The environmental burden of disease in Canada: respiratory disease, cardiovascular disease, cancer, and congenital affliction

Critical Time Windows for Air Pollution Exposure and Birth Weight in a Multicity Canadian Pregnancy Cohort

BACKGROUND

Maternal prenatal exposure to air pollution has been associated with adverse birth outcomes. However, previous studies focused on a priori time intervals such as trimesters reported inconsistent associations.

OBJECTIVES

We investigated time-varying vulnerability of birth weight to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) using flexible time intervals.

METHODS

We analyzed 1,300 live, full-term births from Maternal-Infant Research on Environmental Chemicals, a Canadian prospective pregnancy cohort spanning 10 cities (2008-2011). Daily PM2.5 and NO2 concentrations were estimated from ground-level monitoring, satellite models, and land-use regression, and assigned to participants from pre-pregnancy through delivery. We developed a flexible two-stage modeling method-using a Bayesian Metropolis-Hastings algorithm and empirical density threshold-to identify time-dependent vulnerability to air pollution without specifying exposure periods a priori. This approach identified critical windows with varying lengths (2-363 days) and critical windows that fell within, or straddled, predetermined time periods (i.e., trimesters). We adjusted the models for detailed infant and maternal covariates.

RESULTS

Critical windows associated with reduced birth weight were identified during mid- to late-pregnancy for both PM2.5 and NO2: -6 g (95% credible interval: -11, -1 g) and -5 g (-10, -0.1 g) per µg/m3 PM2.5 during gestational days 91-139 and 249-272, respectively; and -3 g (-5, -1 g) per ppb NO2 during days 55-145.

DISCUSSION

We used a novel, flexible selection method to identify critical windows when maternal exposures to air pollution were associated with decrements in birth weight. Our results suggest that air pollution impacts on fetal development may not be adequately captured by trimester-based analyses.

An approach to estimating the environmental burden of cancer from known and probable carcinogens: application to Ontario, Canada

BACKGROUND

Quantifying the potential cancer cases associated with environmental carcinogen exposure can help inform efforts to improve population health. This study developed an approach to estimate the environmental burden of cancer and applied it to Ontario, Canada. The purpose was to identify environmental carcinogens with the greatest impact on cancer burden to support evidence-based decision making.

METHODS

We conducted a probabilistic assessment of the environmental burden of cancer in Ontario. We selected 23 carcinogens that we defined as "environmental" (e.g., pollutants) and were relevant to the province, based on select classifications provided by the International Agency for Research on Cancer. We evaluated population exposure to the carcinogens through inhalation of indoor/outdoor air; ingestion of food, water, and dust; and exposure to radiation. We obtained or calculated concentration-response functions relating carcinogen exposure and the risk of developing cancer. Using both human health risk assessment and population attributable fraction models in a Monte Carlo simulation, we estimated the annual cancer cases associated with each environmental carcinogen, reporting the simulation summary (e.g., mean and percentiles).

RESULTS

We estimated between 3540 and 6510 annual cancer cases attributable to exposure to 23 environmental carcinogens in Ontario. Three carcinogens were responsible for over 90% of the environmental burden of cancer: solar ultraviolet (UV) radiation, radon in homes, and fine particulate matter (PM_2.5) in outdoor air. Eight other carcinogens had an estimated mean burden of at least 10 annual cancer cases: acrylamide, arsenic, asbestos, chromium, diesel engine exhaust particulate matter, dioxins, formaldehyde, and second-hand smoke. The remaining 12 carcinogens had an estimated mean burden of less than 10 annual cancer cases in Ontario.

CONCLUSIONS

We found the environmental burden of cancer in Ontario to fall between previously estimated burdens of alcohol and tobacco use. These results allow for a comparative assessment across carcinogens and offer insights into strategies to reduce the environmental burden of cancer. Our analysis could be adopted by other jurisdictions and repeated in the future for Ontario to track progress in reducing cancer burden, assess newly classified environmental carcinogens, and identify top burden contributors.

Characterization of maternal plasma biomarkers associated with delivery of small and large for gestational age infants in the MIREC study cohort

Objective

Neonatal morbidity and mortality can be influenced by maternal health status. Information on maternal and fetal biomarkers of adverse health outcomes is limited. This work aims at identifying maternal biomarkers associated with low and high birth weight for gestational age groups.

