Asthma and infectious respiratory disease in children--correlation to residence near hazardous waste sites

The association of preconception paternal metabolic syndrome on early childhood emergency department visits and hospitalizations

BACKGROUND

Increasing preconception paternal comorbidity has been associated with adverse pregnancy outcomes. However, whether the father's health impacts the child after birth is uncertain.

OBJECTIVES

In the present study, we examined the association of preconception paternal metabolic syndrome status with childhood emergency department visits and hospitalizations.

MATERIALS AND METHODS

This is a longitudinal cohort study of children (295,355 boys and 278,735 girls) born to linked pairs of fathers and mothers in the United States between 2009 and 2016 within the IBM MarketScan Research database. Associations between paternal and maternal metabolic syndrome component diagnoses and subsequent hospitalizations and emergency department visits for offspring within the first 2 years of life were determined.

RESULTS

Note that, 35.5% (203,617/574,090) of children had at least one emergency room visit and 6.1% (35,141/574,090) of children had an inpatient admission. After adjustment, the odds of inpatient admission and emergency department visits increased in a dose-dependent fashion among fathers with higher comorbidities. Similar trends were seen for emergency department visit utilization.

DISCUSSION AND CONCLUSION

Increasing paternal preconception comorbidity is associated with a higher risk that a child requires the emergency department and inpatient care in the first years of life. An opportunity exists to engage men in preconception counseling to optimize their and their offspring's health.

Population-level SDOH and Pediatric Asthma Health Care Utilization: A Systematic Review

CONTEXT

Spatial analysis is a population health methodology that can determine geographic distributions of asthma outcomes and examine their relationship to place-based social determinants of health (SDOH).

OBJECTIVES

To systematically review US-based studies analyzing associations between SDOH and asthma health care utilization by geographic entities.

DATA SOURCES

Pubmed, Medline, Web of Science, Scopus, and Cumulative Index to Nursing and Allied Health Literature.

STUDY SELECTION

Empirical, observational US-based studies were included if (1) outcomes included asthma-related emergency department visits or revisits, and hospitalizations or rehospitalizations; (2) exposures were ≥1 SDOH described by the Healthy People (HP) SDOH framework; (3) analysis occurred at the population-level using a geographic entity (eg, census-tract); (4) results were reported separately for children ≤18 years.

DATA EXTRACTION

Two reviewers collected data on study information, demographics, geographic entities, SDOH exposures, and asthma outcomes. We used the HP SDOH framework's 5 domains to organize and synthesize study findings.

RESULTS

The initial search identified 815 studies; 40 met inclusion criteria. Zip-code tabulation areas (n = 16) and census-tracts (n = 9) were frequently used geographic entities. Ten SDOH were evaluated across all HP domains. Most studies (n = 37) found significant associations between ≥1 SDOH and asthma health care utilization. Poverty and environmental conditions were the most often studied SDOH. Eight SDOH-poverty, higher education enrollment, health care access, primary care access, discrimination, environmental conditions, housing quality, and crime - had consistent significant associations with asthma health care utilization.

CONCLUSIONS

Population-level SDOH are associated with asthma health care utilization when evaluated by geographic entities. Future work using similar methodology may improve this research's quality and utility.

Along the energy justice continuum: An examination of energy disposal through the lens of feminist community based participatory action research

Energy justice research tends to focus on inequalities that result from energy systems, including from fossil fuel extraction to production, distribution, and consumption. However, little research has investigated local effects of the disposal of waste products from fossil fuel extraction. To better understand these impacts, we employed a case study approach with qualitative interviews of residents of Kettleman City, a rural community in California's Central Valley (USA) that hosts a hazardous waste landfill which accepts predominantly waste from fossil fuel production. Informed by a novel feminist community-based participatory action research approach (CBPAR), interview data were collected from residents in the Summer of 2019 and analyzed using deductive and inductive coding strategies. Resident interviews highlighted the disproportionate distribution of pollution and environmental degradation shouldered by the community along with their experiences of adverse health and social impacts. Our analysis revealed the importance of incorporating an intersectional perspective to frame resident experiences of energy injustice. Our research highlights the untapped potential of feminist-informed CBPAR to catalyze change and challenge the production of energy injustice from energy waste disposal.

