Workers in Australian prebake aluminium smelters: update on risk of mortality and cancer incidence in the Healthwise cohort.

OBJECTIVES: To investigate mortality and the rates of incident cancer among a cohort of aluminium industry workers. METHODS: Among 4507 male employees who worked in either of two Australian prebake smelters for at least 3 months, data linkage was undertaken with the Australian National Death Index and Australian Cancer Database. Standardised Mortality Ratios (SMRs) and Standardised Incidence Rates (SIRs) were estimated for the whole cohort and for: production; maintenance and office workers. SMRs and SIRs were calculated by time since first employment. RESULTS: Among production workers, there was an excess risk of mortality from mesothelioma (SMR 2.8, 95% CI 1.3 to 5.2), lung (SMR 1.4, 95% CI 1.0 to 1.8), prostate (SMR 1.9, 95% CI 1.3 to 2.7) and liver cancer (SMR 2.0, 95% CI 1.1 to 3.4) and the SIR was also increased for overall respiratory cancers, specifically lung cancers. An excess risk of death from stomach cancer (SMR 2.9, 95% CI 1.2 to 6.1) and Alzheimer's disease (SMR 3.4, 95% CI 1.1 to 7.9) was seen among maintenance workers. The overall risk of death was similar to that of the Australian general population, as was mortality from cancers overall and non-malignant respiratory disease. CONCLUSIONS: No excess risk of death from bladder cancer or non-malignant respiratory disease was found. Excess lung cancer mortality and incidence may be explained by smoking and excess mortality from mesothelioma may be explained by asbestos exposure. An excess risk of mortality from liver and prostate cancer has been shown in production workers and requires further investigation.

Predictive value of non-specific bronchial challenge testing for respiratory symptoms and lung function in aluminium smelter workers.

OBJECTIVE: To assess the predictive value of bronchial hyper-responsiveness (BHR) for the subsequent development of respiratory symptoms, airflow limitation and decline in lung function among aluminium smelter workers. METHODS: An inception cohort study of new employees at two Australian aluminium smelters was conducted. Participants completed a modified British Medical Research Council respiratory questionnaire, spirometry and a methacholine bronchial challenge test at baseline and at annual follow-up reviews. BHR was defined as PD20 ≤4000 µg. Poisson and mixed effects models were fitted to respiratory symptoms and lung function (forced expiratory volume in 1 s (FEV1) and FEV1/forced vital capacity (FVC)). RESULTS: Baseline interview and lung function testing were completed by 278 workers, who were followed for a median of 4 years. BHR at baseline, present in 82 workers, was not associated with incident wheeze risk ratio (RR)=1.07 (95% CI 0.74 to 1.55) and cough RR=0.78 (95% CI 0.45, 1.35), but there was some increased risk of chest tightness RR=1.40 (95% CI 0.99, 1.98) after adjustment for age, sex, smoking and atopy. BHR at baseline was associated with lower FEV1 and FVC, although the rate of annual decline in FEV1 or FVC was similar between those with or without BHR. The specificity of BHR was 77% for wheeze, 70% for cough and 77% for chest tightness, but the sensitivity was poor, at 33%, 24% and 39%, respectively. CONCLUSION: Methacholine challenge testing at entry to employment was not sufficiently predictive of later adverse respiratory outcomes, and notwithstanding the study limitations is unlikely to be a useful pre-employment or preplacement screening test in the aluminium smelting industry.

Respiratory outcomes among refinery workers exposed to inspirable alumina dust: A longitudinal study in Western Australia.

BACKGROUND: Information is scarce about the occupational health effects of exposure to alumina dust. This study examines the respiratory effects of inspirable alumina dust exposure in alumina refineries. METHODS: An inception cohort study at three alumina refineries in Western Australia recruited 416 participants (351 males, 65 females) between 1995 and 2000 who were followed up annually until 2008 or until exit from study. At each health interview a respiratory questionnaire and lung function test was undertaken, measuring forced expiratory volume in one second (FEV1 ) and forced vital capacity (FVC). Participants provided job histories which were combined with air monitoring data to calculate cumulative exposure to inspirable alumina dust (mg/m3 -years). Generalized estimating equations with Poisson distribution and mixed effects models were used to examine the effects of alumina exposure. RESULTS: The number of exposed participants was relatively small (n = 82, 19.7%). There was no association between alumina dust exposure and prevalence of cough, wheeze or rhinitis. No associations were found between measures of lung function and tertiles of alumina exposure in the first two follow-ups, or the whole follow-up period, though there was a suggestive dose-response trend across exposed groups for decline in absolute FEV1 (p for trend = .06). For mean annual change in FEV1 and FVC based on the first three follow-ups it was not possible to rule out an effect above a threshold level of exposure. CONCLUSION: There is no evidence of an association between exposure to alumina and the reporting of respiratory symptoms but some evidence for an effect on lung function.

