, controlling for urine specific gravity, parental allergic disease, maternal education, and household income, were fitted for allergic sensitization (either skin prick test positivity or serum-specific IgE ≥ 0.35 kU/l to at least one of 15 evaluated inhalant and food allergens), current rhinitis, and current asthma (questionnaire and exercise challenge test).

RESULTS

The adjusted odds ratio (aOR) for allergic sensitization among those in the fourth quartile of triclosan concentration was 2.0 [95% confidence interval (CI): 1.1, 3.4] compared with the reference group (<the limit of detection), and the aOR per log(10) unit increase in triclosan was 1.2 (95% CI: 1.0, 1.4). The aOR for current rhinitis was 1.9 (95% CI: 1.1, 3.4) for the fourth quartile and 1.2 (95% CI: 0.97, 1.4) per log(10) unit increase in triclosan.

CONCLUSION

Triclosan concentrations were associated with allergic sensitization, especially inhalant and seasonal allergens, rather than food allergens. Current rhinitis was associated with the highest levels of triclosan, whereas no association was seen for current asthma. These results are consistent with recent findings in other studies and provide additional evidence for an association between triclosan and allergy.

Part 5. Public health and air pollution in Asia (PAPA): a combined analysis of four studies of air pollution and mortality

BACKGROUND

In recent years, Asia has experienced rapid economic growth and a deteriorating environment caused by the increasing use of fossil fuels. Although the deleterious effects of air pollution from fossil-fuel combustion have been demonstrated in many Western nations, few comparable studies have been conducted in Asia. Time-series studies of daily mortality in Asian cities can contribute important new information to the existing body of knowledge about air pollution and health. Not only can these studies verify important health effects of air pollution in local regions in Asia, they can also help determine the relevance of existing air pollution studies to mortality and morbidity for policymaking and environmental controls. In addition, the studies can help identify factors that might modify associations between air pollution and health effects in various populations and environmental conditions. Collaborative multicity studies in Asia-especially when designed, conducted, and analyzed using a common protocol-will provide more robust air pollution effect estimates for the region as well as relevant, supportable estimates of local adverse health effects needed by environmental and public-health policymakers.

SPECIFIC OBJECTIVES

The Public Health and Air Pollution in Asia (PAPA*) project, sponsored by the Health Effects Institute, consisted of four studies designed to assess the effects of air pollution on mortality in four large Asian cities, namely Bangkok, in Thailand, and Hong Kong, Shanghai, and Wuhan, in China. In the PAPA project, a Common Protocol was developed based on methods developed and tested in NMMAPS, APHEA, and time-series studies in the literature to help ensure that the four studies could be compared with each other and with previous studies by following an established protocol. The Common Protocol (found at the end of this volume) is a set of prescriptive instructions developed for the studies and used by the investigators in each city. It is flexible enough to allow for adjustments in methods to optimize the fit of health-effects models to each city's data set. It provides the basis for generating reproducible results in each city and for meta-estimates from combined data. By establishing a common methodology, factors that might influence the differences in results from previous studies can more easily be explored. Administrative support was provided to ensure that the highest quality data were used in the analysis. It is anticipated that the PAPA results will contribute to the international scientific discussion of how to conduct and interpret time-series studies of air pollution and will stimulate the development of high-quality routine systems for recording daily deaths and hospital admissions for time-series analysis.

METHODS

Mortality data were retrieved from routine databases with underlying causes of death coded using the World Health Organization (WHO) International Classification of Diseases, 9th revision or 10th revision (ICD-9, ICD-10). Air quality measurements included nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter with aerodynamic diameter < or = 10 microm (PM10), and ozone (O3) and were obtained from several fixed-site air monitoring stations that were located throughout the metropolitan areas of the four cities and that met the standards of procedures for quality assurance and quality control carried out by local government units in each city. Using the Common Protocol, an optimized core model was established for each city to assess the effects of each of the four air pollutants on daily mortality using generalized linear modeling with adjustments for time trend, seasonality, and other time-varying covariates by means of a natural-spline smoothing function. The models were adjusted to suit local situations by correcting for influenza activity, autocorrelation, and special weather conditions. Researchers in Hong Kong, for example, used influenza activity based on frequency of respiratory mortality; researchers in Hong Kong and Shanghai used autoregressive terms for daily outcomes at lag days; and researchers in Wuhan used additional smoothing for periods with extreme weather conditions.

RESULTS AND DISCUSSION

For mortality due to all natural (nonaccidental) causes at all ages, the effects of air pollutants per 10-microg/m3 increase in concentration was found to be higher in Bangkok than in the three Chinese cities, with the exception of the effect of NO2 in Wuhan. The magnitude of the effects for cardiovascular and respiratory mortality were generally higher than for all natural mortality at all ages. In addition, the effects associated with PM10 and O3 in all natural, cardiovascular; and respiratory mortality were found to be higher in Bangkok than in the three Chinese cities. The explanation for these three findings might be related to consistently higher daily mean temperatures in Bangkok, variations in average time spent outdoors by the susceptible populations, and the fact that less air conditioning is available and used in Bangkok than in the other cities. However, when pollutant concentrations were incorporated into the excess risk estimates through the use of interquartile range (IQR), the excess risk was more comparable across the four cities. We found that the increases in effects among older age groups were greater in Bangkok than in the other three cities. After excluding data on extremely high concentrations of PM10 in Bangkok, the effect estimate associated with PM10 concentrations decreased in Bangkok (suggesting a convex relationship between risk and PM10, where risk levels off at high concentrations) instead of increasing, as it did in the other cities. This leveling off of effect estimates at high concentrations might be related to differences in vulnerability and exposure of the population to air pollution as well as to the sources of the air pollutant. IMPLICATIONS OF THE STUDY: The PAPA project is the first coordinated Asian multicity air pollution study ever published; this signifies the beginning of an era of cooperation and collaboration in Asia, with the development of a common protocol for coordination, data management, and analysis. The results of the study demonstrated that air pollution in Asia is a significant public health burden, especially given the high concentrations of pollutants and high-density populations in major cities. When compared with the effect estimates reported in the research literature of North America and Western Europe, the study's effect estimates for PM10 were generally similar and the effect estimates for gaseous pollutants were relatively higher. In Bangkok, however, a tropical city where total exposures to outdoor pollution might be higher than in most other cities, the observed effects were greater than those reported in the previous (i.e., Western) studies. In general, the results suggested that, even though social and environmental conditions across Asia might vary, it is still generally appropriate to apply to Asia the effect estimates for other health outcomes from previous studies in the West. The results also strongly support the adoption of the global air quality guidelines recently announced by WHO.

Prenatal and postnatal parental smoking and acute otitis media in early childhood

AIM

To explore the associations between acute otitis media in early childhood and prenatal and postnatal tobacco smoke exposure.

METHODS

Subjects were 32 077 children born between 2000 and 2005 in the Norwegian Mother and Child Study with questionnaire data on tobacco smoke exposure and acute otitis media up to 18 months of age. Multivariate regression models were used to obtain adjusted relative risks for acute otitis media.