A respiratory health survey of a subsurface smoldering landfill

In late 2010, a subsurface smoldering event was detected in the Bridgeton Sanitary Landfill in St. Louis County, Missouri. This was followed by complaints from nearby residents of foul odors emanating from the landfill. In 2016 a health survey was conducted of residents near the landfill and, as a comparison, other regions of St. Louis County. The survey was a two-stage cluster sample, where the first stage was census blocks, and the second stage was households within the census blocks. The health survey, which was conducted by face-to-face interviews of residents both near the landfill and away from the landfill, focused mainly on respiratory symptoms and diseases such as asthma and chronic obstructive pulmonary disease. The differences in the prevalence of asthma (26.7%, 95% CI 19.8-34.1 landfill vs 24.7%, 95% CI 15.7-33.6 comparison) and COPD (13.7%, 95% CI 7.2-20.3 landfill vs 12.5%, 95% CI 6.4-18.7 comparison) between the two groups were not statistically significant. Landfill households reported significantly more "other respiratory conditions," (17.6%, 95% CI 11.1-24.1 landfill vs 9.5%, 95% CI 4.8-14.3 comparison) and attacks of shortness of breath (33.9%, 95% CI 25.1-42.8 landfill vs 17.9%, 95% CI 12.3-23.5). Frequency of odor perceptions and level of worry about neighborhood environmental issues was higher among landfill households (p < 0.001). We conclude that the results do not support the hypothesis that people living near the Bridgeton Landfill have elevated respiratory or related illness compared to those people who live beyond the vicinity of the landfill.

Hazardous waste and health impact: a systematic review of the scientific literature

Waste is part of the agenda of the European Environment and Health Process and included among the topics of the Sixth Ministerial Conference on Environment and Health. Disposal and management of hazardous waste are worldwide challenges. We performed a systematic review to evaluate the evidence of the health impact of hazardous waste exposure, applying transparent and a priori defined methods. The following five steps, based on pre-defined systematic criteria, were applied. 1. Specify the research question, in terms of "Population-Exposure-Comparators-Outcomes" (PECO).

POPULATION

people living near hazardous waste sites; Exposure: exposure to hazardous waste; Comparators: all comparators; Outcomes: all diseases/health disorders. 2. Carry out the literature search, in Medline and EMBASE. 3. Select studies for inclusion: original epidemiological studies, published between 1999 and 2015, on populations residentially exposed to hazardous waste. 4. Assess the quality of selected studies, taking into account study design, exposure and outcome assessment, confounding control. 5. Rate the confidence in the body of evidence for each outcome taking into account the reliability of each study, the strength of the association and concordance of results.Fifty-seven papers of epidemiological investigations on the health status of populations living near hazardous waste sites were selected for the evidence evaluation. The association between 95 health outcomes (diseases and disorders) and residential exposure to hazardous waste sites was evaluated. Health effects of residential hazardous waste exposure, previously partially unrecognized, were highlighted. Sufficient evidence was found of association between exposure to oil industry waste that releases high concentrations of hydrogen sulphide and acute symptoms. The evidence of causal relationship with hazardous waste was defined as limited for: liver, bladder, breast and testis cancers, non-Hodgkin lymphoma, asthma, congenital anomalies overall and anomalies of the neural tube, urogenital, connective and musculoskeletal systems, low birth weight and pre-term birth; evidence was defined as inadequate for the other health outcomes. The results, although not conclusive, provide indications that more effective public health policies on hazardous waste management are urgently needed. International, national and local authorities should oppose and eliminate poor, outdated and illegal practices of waste disposal, including illegal transboundary trade, and increase support regulation and its enforcement.