Mortality and cancer incidence among female Australian firefighters.

OBJECTIVES: To investigate the mortality and cancer incidence of female firefighters, a group where there are limited published findings. METHODS: Participating fire agencies supplied records of individual firefighters including the number and type of incidents attended. The cohort was linked to the Australian National Death Index and Australian Cancer Database. Standardised mortality ratios and standardised cancer incidence ratios were calculated separately for paid and volunteer firefighters. Volunteer firefighters were grouped into tertiles by the duration of service and by a number of incidents attended and relative mortality ratios and relative incidence ratios calculated. RESULTS: For volunteer firefighters (n=37 962), the overall risk of mortality and risk from all major causes of death were reduced when compared with the general population whether or not they had ever attended incidents. Volunteer firefighters had a similar cancer incidence when compared with the general population for most major cancer categories. Female volunteer firefighters have usually attended few fires. Of those who had turned out to incidents, only one-third had attended more than 12 fires about half the number for male volunteers. Mortality and cancer incidence for paid female firefighters (n=1682) were similar to the general population but the numbers were small and so power was limited. CONCLUSIONS: Female volunteer firefighters have a cancer incidence similar to the general population but a reduced risk of mortality which is likely to be a result of a 'healthy volunteer' effect.Most of the paid female firefighters were relatively recent recruits and it will be important to monitor the health of this group as more women are recruited to front-line firefighting roles.

Mortality and cancer incidence among male volunteer Australian firefighters.

OBJECTIVES: This study aims to investigate mortality and cancer incidence of Australian male volunteer firefighters and of subgroups of firefighters by duration of service, era of first service and the number and type of incidents attended. METHODS: Participating fire agencies supplied records of individual volunteer firefighters, including incidents attended. The cohort was linked to the Australian National Death Index and Australian Cancer Database. standardised mortality ratios (SMRs) and standardised incidence ratios (SIRs) for cancer were calculated. Firefighters were grouped into tertiles by duration of service and by number of incidents attended and relative mortality ratios and relative incidence ratios calculated. RESULTS: Compared with the general population, there were significant decreases in overall cancer incidence and in most major cancer categories. Prostate cancer incidence was increased compared with the general population, but this was not related to the number of incidents attended. Kidney cancer was associated with increased attendance at fires, particularly structural fires.The overall risk of mortality was significantly decreased, and all major causes of death were significantly reduced for volunteer firefighters. There was evidence of an increased mortality from ischaemic heart disease, with increased attendance at fires. CONCLUSION: Volunteer firefighters have a reduced risk of mortality and cancer incidence compared with the general population, which is likely to be a result of a 'healthy-volunteer' effect and, perhaps, lower smoking rates.

Longitudinal analysis of respiratory outcomes among bauxite exposed workers in Western Australia.

INTRODUCTION: Occupational exposure to bauxite is common in the aluminium industry but little is known about the associated health effects. This study investigates respiratory health in relation to respirable bauxite dust exposure longitudinally over a 13 year period. METHODS: An inception cohort study recruited 91 male bauxite miners and 363 male alumina refinery workers. Annual measurements of respiratory symptoms and lung function were made. Cumulative exposure to bauxite was derived from job histories and air monitoring data. Mixed-effects modeling was used. RESULTS: No associations were found between cumulative bauxite exposure and respiratory symptoms or lung function. However, when analysis was restricted to the first three rounds, FEV1 was significantly lower in all exposure groups than in those unexposed but with no significant trend. CONCLUSION: Increasing exposure to bauxite dust in the aluminum industry was not associated with respiratory symptoms or consistent decrements in lung function.

Long-term impact of exposure to coalmine fire emitted PM2.5 on emergency ambulance attendances.