Design and settings

Population-based prospective cohort study of the potential adverse health effects of exposure to environmental contaminants on pregnancy and infant health.

Methods

Third trimester maternal plasma samples (n = 1588) from a pregnancy cohort (Maternal-Infant Research on Environmental Chemicals Study, MIREC) were analyzed for changes in a target spectrum of biomarkers of vascular health (e.g., matrix metalloproteinases MMPs, vascular endothelial cell growth factor VEGF), inflammation (e.g. cellular adhesion molecules CAMs, cytokines, chemokines) by affinity-based multiplex protein array analyses. Multivariate logistic regression analyses were done to examine associations between target plasma biomarkers, maternal-infant characteristics, and birth weight outcomes assessed as small for gestational age (SGA) ≤10^th percentile and large for gestational age (LGA) ≥90^th percentile groups.

Results and outcomes

Our results revealed that maternal plasma biomarkers monocyte chemoattractant protein-1 MCP-1 (p<0.05, +ve) and VEGF (p<0.05, -ve) along with parity = 1 (p<0.01, -ve) and gestational hypertension (p<0.05, +ve) were associated with SGA births. Meanwhile, LGA was associated with maternal plasma VEGF (p<0.05, +ve) and MMP-9 (p<0.05, -ve) and gestational hypertension (p<0.01, +ve), pre-pregnancy body mass index (p<0.01, +ve), parity (p<0.05, +ve) and education (p<0.05, -ve).

Conclusions

Third trimester maternal plasma biomarkers in combination with maternal health and socioeconomic characteristics can be useful in predicting SGA and LGA outcomes. Maternal vascular health and inflammatory status may contribute to both SGA and LGA births through distinct molecular mechanisms.

National and sub-national age-sex specific and cause-specific mortality and disability-adjusted life years (DALYs) attributable to household air pollution from solid cookfuel use (HAP) in Iran, 1990-2013

National and sub-national mortality, years of life lost due to premature mortality (YLLs), years lived with disability (YLDs) and disability-adjusted life years (DALYs) for household air pollution from solid cookfuel use (HAP) in Iran, 1990-2013 were estimated based on the Global Burden of Disease Study 2013 (GBD 2013). The burden of disease attributable to HAP was quantified by the comparative risk assessment method using four inputs: (1) exposure to HAP, (2) the theoretical minimum risk exposure level (TMREL), (3) exposure-response relationships of related causes (4) disease burden of related causes. All across the country, solid fuel use decreased from 5.26% in 1990 to 0.15% in 2013. The drastic reduction of solid fuel use leaded to DALYs attributable to HAP fell by 97.8% (95% uncertainty interval 97.7-98.0%) from 87,433 (51072-144303) in 1990 to 1889 (1016-3247) in 2013. Proportion of YLLs in DALYs from HAP decreased from 95.7% in 1990 to 86.6% in 2013. Contribution of causes in the attributable DALYs was variable during the study period and in 2013 was in the following order: ischemic heart disease for 43.4%, chronic obstructive pulmonary disease for 24.7%, hemorrhagic stroke for 9.7%, lower respiratory infections for 9.3%, ischemic stroke for 7.8%, lung cancer for 3.4% and cataract for 1.8%. Based on the Gini coefficient, the spatial inequality of the disease burden from HAP increased during the study period. The remained burden of disease was relatively scarce and it mainly occurred in seven southern provinces. Further reduction of the disease burden from HAP as well as compensation of the increasing spatial inequality in Iran could be attained through an especial plan for providing cleaner fuels in the southern provinces.