Binding of Pollutants to Biomolecules: A Simulation Study

A number of cases around the world have been reported where animals were found dead or dying with symptoms resembling a thiamine (vitamin B) deficiency, and for some of these, a link to pollutants has been suggested. Here, we investigate whether biomolecules involved in thiamin binding and transport could be blocked by a range of different pollutants. We used in silico docking of five compound classes (25 compounds in total) to each of five targets (prion protein, ECF-type ABC transporter, thi-box riboswitch receptor, thiamin pyrophosphokinase, and YKoF protein) and subsequently performed molecular dynamics (MD) simulations to assess the stability of the complexes. The compound classes were thiamin analogues (control), pesticides, veterinary medicines, polychlorinated biphenyls, and dioxins, all of which are prevalent in the environment to some extent. A few anthropogenic compounds were found to bind the ECF-type ABC transporter, but none binds stably to prion protein. For the riboswitch, most compounds remained in their binding pockets during 50 ns of MD simulation, indicating that RNA provides a promiscuous binding site. In both YKoF and thiamin pyrophosphokinase (TPK), most compounds remain tightly bound. However, TPK biomolecules undergo pollutant-induced conformational changes. Although most compounds are found to bind to some of these targets, a larger data set is needed along with more quantitative methods like free energy perturbation calculations before firm conclusions can be drawn. This study is in part a test bed for large-scale quantitative computational screening of interactions between biological entities and pollutant molecules.

The importance of toxicity in determining the impact of hazardous air pollutants on the respiratory health of children in Tennessee

Respiratory diseases, exacerbated through point source pollution, are currently among the leading causes of hospitalization of children in the United States. This paper investigates the relationship between the proximity of hazardous air pollutants (HAPs) emitted from Toxic Release Inventory (TRI) facilities and the number of children diagnosed in hospitals with a respiratory disease in Tennessee. The importance of controlling for toxicity of those HAPs is of particular interest. Hospital discharge, socioeconomic, TRI emission, and HAP toxicity data are used to estimate, via Generalized Linear Methods, a logistic regression model describing the relationship between the percent of children living in a zip code area treated for respiratory illness and the average annual emissions over the previous 10 years of HAPs from TRI sites in that area. Controlling for area socioeconomic characteristics, we find that accounting for toxicity is important in uncovering the relationship between HAP emissions and respiratory health of children. A one standard deviation increase in toxicity-weighted emissions per 100 square miles is associated with an increase in the number of children diagnosed with asthma (chronic bronchitis) by about 1205 (260). The evidence suggests that, with a goal to improving children's respiratory health, monitoring the toxicity of chemicals being emitted is at least as important as simply monitoring total emission levels. This suggests that the EPA should consider making efforts toward establishing toxicity adjusted emission guidelines.

Internal exposure levels of typical POPs and their associations with childhood asthma in Shanghai, China

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) are common persistent organic pollutants (POPs) that may be associated with childhood asthma. The concentrations of PBDEs, PCBs and OCPs were analyzed in pooled serum samples from both asthmatic and non-asthmatic children. The differences in the internal exposure levels between the case and control groups were tested (p value <0.0012). The associations between the internal exposure concentrations of the POPs and childhood asthma were estimated based on the odds ratios (ORs) calculated using logistic regression models. There were significant differences in three PBDEs, 26 PCBs and seven OCPs between the two groups, with significantly higher levels in the cases. The multiple logistic regression models demonstrated that the internal exposure concentrations of a number of the POPs (23 PCBs, p,p'-DDE and α-HCH) were positively associated with childhood asthma. Some synergistic effects were observed when the children were co-exposed to the chemicals. BDE-209 was positively associated with asthma aggravation. This study indicates the potential relationships between the internal exposure concentrations of particular POPs and the development of childhood asthma.

Integrating environmental and human health databases in the great lakes basin: themes, challenges and future directions

Many government, academic and research institutions collect environmental data that are relevant to understanding the relationship between environmental exposures and human health. Integrating these data with health outcome data presents new challenges that are important to consider to improve our effective use of environmental health information. Our objective was to identify the common themes related to the integration of environmental and health data, and suggest ways to address the challenges and make progress toward more effective use of data already collected, to further our understanding of environmental health associations in the Great Lakes region. Environmental and human health databases were identified and reviewed using literature searches and a series of one-on-one and group expert consultations. Databases identified were predominantly environmental stressors databases, with fewer found for health outcomes and human exposure. Nine themes or factors that impact integration were identified: data availability, accessibility, harmonization, stakeholder collaboration, policy and strategic alignment, resource adequacy, environmental health indicators, and data exchange networks. The use and cost effectiveness of data currently collected could be improved by strategic changes to data collection and access systems to provide better opportunities to identify and study environmental exposures that may impact human health.