RESULTS

Acute otitis media was slightly more common in children exposed to parental smoking. The incidence from 0 to 6 months was 4.7% in unexposed children and 6.0% in children exposed both prenatally and postnatally. After adjusting for postnatal exposure and covariates, the relative risk for acute otitis media 0-6 months when exposed to maternal smoking in pregnancy was 1.34, 95% confidence interval: 1.06-1.69. Maternal smoking in pregnancy was associated with acute otitis media up to 12 months of age. Compared with non-exposed children, there was a slightly increased risk of recurrent acute otitis media for children exposed both prenatally and postnatally with a relative risk of 1.24, 95% confidence interval: 1.01-1.52.

CONCLUSION

Even in a cohort with relatively low exposure levels of parental smoking, maternal smoking in pregnancy was associated with an increased risk of acute otitis media in early childhood.

Pesticide use and adult-onset asthma among male farmers in the Agricultural Health Study

Although specific pesticides have been associated with wheeze in farmers, little is known about pesticides and asthma. Data from 19,704 male farmers in the Agricultural Health Study were used to evaluate lifetime use of 48 pesticides and prevalent adult-onset asthma, defined as doctor-diagnosed asthma after the age of 20 yrs. Asthma cases were categorised as allergic (n = 127) and nonallergic (n = 314) based on their history of eczema or hay fever. Polytomous logistic regression, controlling for age, state, smoking and body mass, was used to assess pesticide associations. High pesticide exposure events were associated with a doubling of both allergic and nonallergic asthma. For ever-use, 12 individual pesticides were associated with allergic asthma and four with nonallergic asthma. For allergic asthma, coumaphos (OR 2.34; 95% CI 1.49-3.70), heptachlor (OR 2.01; 95% CI 1.30-3.11), parathion (OR 2.05; 95% CI 1.21-3.46), 80/20 mix (carbon tetrachloride/carbon disulfide) (OR 2.15; 95% CI 1.23-3.76) and ethylene dibromide (OR 2.07; 95% CI 1.02-4.20) all showed ORs of >2.0 and significant exposure-response trends. For nonallergic asthma, DDT (dichlorodiphenyltrichloroethane) showed the strongest association (OR 1.41; 95% CI 1.09-1.84), but with little evidence of increasing asthma with increasing use. Current animal handling and farm activities did not confound these results. There was little evidence that allergy alone was driving these associations. In conclusion, pesticides may be an overlooked contributor to asthma risk among farmers.

Genetic variation in ORM1-like 3 (ORMDL3) and gasdermin-like (GSDML) and childhood asthma

BACKGROUND

A genome-wide association study identified ORM1-like 3 (orosomucoid 1-like 3, ORMDL3) as an asthma candidate gene. Single nucleotide polymorphisms (SNPs) in the region including ORMDL3 on chromosome 17q21 were related to childhood asthma risk and ORMDL3 expression levels in Europeans.

OBJECTIVE

We examined whether polymorphisms in ORMDL3 and the adjacent gasdermin-like (GSDML) gene associated with asthma in the genome-wide association study are related to childhood asthma and atopy in a Mexico City population.

METHODS

We genotyped rs4378650 in ORMDL3 and rs7216389 in GSDML in 615 nuclear families consisting of asthmatic children aged 4-17 years and their parents. Atopy was determined by skin prick tests to 25 aeroallergens.

RESULTS

Individuals carrying the C allele of rs4378650 or the T allele of rs7216389 had increased risk of asthma [relative risk (RR) = 1.73, 95% confidence interval (CI) 1.19-2.53, P = 0.003 for one or two copies of rs4378650 C, and RR = 1.64, 95% CI 1.12-2.38, P = 0.009 for one or two copies of rs7216389 T). Linkage disequilibrium between the two SNPs was high (r(2) = 0.92). Neither of the SNPs was associated with the degree of atopy. A meta-analysis of five published studies on rs7216389 in nine populations gave an odds ratio for asthma of 1.44 (95% CI, 1.35-1.54, P < 0.00001).

CONCLUSIONS

Our results and the meta-analysis provide evidence to confirm the finding from a recent genome-wide association study that polymorphisms in ORMDL3 and the adjacent GSDML may contribute to childhood asthma.

Dietary fiber, lung function, and chronic obstructive pulmonary disease in the atherosclerosis risk in communities study

Recent data suggest beneficial effects of fiber intake on chronic respiratory symptoms in adults that are independent of antioxidant vitamin intake, but little is known about fiber consumption in relation to lung function and chronic obstructive pulmonary disease (COPD). The authors investigated the association of fiber intake with lung function and COPD in 11,897 US men and women from the Atherosclerosis Risk in Communities study (1987-1989). After control for potential confounders, positive associations were found between lung function and fiber intake from all sources as well as from cereal or fruit alone. Compared with those in the lowest quintile, participants in the highest quintile of total fiber intake had a 60.2-ml higher forced expiratory volume in 1 second (FEV(1)) (p for trend < 0.001), 55.2-ml higher forced vital capacity (FVC) (p = 0.001), 0.4% higher FEV(1)/FVC ratio (p = 0.040), 1.8% higher percent predicted FEV(1) (p < 0.001), and 1.4% higher percent predicted FVC (p = 0.001). Adjusted odds ratios of COPD for the highest versus lowest quintiles of intake were 0.85 (p = 0.044) for total fiber, 0.83 (p = 0.021) for cereal fiber, and 0.72 (p = 0.005) for fruit fiber. This study provides the first known evidence that dietary fiber is independently associated with better lung function and reduced prevalence of COPD.

Childhood exposure to environmental tobacco smoke and chronic respiratory symptoms in non-smoking adults: the Singapore Chinese Health Study

BACKGROUND

Childhood exposure to environmental tobacco smoke has been extensively associated with childhood respiratory illness; fewer studies have addressed the effects on adults.

METHODS

Childhood environmental tobacco smoke exposure in relation to chronic cough, phlegm, and asthma diagnosis was studied in never smokers from a cohort of Singaporeans of Chinese ethnicity aged 45-74 years at enrollment from 1993 to 1998. From 1999 to 2004 subjects were interviewed regarding environmental tobacco smoke exposure before and after the age of 18 and the presence and duration of current symptoms of chronic cough and phlegm production and asthma diagnosis.

RESULTS

Among 35,000 never smokers, fewer had smoking mothers (19%) than fathers (48%). Although few subjects currently lived (20%) or worked (4%) with smokers, 65% reported living with a daily smoker before the age of 18 years. Living with a smoker before the age of 18 increased the odds of chronic dry cough (149 cases, odds ratio 2.1, 95% CI 1.4 to 3.3) and, to a lesser extent, phlegm, after adjustment for age, sex, dialect group, and current and past exposure to smokers at home and at work after the age of 18. Associations strengthened with higher numbers of smokers in childhood. There was no association with asthma or chronic bronchitis. There was evidence to suggest a stronger association among subjects with a lower adult intake of fibre which has previously been found to be protective for respiratory symptoms.

CONCLUSIONS

In this large study of non-smokers, living with a smoker in childhood was associated with chronic dry cough and phlegm in adulthood, independent of later exposures to environmental tobacco smoke.

Genetic polymorphism of GSTM1 and antioxidant supplementation influence lung function in relation to ozone exposure in asthmatic children in Mexico City

BACKGROUND

We recently reported that antioxidant supplementation with vitamins C and E mitigated ozone related decline in forced expiratory flow (FEF(25-75)) in 158 asthmatic children in an area with high ozone exposure in Mexico City.