BACKGROUND: Little is known about the long-term health effects of coalmine fire smoke exposure. The 2014 Hazelwood coalmine fire event in southeast Australia released smoke into surrounding areas for 6 weeks. OBJECTIVES: We aimed to investigate whether individual-level exposure to coalmine fire-related PM2.5 was associated with a long-term increase in ambulance attendances following a coalmine fire event. METHODS: A total of 2223 residents from the most exposed town of Morwell were assessed for ambulance attendances after the Hazelwood event from April 1, 2014 to December 31, 2017. PM2.5 exposure was estimated for each individual using participant self-reported location diary data during the event and modelled PM2.5 concentrations. Recurrent event survival analysis was used to evaluate the relationship between PM2.5 exposure and ambulance attendances. RESULTS: For each 10 µg/m3 increase in mean coalmine fire-related PM2.5 exposure, there was a 10% (adjusted hazard ratio [HR]:1.10, 95%CI:1.03-1.17) increase in the overall risk of ambulance attendances within 3.5 years after the coalmine fire. Exposure to PM2.5 was also associated with increased risk of respiratory (HR: 1.21, 95%CI: 1.02-1.44) and cardiovascular (HR: 1.13, 95%CI: 1.01-1.28) related ambulance attendances. CONCLUSION: These results demonstrate that exposure to coalmine fire smoke during the Hazelwood event was associated with a long-term health risk post the fire event, specifically for respiratory and cardiovascular conditions. These findings are important for effective implementation of health care services following future extended coalmine fire PM2.5 events.

Associations between self-reported respiratory symptoms and non-specific psychological distress following exposure to a prolonged landscape fire.

We investigated the association between respiratory symptoms and psychological distress in the context of a prolonged smoke event, and evaluated whether smoke exposure, or pre-existing respiratory and mental health conditions, influenced the association. Three thousand ninety-six residents of a rural town heavily exposed to smoke from the 6-week Hazelwood coal mine fire, and 960 residents of a nearby unexposed town, completed Kessler's psychological distress questionnaire (K10) and a modified European Community Respiratory Health Survey. Logistic regression models evaluated associations between distress and respiratory symptoms, with interactions fitted to evaluate effect modification. Smoke exposed participants reported higher levels of distress than those unexposed, and participants reporting respiratory symptoms recorded higher levels of distress than participants without respiratory symptoms, irrespective of exposure. 5-unit increments in K10 scores were associated with 21%-48% increases in the odds of reporting respiratory symptoms. There were significant interactions with pre-existing asthma, chronic obstructive pulmonary disease and mental health conditions, but not with smoke exposure. Although participants with pre-existing conditions were more likely to report respiratory symptoms, increasing distress was most strongly associated with respiratory symptoms among those without pre-existing conditions. Communities exposed to landscape fire smoke could benefit from interventions to reduce both psychological and respiratory distress.

Impacts of High Concentration, Medium Duration Coal Mine Fire Related PM2.5 on Cancer Incidence: 5-Year Follow-Up of the Hazelwood Health Study.

No studies have investigated the cancer outcomes from high level medium duration coal mine fire fine particulate matter ⩽2.5 µm in diameter (PM2.5) exposure. We included 2208 Morwell residents (exposed) and 646 Sale residents (unexposed) who participated in the Hazelwood Health Study Adult Survey. Competing risk regression models were used to evaluate relationships between coal mine fire exposure and cancer incidence, adjusting for known confounders. There were 137 cancers in the exposed and 27 in the unexposed over 14 849 person-years of follow-up. A higher risk of cancer incidence was observed for Morwell participants (HR = 1.67 [95% CI 1.05-2.67]), but no evidence to suggest associations between PM2.5 exposure and incidence of all cancers (HR = 1.02 [95% CI 0.91-1.13]), or site-specific cancers. There is no strong evidence that exposure to high concentrations of mine fire-related PM2.5 over a prolonged period could explain the higher risk in exposed population in this study.

Caustic Mist Exposure and Respiratory Outcomes in a Cohort Study of Alumina Refinery Workers.

A common chemical exposure in alumina refining is caustic mist. Although recognized as a strong airways irritant, little is known of the chronic respiratory effects of caustic mist in alumina refining. A suitable metric for caustic mist exposure assessment in alumina refining for epidemiological purposes has not been identified. Peak exposure is likely to be important, but is difficult to assess in epidemiological studies. In this study, we investigate the respiratory effects of caustic mist in an inception cohort (n = 416) of alumina refinery workers and describe the development and use of a peak exposure metric for caustic mist. We then compare the results with a metric based on duration of exposure. Participants were interviewed annually about respiratory symptoms and had a lung function test. Job history data were collected from each interview and levels of caustic mist were measured periodically by air monitoring. We found a weak association between the caustic mist peak exposure metric and reported cough (P for linear trend = 0.079) with the highest peak exposure group odds ratio = 2.32 (95% confidence interval: 1.27, 4.22). For lung function, we found declines in the forced expiratory volume in 1 second and forced vital capacity for changes in annual and absolute lung function for both metrics of exposure, but only the ratio of absolute lung function was statistically associated with an increasing duration of caustic exposure (P for linear trend = 0.011). In this cohort, we did not observe an association with respiratory symptoms or consistent decrements in lung function. There was little difference between the exposure metrics used for investigation of the chronic effects from caustic mist.