Association between hospital discharge rate for female breast cancer and residence in a zip code containing hazardous waste sites

BACKGROUND

Exposure to chemicals plays a role in risk of breast cancer. However, possible associations between risk of breast cancer and residential proximity to hazardous waste sites (HWSs) have not been reported.

METHODS

We determined rates of hospital discharge with a diagnosis of female breast cancer in relation to residence in a zip code containing HWSs in New York State (NYS) after adjustment for ethnicity, age, income and urbanicity. Waste exposure was assessed by both the number of waste sites and the type of contaminants. Negative binomial regression was used to test the associations.

RESULTS

After controlling for confounders, the hospital discharge rate of breast cancer for women living in zip codes having four or more HWSs or in zip codes having one HWS increased significantly (at the 0.05 level) by 9.1% and 6.4%, as compared to those living in a zip code with no HWS. The association for women living in zip codes having two or three HWSs was not significant. This indicates that the extent of exposure cannot be assessed solely by the number of waste sites. The discharge rate for women living in zip codes containing at least one volatile organic compound (VOC) waste site was significantly increased 5.6% as compared to those living in a zip code without any HWS, while the increases were not significant for women living in zip codes containing waste sites with persistent organic pollutants (POPs) or other contaminants. The significant associations were stronger for African American than Caucasian women and stronger in more urbanized than in rural areas.

CONCLUSIONS

Residence within a geographic area (defined by zip codes) that includes a hazardous waste site with VOCs is significantly associated with an increased rate of hospitalization for breast cancer, and the association is stronger for African American than Caucasian women and stronger in more urbanized than in rural areas after adjustment for the confounders.

Health effects associated with the disposal of solid waste in landfills and incinerators in populations living in surrounding areas: a systematic review

OBJECTIVES

Potential health hazards for the environment and people living nearby landfills and incinerators are claimed to be related to several methods of waste management. Independent systematic review of the scientific literature is a key procedure to support the lay public and policy makers to achieve informed decisions.

METHODS

The study design and potential biases of papers retrieved in this comprehensive literature search were analyzed.

RESULTS

The most consistent result is that the risks of congenital anomalies and hospitalization due to respiratory disease are likely to be real nearby special waste landfills. From the very little information on exclusively urban waste depots it is reasonable to say that correct management of landfill does not increase the risk of these health effects. It is confirmed that historically incinerators are an important source of pollution and harm for the health of populations living nearby; however, changes in technology are producing more reassuring results.

CONCLUSIONS

A moderate level of confidence is possible in limited areas of knowledge, implying the need to overcome the limitations of current studies about exposure assessment and to control confounders at the individual level.

Intakes of long-chain omega-3 (n-3) PUFAs and fish in relation to incidence of asthma among American young adults: the CARDIA study

BACKGROUND

Although long-chain ω-3 (n-3) PUFAs (LCω3PUFAs) have been linked to the prevention of some inflammatory disorders, little is known about the association between these fatty acids and incidence of asthma.

OBJECTIVE

The objective was to prospectively investigate the association between LCω3PUFAs and fish intake and incidence of asthma among American young adults.

DESIGN

A 20-y follow-up longitudinal analysis was conducted in a biracial cohort of 4162 Americans, aged 18-30 y, with a history of asthma at baseline in 1985. Diet was assessed by a validated interviewer-administered quantitative food-frequency questionnaire at the examinations in 1985, 1992, and 2005. Incident self-reported asthma was defined as having a physician diagnosis of asthma and/or the use of asthma medications between 1985 and 2005.

RESULTS

During the 20-y follow-up, 446 incident cases of asthma were identified. LCω3PUFA intake was significantly inversely associated with incidence of asthma after adjustment for sociodemographic, major lifestyle, and dietary confounders. The multivariable-adjusted HR for the highest quintile of LCω3PUFA intake as compared with the lowest quintile was 0.46 (95% CI: 0.33, 0.64; P-trend < 0.01). However, a higher frequency of nonfried fish consumption was not significantly associated with the risk of asthma. DHA showed a greater inverse association than did EPA. The association between LCω3PUFAs and incident asthma was not appreciably modified by sex, race, BMI, smoking status, or atopic status.

CONCLUSION

This study showed that intakes of LCω3PUFAs are inversely longitudinally associated with the incidence of asthma in American young adults.