METHODS

A study was undertaken to determine whether deletion of glutathione S-transferase M1 (GSTM1 null genotype), a gene involved in response to oxidative stress, influences ozone related decline in FEF(25-75) and the benefit of antioxidant supplementation.

RESULTS

GSTM1 null children receiving placebo had significant ozone related decrements in FEF(25-75) (percentage change per 50 ppb of ozone 2.9 (95% CI -5.2 to -0.6), p=0.01); GSTM1 positive children did not. Conversely, the effect of antioxidants was stronger in children with the GSTM1 null genotype.

CONCLUSIONS

Asthmatic children with a genetic deficiency of GSTM1 may be more susceptible to the deleterious effects of ozone on the small airways and might derive greater benefit from antioxidant supplementation.

Animal production and wheeze in the Agricultural Health Study: interactions with atopy, asthma, and smoking

BACKGROUND

Exposure to animals, their feeds, and by-products contribute to respiratory symptoms among farmers.

AIMS

To investigate the role of animal exposures and wheeze, and to assess whether their impact differs among susceptible subgroups, including atopics, asthmatics, and smokers.

METHODS

Using the Agricultural Health Study, a cohort of pesticide applicators in Iowa and North Carolina enrolled in 1994-97, wheeze associated with animal production was evaluated and interactions among susceptible subgroups assessed. Logistic regression models were used to examine risk factors for wheeze in the past year among 20 468 farmers.

RESULTS

Individuals raising animals requiring direct contact had the highest odds ratios (OR) for wheeze (OR(dairy) = 1.26; OR(eggs) = 1.70). A significant dose response was observed for both the number of poultry and the number of livestock on the farm. Farmers who performed veterinary procedures on a daily basis had an OR of 1.51. The odds of wheeze associated with poultry production was greater among atopic than non-atopic individuals. Milking cows daily increased the odds of wheeze in all individuals, with the largest association observed among atopic asthmatic individuals. The impact of dairy, poultry, and egg production varied among smoking groups. Past smokers had the highest odds ratios, followed by never smokers, and then current smokers. The OR(eggs) was 2.88 among past smokers but only 1.46 for never smokers. The OR(eggs) for current smokers of 0.80 might reflect self selection of exposure among smokers.

CONCLUSIONS

Results are consistent with animal production and respiratory symptoms, and suggest that subgroups may respond differently to exposure.

Genetic polymorphism of XRCC1 and lung cancer risk among African-Americans and Caucasians

Reduced DNA repair capacity may influence susceptibility to lung cancer. XRCC1 plays an important role in base excision repair and in rejoining DNA strand breaks. In the XRCC1 gene, two common polymorphisms induce amino acid changes in codon 194 and codon 399 and correlate with levels of genotoxic damage. We examined the relation between these two polymorphisms and susceptibility to lung cancer among 334 incident cases and 704 population controls of African-American and Caucasian ethnicity in Los Angeles County, California. African-American and Caucasian subjects smoking 20+ cigarettes/day and carrying at least one copy of the codon 194 variant allele were at somewhat decreased risk of lung cancer (African-Americans OR=0.2, 95% CI 0.1-0.9; Caucasians OR=0.5, 95% CI 0.2-1.1). Similarly, for the codon 399 polymorphism, there was some evidence of a decreased risk for the homozygous variant genotype among heavier smokers (African-Americans OR=0.3, 95% CI 0.0-2.9; Caucasians OR=0.4, 95% CI 0.2-1.0). These results suggest that genetic variation in XRCC1 might contribute to lung cancer and may interact with the amount smoked.

Respiratory effects of relocating to areas of differing air pollution levels

We studied 110 children (59 boys and 51 girls, who were 10 yr of age at enrollment and 15 yr of age at follow-up) who had moved from communities participating in a 10-yr prospective study of respiratory health (The Children's Health Study [CHS]) to determine whether changes in air quality caused by relocation were associated with changes in annual lung function growth rates. The subjects were given health questionnaires and underwent spirometry in their homes across six western states, according to a protocol identical to evaluations performed annually on the CHS cohort in school. Changes in annual average exposure to particulate matter with a mean diameter of 10 microm (PM(10)) were associated with differences in annual lung function growth rates for FEV(1), maximal midexpiratory flow, and peak expiratory flow rate. As a group, subjects who had moved to areas of lower PM(10) showed increased growth in lung function and subjects who moved to communities with a higher PM(10) showed decreased growth in lung function. A stronger trend was found for subjects who had migrated at least 3 yr before the follow-up visit than for those who had moved in the previous 1 to 2 yr. We conclude that changes in air pollution exposure during adolescent growth years have a measurable and potentially important effect on lung function growth and performance.

Collection of buccal cell DNA in seventh-grade children using water and a toothbrush

We developed a simple and effective method for collecting a large quantity of buccal cell DNA in school-based studies of seventh-grade and older children. Seventh-grade students at schools in Wuhan, China brushed each buccal surface with a soft toothbrush and then rinsed with 10 ml of water. We added 5 ml of 99% ethanol to preserve the sample. Among 1563 samples transported at room temperature over 1 week and then stored for 13-14 months at -70 degrees C before extraction, using a modified Gentra Puregene protocol, the median total DNA yield was 108 microg, range of 14 to 416 microg. We assayed every 20th sample (n = 77) for NAT2 by the PCR, and all samples gave a 1093-bp product. From the 1563 samples, we obtained a result for single nucleotide polymorphisms in the interleukin-13 gene (at +2044) by RFLP-PCR on 98.8% and in the promoter of the myeloperoxidase gene (at -463) by real-time PCR on 99.7%. A water-rinse method, that we used among 12th-grade students in Southern California, gave a lower total DNA yield than the toothbrush rinse (median of 17 microg) and a slightly reduced ability to generate a PCR product. However, 26 of 27 water-rinse samples gave a result for two genes, albumin and CYP1A1, using real-time PCR methods. We did not quantify human, versus bacterial, DNA in our samples. However, given the amounts of total DNA required for genotyping, a sample with the median yield of 108 microg should suffice for approximately 2160 genotypes by RFLP-PCR methods or five times as many by real-time PCR. We recommend the toothbrush-rinse method, combined with a modified Gentra Puregene DNA extraction protocol, for large-scale, in-person collections of buccal cell DNA in children. The method requires only inexpensive, readily available materials and produces a large quantity of high-quality DNA for PCR analyses.

Family history and the risk of early-onset persistent, early-onset transient, and late-onset asthma

Family history of asthma and allergies strongly influences asthma risk in children, but the association may differ for early-onset persistent, early-onset transient, and late-onset asthma. We analyzed the relation between family history and these types of asthma using cross-sectional data from a school-based study of 5,046 Southern California children. Parental and/or sibling history of asthma and allergy were generally more strongly associated with early-onset persistent asthma compared with early-onset transient or late-onset asthma. For children with two asthmatic parents relative to those with none, the prevalence ratio for early-onset persistent asthma was 12.1 [95% confidence interval (CI) = 7.91-18.7] compared with 7.51 (95% CI = 2.62-21.5) for early-onset transient asthma and 5.38 (95% CI = 3.40-8.50) for late-onset asthma. Maternal smoking in pregnancy was predominantly related to the risk of early-onset persistent asthma in the presence of parental history of allergy and asthma, and the joint effects were more than additive (interaction contrast ratio = 3.10, 95% CI = 1.45-4.75). Our results confirm earlier data that parental history of asthma and allergy is most strongly associated with early-onset persistent asthma and suggest that among genetically predisposed children, an early-life environmental exposure, maternal smoking during pregnancy, favors the development of early-onset asthma that persists into later early childhood.