Respiratory Diseases in University Students Associated with Exposure to Residential Dampness or Mold

University students are frequently exposed to residential dampness or mold (i.e., visible mold, mold odor, dampness, or water leaks), a well-known contributor to asthma, allergic rhinitis, and respiratory infections. This study aims to: (a) describe the prevalence of these respiratory diseases among university students; and (b) examine the independent contribution of residential dampness or mold to these diseases. An online survey was conducted in March 2014 among the 26,676 students registered at the Université de Sherbrooke (Quebec, Canada). Validated questions and scores were used to assess self-reported respiratory diseases (i.e., asthma-like symptoms, allergic rhinitis, and respiratory infections), residential dampness or mold, and covariates (e.g., student characteristics). Using logistic regressions, the crude and adjusted odd ratios between residential dampness or mold and self-reported respiratory diseases were examined. Results from the participating students (n = 2097; response rate: 8.1%) showed high prevalence of allergic rhinitis (32.6%; 95% CI: 30.6–34.7), asthma-like symptoms (24.0%; 95% CI: 22.1–25.8) and respiratory infections (19.4%; 95% CI: 17.7–21.2). After adjustment, exposure to residential dampness or mold was associated with allergic rhinitis (OR: 1.25; 95% CI: 1.01–1.55) and asthma-like symptoms (OR: 1.70; 95% CI: 1.37–2.11), but not with respiratory infections (OR: 1.07; 95% CI: 0.85–1.36). Among symptomatic students, this exposure was also associated with uncontrolled and burdensome respiratory symptoms (p < 0.01). University students report a high prevalence of allergic rhinitis, asthma-like symptoms and respiratory infections. A common indoor hazard, residential dampness or mold, may play a role in increasing atopic respiratory diseases and their suboptimal control in young adults. These results emphasize the importance for public health organizations to tackle poor housing conditions, especially amongst university students who should be considered “at-risk”.

Human exposure to environmental contaminants and congenital anomalies: a critical review

Congenital anomalies are an important cause of infant mortality and disability. Developmental exposure to environmental contaminants is thought to increase the risk for congenital anomalies. Herein, we describe a critical review of the literature conducted between February and March 2014 yielding 3057 references from which 97 unique relevant articles published from 2003 through 2014 were evaluated. Common congenital anomalies including hypospadias, cryptorchidism, anogenital distance (AGD), congenital heart defects and oral clefts were well represented in the literature whereas other outcomes such as neural tube defects, limb deficiency defects and gastroschisis were rarely described. While definitions used for congenital anomalies and methods of ascertainment were usually consistent across studies, inconsistencies were frequently found in grouping of different congenital heart defects. Despite strong links between some congenital anomalies and parental occupation, these studies are unable to provide clear insight into the specific chemicals responsible owing to lack of direct measures of exposure. In comparison, data are mixed for contaminant exposures at concentrations representative of results from contemporary biomonitoring studies. Of the environmental contaminants studied, the association between phthalate exposures and developmental abnormalities of the male reproductive tract received the greatest attention. Important limitations of the literature studied relate to adequacy of sample size, absence of or weaknesses in exposure assessment methodologies, failure to account for biological plausibility and grouping of congenital anomalies with divergent mechanisms. We conclude that the literature is inadequate at this time to support a conclusion that exposure to environmental contaminants are or are not associated with increased risks for congenital anomalies in the general population.

The right to a healthy environment: A prescription for Canada

This invited commentary summarizes the need for stronger Canadian environmental laws and policies. The environmental burden of disease in Canada is substantial. In part this is due to environmental laws and policies that are significantly weaker and less effective than corresponding rules in other wealthy industrialized nations. One promising approach is recognition of the right to live in a healthy environment. In particular, constitutional recognition of this right in 100 nations has led to stronger environmental laws, better enforcement of those laws, enhanced public participation in environmental decision-making, and superior environmental outcomes (e.g., faster progress in reducing air pollution and greenhouse gas emissions). In light of Canada's weak environmental record, this potentially transformative approach is particularly promising.