Association between residential proximity to fuel-fired power plants and hospitalization rate for respiratory diseases

BACKGROUND

Air pollution is known to cause respiratory disease. Unlike motor vehicle sources, fuel-fired power plants are stationary.

OBJECTIVE

Using hospitalization data, we examined whether living near a fuel-fired power plant increases the likelihood of hospitalization for respiratory disease.

METHODS

Rates of hospitalization for asthma, acute respiratory infection (ARI), and chronic obstructive pulmonary disease (COPD) were estimated using hospitalization data for 1993-2008 from New York State in relation to data for residences near fuel-fired power plants. We also explored data for residential proximity to hazardous waste sites.

RESULTS

After adjusting for age, sex, race, median household income, and rural/urban residence, there were significant 11%, 15%, and 17% increases in estimated rates of hospitalization for asthma, ARI, and COPD, respectively, among individuals > 10 years of age living in a ZIP code containing a fuel-fired power plant compared with one that had no power plant. Living in a ZIP code with a fuel-fired power plant was not significantly associated with hospitalization for asthma or ARI among children < 10 years of age. Living in a ZIP code with a hazardous waste site was associated with hospitalization for all outcomes in both age groups, and joint effect estimates were approximately additive for living in a ZIP code that contained a fuel-fired power plant and a hazardous waste site.

CONCLUSIONS

Our results are consistent with the hypothesis that exposure to air pollution from fuel-fired power plants and volatile compounds coming from hazardous waste sites increases the risk of hospitalization for respiratory diseases.

Review Article: Persistent organic pollutants and landfills - a review of past experiences and future challenges

The landfilling and dumping of persistent organic pollutants (POPs) and other persistent hazardous compounds, such as polychlorinated biphenyls (PCBs), hexachlorocyclohaxane (HCH), polybrominated diphenylether (PBDEs) or perfluorooctane sulfonic acid (PFOS) can have significant adverse environmental consequences. This paper reviews past experiences with such disposal practices and highlights their unsustainability due to the risks of contamination of ecosystems, the food chain, together with ground and drinking water supplies. The use and associated disposal of POPs have been occurring for over 50 years. Concurrent with the phase-out of some of the most hazardous chemicals, the production of new POPs, such as brominated and fluorinated compounds has increased since the 1990s. These latter compounds are commonly used in a wide range of consumer goods, and as consumer products reach the end of their useful lives, ultimately enter waste recycling and disposal systems, in particular at municipal landfills. Because of their very slow, or lack of degradability, POPs will persist in landfills for many decades and possibly centuries. Over these extended time periods engineered landfill systems and their liners are likely to degrade, thus posing a contemporary and future risk of releasing large contaminant loads to the environment. This review highlights the necessity for alternative disposal methods for POP wastes, including destruction or complete removal from potential environmental release. In addition to such end of pipe solutions a policy change in the use pattern of persistent toxic chemicals is inevitable. In addition, inventories for the location and quantity of POPs in landfills, together with an assessment of their threat to ecosystems, drinking water and food resources are identified as key measures to facilitate appropriate management of risks. Finally the challenges of POP wastes in transition/developing countries, the risk of increased leaching of POPs from landfills due to climate change, and the possible negative impact of natural attenuation processes are considered.

Review Series: What goes around, comes around: childhood influences on later lung health?: Relationship between environmental exposures in children and adult lung disease: The case for outdoor exposures

There is a growing understanding that chronic respiratory diseases in adults have their origins in early life. Adverse environmental exposures occurring in vulnerable periods during lung growth and development in the fetal period and in early childhood that alter lung structure and limit the growth in lung function may have lifelong consequences. Evidence is increasing that exposure to the ambient environment, including air pollutants, persistent toxic substances, water pollutants and respiratory viral infections, can inhibit lung function growth and predispose to chronic non-malignant lung diseases. These exposures generally interact with a genetic predisposition, and gene—environment interactions and epigenetic phenomena are attracting considerable study. An understanding of how ambient exposures impact on normal lung growth and development will aid in understanding of how chronic respiratory diseases of adults develop and may lead to new preventative strategies.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 November 2007 and 31 October 2008 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.