CTNNB1 mutations and beta-catenin protein accumulation in human hepatocellular carcinomas associated with high exposure to aflatoxin B1

beta-Catenin plays a key role in the Wnt signaling pathway, and mutations of CTNNB1, the gene that encodes beta-catenin, have been identified in about one-fourth of human hepatocellular carcinomas from regions of low aflatoxin B1 exposure. In this study 62 hepatocellular carcinomas (HCCs) from people highly exposed to aflatoxin B1 in Guangxi, People's Republic of China, were laser-capture microdissected and examined for CTNNB1 mutations. In addition, 41 of the HCCs were evaluated for the presence of the beta-catenin protein by immunohistochemical methods. Twenty of the HCCs showed positive results for beta-catenin, with strong membrane staining, while adjacent non-neoplastic liver tissue lacked or showed only weak membrane staining. One HCC, in which a CTNNB1 mutation was not detected, showed nuclear staining for the beta-catenin protein. Mutations of CTNNB1 were identified in five HCCs. These consisted of four point mutations in the glycogen serine kinase-3beta phosphorylation region of codons 32-45 and one deletion of codons 32-38. These mutations were similar to those previously reported for human HCC, although at a lower frequency. A signature mutation profile associated with aflatoxin B1 exposure could not be identified. The immunohistochemical findings indicate a role for accumulation of beta-catenin and possibly increased Wnt signaling in aflatoxin B1-associated HCC. The low frequency of CTNNB1 mutations, however, suggests that mutation of another Wnt signaling component, such as the Wnt scaffolding protein axin or the adenomatous polyposis coli protein, both of which modulate beta-catenin stability, also may be involved in aflatoxin-associated HCC. Published 2001 Wiley-Liss, Inc.

Hepatitis B, aflatoxin B(1), and p53 codon 249 mutation in hepatocellular carcinomas from Guangxi, People's Republic of China, and a meta-analysis of existing studies

The incidence of hepatocellular carcinomas (HCC) varies widely worldwide, with some of the highest incidence rates found in China. Chronic infection with the hepatitis B virus (HBV) and exposure to aflatoxins in foodstuffs are the main risk factors. A G to T transversion at codon 249 of the p53 gene (249(ser)) is commonly found in HCCs from patients in regions with dietary aflatoxin exposure. Because HBV infection is often endemic in high aflatoxin exposure areas, it is still unclear whether HBV acts as a confounder or as a synergistic partner in the development of the 249(ser) p53 mutation. Our report has two aims. First, we contribute data on HCCs from southern Guangxi, a high aflatoxin exposure area. Using DNA sequencing, we found that 36% (18 of 50) of tumors had a 249(ser) mutation. Also, 50% (30 of 60) were positive for p53 protein accumulation and 78% (28 of 36) were positive for HBV surface antigen, as detected by immunohistochemistry. Second, we present a meta-analysis, using our results along with those from 48 published studies, that examines the interrelationships among aflatoxin exposure, HBV infection, and p53 mutations in HCCs. We used a method that takes into account both within-study and study-to-study variability and found that the mean proportion of HCCs with the 249(ser) mutation was positively correlated with aflatoxin exposure (P = 0.0001). We found little evidence for an HBV-aflatoxin interaction modulating the presence of the p53 249(ser) mutation or any type of p53 mutation.

The effects of ambient air pollution on school absenteeism due to respiratory illnesses

We investigated the relations between ozone (O3), nitrogen dioxide (NO2), and respirable particles less than 10 microm in diameter (PM10) and school absenteeism in a cohort of 4th-grade school children who resided in 12 southern California communities. An active surveillance system ascertained the numbers and types of absences during the first 6 months of 1996. Pollutants were measured hourly at central-site monitors in each of the 12 communities. To examine acute effects of air pollution on absence rates, we fitted a two-stage time-series model to the absence count data that included distributed lag effects of exposure adjusted for long-term pollutant levels. Short-term change in O3, but not NO2 or PM10, was associated with a substantial increase in school absences from both upper and lower respiratory illness. An increase of 20 ppb of O3 was associated with an increase of 62.9% [95% confidence interval (95% CI) = 18.4-124.1%] for illness-related absence rates, 82.9% (95% CI = 3.9-222.0%) for respiratory illnesses, 45.1% (95% CI = 21.3-73.7%) for upper respiratory illnesses, and 173.9% (95% CI = 91.3-292.3%) for lower respiratory illnesses with wet cough. The short-term effects of a 20-ppb change of O3 on illness-related absenteeism were larger in communities with lower long-term average PM10 [223.5% (95% CI = 90.4-449.7)] compared with communities with high average levels [38.1% (95% CI = 8.5-75.8)]. Increased school absenteeism from O3 exposure in children is an important adverse effect of ambient air pollution worthy of public policy consideration.

Sex-specific effects of asthma on pulmonary function in children

To evaluate the effects on lung function of asthma, time since diagnosis of asthma, and age at diagnosis of asthma, we examined school children in a cohort of 2,277 fourth- and seventh-graders at least twice during a 4-yr follow-up period. Sex-specific models for each lung function were fitted through mixed-effects models that used regression splines and captured age-dependent trends in the effect of asthma on lung function. In males, a history of asthma was associated with large and statistically significant deficits in maximum midexpiratory flow (MMEF) (-4.89%) and forced expiratory flow at 75% of expired FVC (FEF(75)) (-6.62%), whereas in females these deficits were smaller (-1.93% and -2.45%, respectively) and were not statistically significant. However, larger deficits were seen in both males and females with longer time since diagnosis. In males with more than 6 yr since diagnosis, there were significant deficits in FEV(1) (-3.91%), MMEF (-7.39%), FEF(75) (-8.12%), and peak expiratory flow rate (PEFR) (-4.65%) as compared with children with less than 3 yr since diagnosis. There were fewer females with more than 6 yr since diagnosis, but deficits were similar to those of males for FEV(1) (-2.52%), MMEF (-9.26%), and FEF(75) (-14.28%). Large deficits in flow rates in both large and small airways were observed in males and females for whom asthma was reported to have been diagnosed before age 3 yr. There was little evidence that lung growth in children with asthma "catches up" at older ages. Therefore, because a constant percent deficit in lung function implies an increasingly large absolute deficit in older children with larger lungs, these results are consistent with prior evidence that lung function deficits in children with asthma persist into adulthood. We also suggest that in children, commonly observed differences between sexes in the impact of asthma on lung function may reflect differences in the duration and age of onset of asthma in males and females.