Environmental Asthma Reduction Potential Estimates for Selected Mitigation Actions in Finland Using a Life Table Approach

Aims: To quantify the reduction potential of asthma in Finland achievable by adjusting exposures to selected environmental factors. Methods: A life table model for the Finnish population for 1986–2040 was developed and Years Lived with Disability caused by asthma and attributable to the following selected exposures were estimated: tobacco smoke (smoking and second hand tobacco smoke), ambient fine particles, indoor dampness and mould, and pets. Results: At baseline (2011) about 25% of the total asthma burden was attributable to the selected exposures. Banning tobacco was the most efficient mitigation action, leading to 6% reduction of the asthma burden. A 50% reduction in exposure to dampness and mould as well as a doubling in exposure to pets lead each to a 2% reduction. Ban of urban small scale wood combustion, chosen as a mitigation action to reduce exposure to fine particles, leads to a reduction of less than 1% of the total asthma burden. Combination of the most efficient mitigation actions reduces the total asthma burden by 10%. A more feasible combination of mitigation actions leads to 6% reduction of the asthma burden. Conclusions: The adjustment of environmental exposures can reduce the asthma burden in Finland by up to 10%.

Environmental equity research: review with focus on outdoor air pollution research methods and analytic tools

The objective of this study was to review environmental equity research on outdoor air pollution and, specifically, methods and tools used in research, published in English, with the aim of recommending the best methods and analytic tools. English language publications from 2000 to 2012 were identified in Google Scholar, Ovid MEDLINE, and PubMed. Research methodologies and results were reviewed and potential deficiencies and knowledge gaps identified. The publications show that exposure to outdoor air pollution differs by social factors, but findings are inconsistent in Canada. In terms of study designs, most were small and ecological and therefore prone to the ecological fallacy. Newer tools such as geographic information systems, modeling, and biomarkers offer improved precision in exposure measurement. Higher-quality research using large, individual-based samples and more precise analytic tools are needed to provide better evidence for policy-making to reduce environmental inequities.

The shared pathoetiological effects of particulate air pollution and the social environment on fetal-placental development

Exposure to particulate air pollution and socioeconomic risk factors are shown to be independently associated with adverse pregnancy outcomes; however, their confounding relationship is an epidemiological challenge that requires understanding of their shared etiologic pathways affecting fetal-placental development. The purpose of this paper is to explore the etiological mechanisms associated with exposure to particulate air pollution in contributing to adverse pregnancy outcomes and how these mechanisms intersect with those related to socioeconomic status. Here we review the role of oxidative stress, inflammation and endocrine modification in the pathoetiology of deficient deep placentation and detail how the physical and social environments can act alone and collectively to mediate the established pathology linked to a spectrum of adverse pregnancy outcomes. We review the experimental and epidemiological literature showing that diet/nutrition, smoking, and psychosocial stress share similar pathways with that of particulate air pollution exposure to potentially exasperate the negative effects of either insult alone. Therefore, socially patterned risk factors often treated as nuisance parameters should be explored as potential effect modifiers that may operate at multiple levels of social geography. The degree to which deleterious exposures can be ameliorated or exacerbated via community-level social and environmental characteristics needs further exploration.

Reducing cardiovascular health impacts from traffic-related noise and air pollution: intervention strategies

Recent studies suggest that exposure to both traffic-related air pollution (TrAP) and to road traffic noise (RTN) are independent risk factors for cardiovascular disease (CVD). While the exact pathophysiologic mechanisms are not known, plausible biological models exist for both associations. This paper describes interventions and mitigating measures aimed at reducing both air and noise pollution emitted from traffic. Nine types of interventions are examined within the four strategic themes of (i) land-use planning and transportation management, (ii) reduction of vehicle emissions, (iii) modification of existing structures, and (iv) behavioral change. Not all interventions result in concomitant reductions of air and noise pollutant exposures. Most interventions that rely on a scientific basis to reduce CVD are directed at reducing TrAP. Interventions identified with the greatest potential benefits focus on the pollutant source, such as reductions in traffic volume and air pollutant emissions, and are more easily realized, and likely cheaper, if they are considered in the land-use planning stages with less reliance on behavioral changes.

Quality of cardiovascular disease care in Ontario, Canada: missed opportunities for prevention - a cross sectional study

Background

Primary care plays a key role in the prevention and management of cardiovascular disease (CVD). We examined primary care practice adherence to recommended care guidelines associated with the prevention and management of CVD for high risk patients.

Methods

We conducted a secondary analysis of cross-sectional baseline data collected from 84 primary care practices participating in a large quality improvement initiative in Eastern Ontario from 2008 to 2010. We collected medical chart data from 4,931 patients who either had, or were at high risk of developing CVD to study adherence rates to recommended guidelines for CVD care and to examine the proportion of patients at target for clinical markers such as blood pressure, lipid levels and hemoglobin A1c.