Environmental causes of violence

Violent and anti-social behavior is usually attributed to social factors, including poverty, poor education, and family instability. There is also evidence that many forms of violent behavior are more frequent in individuals of lower IQ. The role of exposure to environmental contaminants has received little attention as a factor predisposing to violent behavior. However a number of environmental exposures are documented to result in a common pattern of neurobehavioral effects, including lowered IQ, shortened attention span, and increased frequency of antisocial behavior. This pattern is best described for children exposed to lead early in life, but a similar pattern is seen upon exposure to polychlorinated biphenyls and methyl mercury. Although not as extensively studied, similar decrements in IQ are seen upon exposure to arsenic and secondhand smoke (SHS) exposure. Prenatal and postnatal SHS exposure is also associated with increased rates of conduct disorder and attention deficit hyperactivity. Recent evidence suggests that temporal trends in rates of violent crime in many nations are consistent with earlier preschool blood lead trends, with a lag of about 20 years. These ecologic correlations are consistent with many controlled studies suggesting that lead-exposed children suffer irreversible brain alterations that make them more likely to commit violent crimes as young adults. If this pattern is true for lead and other contaminants, the most effective way to fight crime may be to prevent exposure to these contaminants.

Increased prevalence of risk factors for morbidity and mortality in the US Hispanic CF population

Hispanic ethnicity is an independent risk factor for increased morbidity and mortality in cystic fibrosis (CF) patients. In order to compare the prevalence of risk factors for morbidity and mortality between the Hispanic CF population and the non-Hispanic CF population, we performed a cross-sectional study of patients in the 2004 Cystic Fibrosis Foundation Patient Registry. Among 22,714 CF patients, 1,511 were identified as ethnic Hispanic. Hispanic patients were diagnosed earlier (2.8 vs. 3.3 years, P = 0.005) and acquired Pseudomonas aeruginosa at a younger age (6.6 years vs. 10 years, P < 0.001). FEV(1) was lower for Hispanic patients (81.5% vs. 87% predicted for those under 18 years old [P < 0.001] and 2.1 L vs. 2.3 L for those 18 years and older [P = 0.01]). Hispanic patients had similar or better nutritional status. Hispanic patients were more likely to be diagnosed with liver disease (OR 1.31 [1.1, 1.56]) but less likely to be diagnosed with depression (OR 0.53 [0.39, 0.68]), bone and joint disease (OR 0.55 [0.41, 0.71]), or CF-related diabetes (OR 0.53 [0.43, 0.62]). Hispanic patients had lower median income by zip code ($41,930 vs. $47,341; P < 0.001), a higher rate of government insurance (55.2% vs. 32.0%; P < 0.001), and greater percentage of mothers with less than a high school education (26.7% vs. 6.5%; P < 0.001). We conclude that there is an increased prevalence of important risk factors for morbidity and mortality in the Hispanic CF population.

Asthma and infectious respiratory disease in relation to residence near hazardous waste sites

The hypothesis that simply living near a hazardous waste site increases risk of exposure to chemicals was tested. Using data from the New York Statewide Planning and Research Cooperative System, which provides information on hospitalized patients, plus information on the location and contents of every known hazardous waste site in New York, the rates of hospitalization for asthma (ICD-9 493), infectious respiratory disease (ICD-9 460-466, 480-487, and 490-491), and Chronic obstructive pulmonary disease (COPD) (ICD-9 490-492 and 494-496) were determined among individuals who lived in (a) zip codes containing or abutting a hazardous waste site with persistent organic pollutants (POPs), (b) zip codes containing or abutting a hazardous waste site, but not one with POPs, and (c) zip codes that do not contain or abut an identified hazardous waste site. After adjustment for MHI, race, gender and urban or rural residence, there was a significantly elevated risk of asthma (rate ratio (RR) = 1.09), infectious respiratory disease (RR = 1.15), and COPD (RR = 1.19) in individuals living in a zip code with a POP waste site, and a significantly elevated risk of asthma (RR = 1.09), infectious respiratory disease (RR = 1.12), and COPD (RR = 1.13) associated with residence in a zip code containing a waste site, but not one with POPs, both relative to residence in a zip code without a waste site. These observations are consistent with the hypothesis that simply living near a hazardous waste site increases risk of exposure to substances that contribute to respiratory disease.