Is potroom asthma due more to sulphur dioxide than fluoride? An inception cohort study in the Australian aluminium industry.

OBJECTIVES: Although an asthma-like syndrome has been recognised in aluminium smelter workers for over 70 years, the causal agent has been difficult to identify. METHODS: An inception cohort study was conducted at two Australian aluminium smelters where 446 employees participated over a period of 9 years. Cumulative exposures between interviews were estimated from job histories using a task exposure matrix based on measurements in the smelters. Participants completed an MRC respiratory questionnaire, spirometry and methacholine challenge test. Data were analysed with generalised estimating equations to allow for repeated measurements of each participant. RESULTS: Wheeze and chest tightness, the two symptoms most closely related to asthma, showed associations with occupational exposures. SO(2) exposure was significantly associated with these symptoms, bronchial hyper-responsiveness (BHR) to methacholine (a feature of asthma), airflow limitation (reduced forced expiratory volume in 1 second/forced vital capacity ratio) and longitudinal decline in lung function. Fluoride exposure was associated with the same outcomes, but less strongly. Inhalable dust and the benzene soluble fraction (BSF) were associated with symptoms of asthma and BHR. Although many of the exposures were highly correlated, further modelling suggested that of the known respiratory irritants, SO(2) was more likely than fluoride to be primarily responsible for the symptoms observed. Fluoride, inhalable dust and SO(2) were the most important airborne contaminants associated with effects on lung function. CONCLUSIONS: The observed effects were detected at contaminant levels within occupational exposure standards, so further reductions are required, particularly in SO(2) exposures.

Fractional polynomials and model selection in generalized estimating equations analysis, with an application to a longitudinal epidemiologic study in Australia.

In epidemiologic studies, researchers often need to establish a nonlinear exposure-response relation between a continuous risk factor and a health outcome. Furthermore, periodic interviews are often conducted to take repeated measurements from an individual. The authors proposed to use fractional polynomial models to jointly analyze the effects of 2 continuous risk factors on a health outcome. This method was applied to an analysis of the effects of age and cumulative fluoride exposure on forced vital capacity in a longitudinal study of lung function carried out among aluminum workers in Australia (1995-2003). Generalized estimating equations and the quasi-likelihood under the independence model criterion were used. The authors found that the second-degree fractional polynomial models for age and fluoride fitted the data best. The best model for age was robust across different models for fluoride, and the best model for fluoride was also robust. No evidence was found to suggest that the effects of smoking and cumulative fluoride exposure on change in forced vital capacity over time were significant. The trend 1 model, which included the unexposed persons in the analysis of trend in forced vital capacity over tertiles of fluoride exposure, did not fit the data well, and caution should be exercised when this method is used.

Relationship between cardiopulmonary mortality and cancer risk and quantitative exposure to polycyclic aromatic hydrocarbons, fluorides, and dust in two prebake aluminum smelters.

OBJECTIVES: We examined the risk of mortality and cancer incidence with quantitative exposure to benzene-soluble fraction (BSF), benzo(a)pyrene (BaP), fluoride, and inhalable dust in two Australian prebake smelters. METHODS: A total of 4,316 male smelter workers were linked to mortality and cancer incidence registries and followed from 1983 through 2002 (mean follow-up: 15.9 years, maximum: 20 years). Internal comparisons using Poisson regression were undertaken based on quantitative exposure levels. RESULTS: Smoking-adjusted, monotonic relationships were observed between respiratory cancer and cumulative inhalable dust exposure (trend p = 0.1), cumulative fluoride exposure (p = 0.1), and cumulative BaP exposure (p = 0.2). The exposure-response trends were stronger when examined across the exposed categories (BaP p = 0.1; inhalable dust p = 0.04). A monotonic, but not statistically significant trend was observed between cumulative BaP exposure and stomach cancer (n = 14). Bladder cancer was not associated with BaP or BSF exposure. No other cancer and no mortality outcomes were associated with these smelter exposures. CONCLUSIONS: The carcinogenicity of Söderberg smelter exposures is well established; in these prebake smelters we observed an association between smelter exposures and respiratory cancer, but not bladder cancer. The exploratory finding for stomach cancer needs confirmation. These results are preliminary due to the young cohort and short follow-up time.