CYP1A1 I462V genetic polymorphism and lung cancer risk in a cohort of men in Shanghai, China

Cytochrome P450 (CYP) CYP1A1 activates tobacco-related carcinogens. A point mutation at codon 462 in exon 7 of CYP1A1 results in a substitution of isoleucine by valine near the heme binding site. This mutation is rare in Caucasians but common in Japanese populations, in which association with increased risk of lung cancer has been reported. There are few data in other Asian populations. We investigated this I462V polymorphism using DNA from 214 incident cases of lung cancer and 669 controls in a prospective cohort study of 18,244 middle-aged and older men in Shanghai, China. The valine allele frequency was 0.138 among the control population. The I462V genotype was not appreciably associated with lung cancer risk overall. There was some suggestion that having at least one valine allele might be related to increased risk of lung cancer among smokers of <20 cigarettes/day (odds ratio, 1.72; 95% confidence interval, 0.82-3.62), particularly among those with homozygous deletion of GSTM1 (odds ratio, 2.80; 95% confidence interval, 1.07-7.33), which is involved in the detoxification of activated tobacco carcinogens. In this Chinese cohort, with CYP1A1 valine allele frequency intermediate between Japanese and Caucasian populations, the I462V polymorphism is not related to lung cancer overall, but it might play a role at lower levels of cigarette smoking among subjects with impaired carcinogen detoxification as assessed by the GSTM1-null genotype.

Isothiocyanates, glutathione S-transferase M1 and T1 polymorphisms, and lung-cancer risk: a prospective study of men in Shanghai, China

BACKGROUND

Dietary isothiocyanates inhibit lung carcinogenesis in laboratory animals but human data are limited. Glutathione S-transferases M1 and T1 (GSTM1 and GSTT1) conjugate isothiocyanates leading to more rapid elimination. Common deletion polymorphisms of GSTM1 and GSTT1 abolish enzyme activity. We hypothesised that chemopreventive effects of isothiocyanates might be heightened when enzymes that enhance their elimination are lacking.

METHODS

We examined the relation between total isothiocyanate concentrations in urine, collected before diagnosis, and the subsequent risk of lung cancer among 232 incident cases of lung cancer and 710 matched controls from a cohort of 18,244 men in Shanghai, China, followed from 1986 to 1997. Homozygous deletion of the GSTM1 and GSTT1 genes were determined by PCR.

FINDINGS

Individuals with detectable isothiocyanates in the urine were at decreased risk of lung cancer (smoking-adjusted relative risk for lung cancer=0.65 [95% CI 0.43-0.97]). This protective effect of isothiocyanates was seen primarily among individuals with homozygous deletion of GSTM1 (0.36 [0.20-0.63]) and particularly with deletion of both GSTM1 and GSTT1 (0.28 [0.13-0.57]).

INTERPRETATION

Isothiocyanates appeared to reduce lung-cancer risk in this cohort of Chinese men. Reduction in risk was strongest among persons genetically deficient in enzymes that rapidly eliminate these chemopreventive compounds.

Quantification of (7S,8R)-dihydroxy-(9R,10S)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene adducts in human serum albumin by laser-induced fluorescence: implications for the in vivo metabolism of benzo[a]pyrene

The ubiquitous environmental carcinogen benzo[a]pyrene (BaP) is metabolized in vivo in humans to its ultimate carcinogenic form of 7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). Mouse skin tumorigenicity studies indicate that the (7R,8S,9S,10R) enantiomer of BPDE, (7R,8S)-dihydroxy-(9S,10R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(7R,8S,9S,10R)-BPDE], is a potent tumor initiator, whereas the (7S,8R,9R,10S) enantiomer of BPDE, (7S,8R)-dihydroxy-(9R,10S)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(7S,8R,9R,10S)-BPDE], may act as a tumor promoter. In vitro experiments have shown that human liver microsomes are capable of metabolizing BaP to both the (7R,8S,9S,10R) and (7S,8R,9R,10S) enantiomers of BPDE. However, the metabolism of BaP to (7S,8R,9R,10S)-BPDE has not been demonstrated in humans in vivo. The adducts formed between human serum albumin (HSA) and the (7S,8R,9R,10R) and (7R,8S,9S,10R) enantiomers of BPDE have been described previously. (7S,8R,9R,10S)-BPDE forms a stable adduct at histidine146 of HSA, whereas (7R,8S,9R,10R)-BPDE forms a relatively unstable ester adduct at aspartate187 or glutamate188 of HSA. Using high-performance liquid chromatography with laser-induced fluorescence (LIF) detector, we quantified the level of (7S,8R,9R,10S)-BPDE adducts at histidine146 in HSA isolated from 63 healthy males who were population control subjects for an ongoing case-control study of bladder cancer. By design, roughly half of the participants were lifelong nonsmokers (n = 35), whereas the remaining 28 participants were current smokers of varying intensities. HP-BPDE adducts were detected in 60 of the 63 samples (95%) by HPLC-LIF. Adduct levels ranged from undetectable (<0.04 fmol/mg HSA) to 0.77 fmol/mg HSA. The samples had a mean and median (7S,8R,9R,10S)-BPDE-HSA adduct level of 0.22 and 0.16 fmol of adduct/mg albumin, respectively. Mean adduct levels did not differ between smokers and nonsmokers (P = 0.72). Occupational exposure to polycyclic aromatic hydrocarbons was unrelated to adduct level (P = 0.62). Intake frequencies of two food items showed statistically significant associations with adduct levels. Consumption of sweet potatoes was negatively related to adduct level (P = 0.029), whereas intake of grapefruit juice was positively related to adduct level (P = 0.045). None of the three indices of residential ambient air pollution under study showed a statistically significant association with adduct levels.

Lung cancer risk in relation to genetic polymorphisms of microsomal epoxide hydrolase among African-Americans and Caucasians in Los Angeles County

Microsomal epoxide hydrolase participates in the metabolism of benzo[a]pyrene, an important carcinogen in tobacco smoke. Two relatively common polymorphisms of the microsomal epoxide hydrolase gene that influence enzyme activity have been described. An association between genetic variation in microsomal epoxide hydrolase and lung cancer risk has been reported in one of two studies of Caucasians. We examined the relation between these two polymorphisms and lung cancer risk among 337 incident cases and 700 population controls of African-American and Caucasian ethnicity enrolled in a case-control study in Los Angeles County. African-Americans, homozygous for the exon 3 variant allele conferring reduced activity, were at decreased risk of lung cancer (odds ratio (OR)=0.08, 95% CI 0.01-0.62). When data from both the exon 3 and exon 4 polymorphisms were combined into indices of predicted microsomal epoxide hydrolase activity, a decreased risk was seen among African-American subjects with very low predicted activity OR=0.10 (95% CI 0.01-0.83). No comparable association was seen among Caucasians. Although the three published results for Caucasians are somewhat variable, the association among African-Americans in these data provides some support for the hypothesis that genetically reduced microsomal epoxide hydrolase activity may be protective against lung cancer.

Air pollution and bronchitic symptoms in Southern California children with asthma

The association of air pollution with the prevalence of chronic lower respiratory tract symptoms among children with a history of asthma or related symptoms was examined in a cross-sectional study. Parents of a total of 3,676 fourth, seventh, and tenth graders from classrooms in 12 communities in Southern California completed questionnaires that characterized the children's histories of respiratory illness and associated risk factors. The prevalences of bronchitis, chronic phlegm, and chronic cough were investigated among children with a history of asthma, wheeze without diagnosed asthma, and neither wheeze nor asthma. Average ambient annual exposure to ozone, particulate matter (PM(10) and PM(2.5); [less than/equal to] 10 microm and < 2.5 microm in aerodynamic diameter, respectively), acid vapor, and nitrogen dioxide (NO(2)) was estimated from monitoring stations in each community. Positive associations between air pollution and bronchitis and phlegm were observed only among children with asthma. As PM(10) increased across communities, there was a corresponding increase in the risk per interquartile range of bronchitis [odds ratio (OR) 1.4/19 microg/m(3); 95% confidence interval (CI), 1.1-1.8). Increased prevalence of phlegm was significantly associated with increasing exposure to all ambient pollutants except ozone. The strongest association was for NO(2), based on relative risk per interquartile range in the 12 communities (OR 2.7/24 ppb; CI, 1.4-5.3). The results suggest that children with a prior diagnosis of asthma are more likely to develop persistent lower respiratory tract symptoms when exposed to air pollution in Southern California.