Results

Adherence to preventive care recommendations was poor. Less than 10% of high risk patients received a waistline measurement, half of the smokers received cessation advice, and 7.7% were referred to a smoking cessation program. Gaps in care exist for diabetes and kidney disease as 54.9% of patients with diabetes received recommended hemoglobin-A1c screenings, and only 55.8% received an albumin excretion test. Adherence rates to recommended guidelines for coronary artery disease, hypertension, and dyslipidemia were high (>75%); however <50% of patients were at target for blood pressure or LDL-cholesterol levels (37.1% and 49.7% respectively), and only 59.3% of patients with diabetes were at target for hemoglobin-A1c.

Conclusions

There remain significant opportunities for primary care providers to engage high risk patients in prevention activities such as weight management and smoking cessation. Despite high adherence rates for hypertension, dyslipidemia, and coronary artery disease, a significant proportion of patients failed to meet treatment targets, highlighting the complexity of caring for people with multiple chronic conditions.

Trial Registration

NCT00574808

Increase in metabolic syndrome-related hospitalizations in relation to environmental sources of persistent organic pollutants

Evidence from cell studies indicates that persistent organic pollutants (POP) can induce insulin resistance, an essential component of the metabolic syndrome (MetS). We hypothesized that residential proximity to environmental sources of POP would be associated with the MetS in the population. The present study examined the association between residency in a zip code containing or abutting environmental sources of POP and MetS-related hospitalization rates. Hospitalization data were obtained from the New York Statewide Planning and Research Cooperative System. Relative risks (RR) were calculated as hospitalization rate ratios. Adjusted RR and their 95% confidence intervals (CI) were estimated by multivariable Poisson regression. A higher proportion of African Americans resided in POP zip codes compared to Caucasians (25.9% and 24.3%, respectively, p < 0.01). Residence in POP zip codes was associated with a statistically significant 39.2% increase in MetS-related hospitalization rates, adjusted for race, gender, and age (adjusted RR = 1.392, 95% CI: 1.032-1.879, p = 0.030). Increase in age was independently associated with higher MetS-related hospitalization rates (p for trend < 0.001). Our findings contribute to the body of evidence supporting the hypothesis of POP constituting an environmental risk factor for the MetS. Further studies investigating exposure to POP and insulin resistance are warranted.

Residential proximity to environmental sources of persistent organic pollutants and first-time hospitalizations for myocardial infarction with comorbid diabetes mellitus: a 12-year population-based study

OBJECTIVES

Environmental exposure to persistent organic pollutants (POPs) has been associated with an increased risk of both acute myocardial infarction (AMI) and diabetes mellitus (DM). A study of first-time hospitalizations for AMI with DM as a comorbidity in populations presumed to be exposed or not exposed on the basis of residence near POPs sites was conducted to investigate whether exposure to POPs increases the environmental burden of disease.

MATERIALS AND METHODS

We examined the association between residential proximity to environmental sources of POPs and hospitalization rates for first-time AMI with comorbid DM in 31,428 patients aged 25-74 years, using the New York Statewide Planning and Research Cooperative System data for a 12-year period (1993-2004). Environmental exposure status was assessed based on the zip code of residence. Adjusted relative risks (RR) of AMI hospitalization were estimated by multivariate Poisson regression.

RESULTS

Hospitalization rates for first-time AMI with comorbid DM were significantly greater in populations living near POPs sites (adjusted RR = 1.169, 95% CI: 1.014-1.347, p < 0.05). These rates were also significantly higher in African Americans than in Caucasians (adjusted RR = 1.902, 95% CI: 1.659-2.180, p < 0.001), in males (adjusted RR = 1.767, 95% CI: 1.695-1.843, p < 0.001), and for older ages (p for trend < 0.001). These findings, consistent with established non-modifiable risk factors, support the plausibility of our model.

CONCLUSIONS

Residential proximity to environmental sources of POPs is associated with a significant increase in hospitalization rates for first-time AMI with comorbid DM, compared to respective rates in populations not exposed to POPs.