A study of twelve Southern California communities with differing levels and types of air pollution. I. Prevalence of respiratory morbidity

To study possible chronic respiratory effects of air pollutants, we initiated a 10-yr prospective cohort study of Southern California children, with a study design focused on four pollutants: ozone, particulate matter, acids, and nitrogen dioxide (NO2). Twelve demographically similar communities were selected on the basis of historic monitoring information to represent extremes of exposure to one or more pollutants. In each community, about 150 public school students in grade 4, 75 in grade 7, and 75 in grade 10 were enrolled through their classrooms. Informed consent and written responses to surveys about students' lifetime residential histories, historic and current health status, residential characteristics, and physical activity were obtained with the help of the parents. In the first testing season, 3,676 students returned questionnaires. We confirmed associations previously reported between respiratory morbidity prevalence and the presence of personal, demographic, and residential risk factors. Rates of respiratory illness were higher for males, those living in houses with pets, pests, mildew, and water damage, those whose parents had asthma, and those living in houses with smokers. Wheeze prevalence was positively associated with levels of both acid (odds ratio [OR] = 1.45; 95% confidence interval [CI], 1.14-1.83) and NO2 (OR = 1.54; 95% CI, 1.08-2.19) in boys. We conclude, based on this cross-sectional assessment of questionnaire responses, that current levels of ambient air pollution in Southern California may be associated with effects on schoolchildren's respiratory morbidity as assessed by questionnaire.

A study of twelve Southern California communities with differing levels and types of air pollution. II. Effects on pulmonary function

To study the possible chronic respiratory effects of air pollutants, we designed and initiated a 10-yr prospective study of Southern California public schoolchildren living in 12 communities with different levels and profiles of air pollution. The design of the study, exposure assessment methods, and survey methods and results related to respiratory symptoms and conditions are described in the accompanying paper. Pulmonary function tests were completed on 3,293 subjects. We evaluated cross-sectionally the effects of air pollution exposures based on data collected in 1986-1990 by existing monitoring stations and data collected by our study team in 1994. Expected relationships were seen between demographic, physical, and other environmental factors and pulmonary function values. When the data were stratified by sex, an association was seen between pollution levels and lower pulmonary function in female subjects, with the associations being stronger for the 1994 exposure data than the 1986-1990 data. After adjustment, PM10, PM2.5, and NO2 were each significantly associated with lower FVC, FEV1, and maximal midexpiratory flow (MMEF); acid vapor with lower FVC, FEV1, peak expiratory flow rate (PEFR), and MMEF; and O3 with lower PEFR and MMEF. Effects were generally larger in those girls spending more time outdoors. Stepwise regression of adjusted pulmonary function values for girls in the 12 communities showed that NO2 was most strongly associated with lower FVC (r = -0.74, p < 0.01), PM2.5 with FEV1 (r = -0.72, p < 0.01), O3 with PEFR (r = -0.75, p < 0.005), and PM2.5 with MMEF (r = -0.80, p < 0.005). There was a statistically significant association between ozone exposure and decreased FVC and FEV1 in girls with asthma. For boys, significant associations were seen between peak O3 exposures and lower FVC and FEV1, but only in those spending more time outdoors. These findings underline the importance of follow-up of this cohort.

A study of twelve Southern California communities with differing levels and types of air pollution. I. Prevalence of respiratory morbidity

To study possible chronic respiratory effects of air pollutants, we initiated a 10-yr prospective cohort study of Southern California children, with a study design focused on four pollutants: ozone, particulate matter, acids, and nitrogen dioxide (NO2). Twelve demographically similar communities were selected on the basis of historic monitoring information to represent extremes of exposure to one or more pollutants. In each community, about 150 public school students in grade 4, 75 in grade 7, and 75 in grade 10 were enrolled through their classrooms. Informed consent and written responses to surveys about students' lifetime residential histories, historic and current health status, residential characteristics, and physical activity were obtained with the help of the parents. In the first testing season, 3,676 students returned questionnaires. We confirmed associations previously reported between respiratory morbidity prevalence and the presence of personal, demographic, and residential risk factors. Rates of respiratory illness were higher for males, those living in houses with pets, pests, mildew, and water damage, those whose parents had asthma, and those living in houses with smokers. Wheeze prevalence was positively associated with levels of both acid (odds ratio [OR] = 1.45; 95% confidence interval [CI], 1.14-1.83) and NO2 (OR = 1.54; 95% CI, 1.08-2.19) in boys. We conclude, based on this cross-sectional assessment of questionnaire responses, that current levels of ambient air pollution in Southern California may be associated with effects on schoolchildren's respiratory morbidity as assessed by questionnaire.

Mentholated cigarette smoking and lung-cancer risk

PURPOSE

Menthol smoking may lead to a greater increase in lung-cancer risk than smoking of nonmentholated cigarettes. Mentholation of cigarettes adds additional carcinogenic components to cigarette smoke and increases retention times for cigarette smoke in the lungs. Only two epidemiologic studies have been conducted on menthol smoking and lung cancer, and their results are conflicting. Of note, African American males have much higher rates of lung cancer than Caucasian males despite smoking fewer cigarettes per day. Because the consumption of menthol cigarettes is much more frequent among African Americans, it is of interest to examine the possible association between menthol smoking and lung-cancer risk in this population.

METHODS

We examined the association between menthol cigarette smoking and lung-cancer risk among smokers by comparing 337 incident cases of lung cancer with 478 population controls enrolled in a case-control study of lung cancer. Information on smoking history and other known and potential risk factors for lung cancer, including dietary intake, was obtained by in-person interviews.

RESULTS

The adjusted odds ratios did not differ appreciably between smokers of mentholated cigarettes versus exclusive nonmentholated cigarette smokers in the overall study group of smokers. The odds ratio (OR) for 32 pack-years or more of mentholated vs. nonmentholated cigarettes was 0.90 (95% confidence interval (CI) = 0.38-2.12) in African Americans and 1.06 (95% CI = 0.47-2.36) in Caucasians, and did not differ for either ethnic group (p = 0.98).

CONCLUSIONS

Our results suggest that the lung-cancer risk from smoking mentholated cigarettes resembles the risk from smoking non-mentholated cigarettes. Our data do not support the hypothesis that the increased risk of lung cancer among African Americans is due to the increased prevalence of menthol smoking.

CYP2D6 phenotype-genotype relationships in African-Americans and Caucasians in Los Angeles

CYP2D6 genotyping (CYP2D6*3, CYP2D6*4, CYP2D6*5, CYP2D6*13, CYP2D6*16 alleles and gene duplications) was previously performed on 1053 Caucasian and African-American lung cancer cases and control individuals and no significant difference in allele frequencies between cases and control individuals detected. We have carried out additional genotyping (CYP2D6*6, CYP2D6*7, CYP2D6*8, CYP2D6*9, CYP2D6*10, CYP2D6*17 alleles) and debrisoquine phenotyping on subgroups from this study to assess phenotype-genotype relationships. African-Americans showed significant differences from Caucasians with respect to frequency of defective CYP2D6 alleles, particularly CYP2D6*4 and CYP2D6*5. The CYP2D6*17 allele occurred at a frequency of 0.26 among 87 African-Americans and appeared to explain higher average metabolic ratios among African-Americans compared with Caucasians. CYP2D6*6, CYP2D6*8, CYP2D6*9 and CYP2D6*10 were rare in both ethnic groups but explained approximately 40% of higher than expected metabolic ratios among extensive metabolizers. Among individuals phenotyped with debrisoquine, 32 out of 359 were in the poor metabolizer range with 24 of these (75%) also showing two defective CYP2D6 alleles. Additional single strand conformational polymorphism analysis screening of samples showing large phenotype-genotype discrepancies resulted in the detection of three novel polymorphisms. If subjects taking potentially interfering drugs were excluded, this additional screening enabled the positive identification of 88% of phenotypic poor metabolizers by genotyping. This sensitivity was comparable with that of phenotyping, which identified 90% of those with two defective alleles as poor metabolizers.

Alcoholic beverage consumption and lung cancer risk among residents of Los Angeles County

Although studies generally support a positive association between alcohol consumption and lung-cancer risk, the relationship between specific alcoholic beverages and lung-cancer risk has been inconsistent. We examined recent and past alcoholic beverage intake among 261 incident cases and 615 population controls enrolled in a lung-cancer case-control study of African Americans and Caucasians in Los Angeles County between 1991 and 1994. An in-person interview elicited information about past alcohol intake from ages 30 to 40 y, smoking, other lung-cancer risk factors, as well as recent intake of alcohol, and recent dietary intake. An association was observed between recent hard-liquor consumption and lung-cancer risk. The odds ratio (OR) for 1 or more drinks (1.5 oz or 0.051 mL) per day of hard liquor compared with infrequent liquor drinking (0-3 drinks per month), adjusted for smoking, the matching factors, saturated fat and other alcoholic beverages was 1.87 [95% confidence interval (CI) = 1.02-3.42]. No appreciable association was observed for total alcohol, whereas small inverse associations were observed for beer and wine, although confidence intervals were wide. An elevated lung-cancer risk was also observed for past liquor consumption (between ages 30 and 40 y). The adjusted OR for 1 or more drinks per day of liquor compared with infrequent drinkers was 1.83 (95% CI = 1. 06-3.15). Confounding of the association between alcohol and lung cancer by smoking was apparent. Although we devoted considerable efforts to adjusting for smoking in our analyses, residual confounding is still possible because smoking and alcohol are closely associated. In addition, case-control studies including this study should be viewed with caution because of possible selection bias. An increased risk of lung cancer might occur with moderate drinking of hard liquor but confirmation is required in larger studies.

Myeloperoxidase genetic polymorphism and lung cancer risk

Myeloperoxidase is a lysosomal enzyme found in high concentrations in human lung due to recruitment of neutrophils. Myeloperoxidase activates benzo[a]pyrene as well as aromatic amines in tobacco smoke and generates carcinogen-free radicals. A single base substitution (G to A) in the promoter region of the myeloperoxidase gene has recently been demonstrated to markedly reduce transcription. We developed an RFLP/PCR assay to test the hypothesis that the allele favoring lower transcription (A allele) reduces the risk of lung cancer. Among population controls, 7.8% of 459 Caucasians and 9.4% of 244 African-Americans inherited two copies of the A allele. Caucasians with the A/A genotype were at 70% reduced risk of lung cancer (odds ratio, 0.30; 95% confidence interval, 0.10-0.93; P = 0.04; 182 cases). A lesser reduction in risk was observed for African-Americans with this genotype (odds ratio, 0.61; 95% confidence interval, 0.26-1.41; 157 cases). Individuals who inherit two copies of an allele that reduces transcription of the myeloperoxidase gene may be at decreased risk of lung cancer.

Leukemia risk and occupational electric field exposure in Los Angeles County, California

The authors analyzed data on electric fields from a prior study of occupational magnetic field exposure and leukemia risk conducted in Los Angeles County, California, in 1972-1990. Ranking of exposure differed somewhat for magnetic and electric fields. The odds ratios were 1.22 (95% confidence interval (CI) 0.80-1.86) and 1.15 (95% confidence interval 0.78-1.72) for medium and high exposure categories, respectively, and there was no clear evidence of an exposure-response relation (odds ratio for 10 V/m increase = 1.05, 95% CI 0.95-1.16). Although not conclusive, our analyses provide little support for an association between occupational electric field exposure and leukemia.

Genetic polymorphism of CYP2D6 and lung cancer risk in African-Americans and Caucasians in Los Angeles County

The well described genetic polymorphism of the CYP2D6 gene influences response to a wide variety of therapeutic agents metabolized by the CYP2D6 enzyme product. CYP2D6 also appears to play a role, along with other cytochrome P450 enzymes, in the metabolic activation of the tobacco specific nitrosamine, NNK, as well as metabolism of nicotine to cotinine. While impaired activity of CYP2D6 was strongly protective against lung cancer in some studies, primarily based on phenotyping, the literature is conflicting. The molecular basis of CYP2D6 deficiency is now well understood, enabling the use of genotyping to classify individuals. We therefore examined whether lung cancer risk is reduced by the presence of four CYP2D6 alleles associated with impaired activity due to an inactivating mutation--CYP2D6*4, CYP2D6*3, CYP2D6*5 and CYP2D6*16--among 341 incident cases of lung cancer and 710 population controls of Caucasian or African-American ethnicity in Los Angeles County, California. We did not confirm a strong association between the presence of these inactivating alleles and lung cancer risk [odds ratio (OR) = 0.90, 95% confidence interval (CI) 0.60-1.35 for Caucasians], although there was a small decreased risk among the African-Americans (OR = 0.66, 95% CI 0.38-1.14). Among smokers, when the data are stratified according to lifetime smoking history, there is a suggestion of an association limited to Caucasian smokers of <35 pack-years, the median for all smokers in these data (OR = 0.49, 95% CI 0.23-1.04). However, among African-American smokers, who smoke less than Caucasians, the association did not differ between smoking categories. We also examined the possible role of additional copies of the CYP2D6 gene, which lead to enhanced CYP2D6 activity, in increasing lung cancer risk. Among controls the prevalence of having more than two copies of the CYP2D6 gene and no inactivating alleles was 4.3% for Caucasians and 4.9% for African-Americans. Relative to subjects with an inactivating allele, those with an additional copy of the CYP2D6 gene and no inactivating alleles may be at increased risk of lung cancer, particularly for adenocarcinoma (OR = 3.61, 95% CI 1.08-11.7 for African-Americans and OR = 2.20, 95% CI 0.69-6.0 for Caucasians). Our data suggest that the CYP2D6 genetic polymorphism is not the strong risk factor for lung cancer suggested by some studies of phenotype, but may play a minor role.

Risk of breast cancer associated with atypical hyperplasia of lobular and ductal types

Epidemiological studies using the histological classification of Page for benign breast disease consistently demonstrate a positive association between atypical hyperplasia and the subsequent development of breast cancer. However, atypical hyperplasia is of either lobular or ductal types, and breast cancer risk in relation to type of atypical hyperplasia has not been studied extensively. Thus, we investigated prospectively the risk of breast cancer associated with histological subtypes of benign proliferative breast disease, including the types of atypical hyperplasia, among participants in the Nurses' Health Study who had biopsy-confirmed benign breast disease. Women who subsequently developed breast cancer were matched by year of birth and year of biopsy to participants who were free from breast cancer. Benign biopsy slides were classified according to the criteria of Page. Odds ratios (ORs) of breast cancer and 95% confidence intervals (CIs), adjusted for the matching variables and other breast cancer risk factors, were computed using unconditional logistic regression with benign nonproliferative breast disease as the referent group. Atypical ductal hyperplasia (OR = 2.4; 95% CI, 1.3-4.5) or atypical lobular hyperplasia (OR = 5.3; 95% CI, 2.7-10.4) in a prior biopsy were associated with increased breast cancer risk. Atypical lobular hyperplasia was more strongly associated with the risk of premenopausal breast cancer (OR = 9.6; 95% CI, 3.3-27.8) than with the risk of postmenopausal breast cancer (OR = 3.7; 95% CI, 1.3-10.2). The association of atypical ductal hyperplasia and breast cancer risk varied little by menopausal status. The magnitude of breast cancer risk seems to vary according to the type of atypical hyperplasia present at biopsy.

Lung cancer risk in relation to the CYP2C9*1/CYP2C9*2 genetic polymorphism among African-Americans and Caucasians in Los Angeles County, California

CYP2C9 is involved in the metabolism of warfarin and a wide array of other therapeutic agents. It also appears to play a role, along with other cytochrome P450 enzymes, in the metabolism of benzo[a]pyrene, a carcinogen in tobacco smoke. A relatively common allelic variant (termed R144C, Cys144 or more recently CYP2C9*2) has been described that results in the substitution of cysteine for arginine at residue 144 and appears to reduce enzyme activity. We therefore examined the possible association between the presence of the CYP2C9*2 variant allele and risk of lung cancer using peripheral blood DNA from 329 incident cases of lung cancer (152 African-American and 177 Caucasian) and 700 (239 African-American and 461 Caucasian) population controls in Los Angeles County, California. Among the population controls the frequency of the CYP2C9*2 variant allele was lower (p = 0.00002) among African-Americans (0.036) than among Caucasians (0.100). The presence of the CYP2C9*2 variant allele was not associated with a decreased risk of lung cancer; slight but nonstatistically significant elevations in risk were observed for both African-Americans [odds ratio (OR) 1.22, 95% confidence interval (CI) 0.48-3.11] and Caucasians (OR = 1.55, 95% CI 0.96-2.48). The ORs were slightly and nonsignificantly elevated for all histologic types without substantive variation. The association also did not vary materially according to smoking history or whether subjects had the homozygous deletion of the GSTM1 gene. We found no support for the hypothesis that the CYP2C9*2 variant allele decreases the risk of lung cancer. The role of P450s, including CYP2C9, in benzo[a]pyrene metabolism is not fully defined, and CYP2C9 catalyses detoxication as well as activation steps. Thus it is not inconceivable that diminished CYP2C9 activity could increase metabolic activation of benzo[a]pyrene to carcinogenic intermediates. Nonetheless, the small increased risk associated the CYP2C9*2 variant allele in our data is consistent with chance and should not be overinterpreted.

Characterization and PCR-based detection of two different hybrid CYP2D7P/CYP2D6 alleles associated with the poor metabolizer phenotype

The majority of humans deficient in the cytochrome P450 CYP2D6 enzyme, so-called poor metabolizers (PMs), can now be identified by genotyping for several different PM-associated mutations. However, additional null alleles remain to be identified as demonstrated by subjects with the PM phenotype in the absence of a corresponding genotype. The rare 11 kb band on Xba I RFLP analysis, which is distinct from the 13 kb CYP2D6D (CYP2D6*5) allele, has been proposed to constitute such a unique non-functional allele. Here we demonstrate that the 11 kb band represents at least two different nine exon CYP2D7P/CYP2D6 hybrids generated by large deletions in the CYP2D gene cluster due to unequal cross-over or looping-out mechanisms. The total allele frequency was approximately 0.001-0.01 in European and North American Caucasians. The most common variant (CYP2D6*16) had breakpoints lying between the end of exon 7 and the start of exon 9 of the respective genes. The "CYP2D7-like' part of the gene was most homologous to the previously described CYP2D7AP and CYP2D7 (44/11.5) sequences. The other chimeric allele consisted of exon 1 of CYP2D7 and exons 2-9 from CYP2D6, and may be similar to a hybrid gene termed CYP2D6*13 recently described in a French individual. Two different routine PCR assays were developed for rapid and sensitive detection of these alleles, namely amplification of a 8 kb fragment from both CYP2D6*13 and CYP2D6*16, together with a CYP2D6*16-specific method which gave a 1.4 kb PCR product. The 8 kb assay for the CYP2D6*13 and CYP2D6*16 alleles also produced a 9.5 kb fragment in samples positive for the 13 kb CYP2D6*5 allele. Therefore, it is now possible to screen for the large CYP2D gene deletions by a single long PCR method.

Lung cancer risk in relation to the CYP2E1 Rsa I genetic polymorphism among African-Americans and Caucasians in Los Angeles County

Genetic polymorphisms in the activation or detoxication of carcinogens, such as those in tobacco smoke, may produce differences in individual susceptibility to lung cancer. The cytochrome P450 CYP2E1 is an enzyme involved in the metabolism of nitrosamines in tobacco smoke. A polymorphism of CYP2E1 detectable by the restriction enzyme Rsa I may be functionally important because it is located in a putative binding site for the transcription factor HNF-1 and has been associated with higher levels of CYP2E1 transcription. It is conceivable that this CYP2E1 Rsa I polymorphism might contribute to differences in susceptibility to lung cancer. We conducted a case-control study of patients with incident lung cancer and population controls in Los Angeles County to examine the association between the CYP2E1 Rsa I polymorphism and lung cancer risk among African-Americans and Caucasians. Samples of white blood cell DNA sufficient for determination of the CYP2E1 Rsa I genotype by a polymerase chain reaction-based assay were obtained from 341 cases and 706 controls with data on lifetime smoking history. No subjects were homozygous for the CYP2E1 Rsa I rare c2 allele. The rare c2 allele was not associated with an increased risk of lung cancer (adjusted odds ratio, OR 0.72; 95% confidence interval, CI = 0.35-1.46). Among the population controls the percentage of subjects carrying the rare c2 allele was lower (p = 0.002) among African-Americans (2%) compared with Caucasians (8%). However, the association between the CYP2E1 Rsa I genotype and lung cancer risk did not differ between ethnic groups. There was no important association between the CYP2E1 Rsa I genotype and lung cancer risk in analyses stratified by cell-type, smoking history, gender, occupational asbestos exposure, and dietary intake of antioxidants vitamin C, vitamin E or beta carotene. Due to the low frequency of the c2 allele in these populations, larger studies would be necessary to rule out a modest association between the CYP2E1 Rsa I polymorphism and lung cancer risk.