Associations between Respiratory Health Outcomes and Coal Mine Fire PM2.5 Smoke Exposure: A Cross-Sectional Study.

In 2014, wildfires ignited a fire in the Morwell open cut coal mine, Australia, which burned for six weeks. This study examined associations between self-reported respiratory outcomes in adults and mine fire-related PM2.5 smoke exposure. Self-reported data were collected as part of the Hazelwood Health Study Adult Survey. Eligible participants were adult residents of Morwell. Mine fire-related PM2.5 concentrations were provided by the Commonwealth Scientific and Industrial Research Organisation Oceans & Atmosphere Flagship. Personalised mean 24-h and peak 12-h mine fire-related PM2.5 exposures were estimated for each participant. Data were analysed by multivariate logistic regression. There was some evidence of an association between respiratory outcomes and mine fire PM2.5 exposure. Chronic cough was associated with an odds ratio (OR) of 1.13 (95% confidence interval 1.03 to 1.23) per 10 µg/m3 increment in mean PM2.5 and 1.07 (1.02 to 1.12) per 100 µg/m3 increment in peak PM2.5. Current wheeze was associated with peak PM2.5, OR = 1.06 (1.02 to 1.11) and chronic phlegm with mean PM2.5 OR = 1.10 (1.00 to 1.20). Coal mine PM2.5 smoke exposure was associated with increased odds of experiencing cough, phlegm and wheeze. Males, participants 18-64 years, and those residing in homes constructed from non-brick/concrete materials or homes with tin/metal roofs had higher estimated ORs. These findings contribute to the formation of public health policy responses.

All cause mortality and incidence of cancer in workers in bauxite mines and alumina refineries.

Bauxite is a reddish clay that is refined to produce alumina, which is then reduced to aluminium. There have been studies examining the health of workers in aluminium smelters, but not workers in bauxite mining and alumina refining. A cohort of employees of 1 large aluminium company since 1983 was assembled (n = 6,485, 5,828 men). Deaths and incident cancers to 2002 were ascertained by linkage to national and state cancer and death registries. SIRs and SMRs were calculated compared to national rates standardizing for calendar year, sex and 5-year age group. The mortality from all causes (SMR 0.68, 95% CI: 0.60-0.77), and from circulatory and respiratory diseases, all cancers combined and injury in the male cohort were lower than in the Australian male population and were similar across work groups and with duration of employment. The only significant increased mortality risk was from pleural mesothelioma. The incidence of all cancers combined was similar to the Australian rate. The cohort had a lower risk of incident lymphohaematopoietic cancer (SIR 0.50, 95% CI: 0.31-0.88) and a higher risk of melanoma (SIR 1.30, 95% CI: 1.00-1.69) although no dose-responses were seen. There was also an increased risk of mesothelioma (SIR 3.49, 95% CI: 1.82-6.71), which was associated with exposures outside the aluminium industry. This study is the first to examine cancer and mortality amongst workers in bauxite mines and alumina refineries and found little evidence for increased cancer incidence or mortality in these workers.

Comparison of first, last, and longest-held jobs as surrogates for all jobs in estimating cumulative exposure in cross-sectional studies of work-related asthma.

BACKGROUND: Previous occupational studies have used exposure in most recent job as a surrogate for all jobs or "total work history" exposure. This method may not be valid for diseases in which disability brought on by one job may influence later work history, such as asthma. We investigated different surrogates for total work history for the outcome of asthma symptoms. METHODS: In a cross-sectional study, we quantitatively compared three exposure surrogates (last job, first job, and longest-held job) with the total cumulative work exposure (all jobs) in a cohort of 1778 aluminium industry workers. The chemical exposures we compared were total fluoride dust, inspirable dust, and sulfur dioxide with the respiratory symptoms of wheeze, chest tightness, and rhinitis. RESULTS: When extrapolated over time, all surrogates quantitatively overestimated the gold standard "all jobs" for all three exposures investigated. For the symptom of wheeze, last job was found to be the worst surrogate for all jobs for the three exposure types investigated. Prevalence ratios for fluoride exposure and the symptom of occupational wheeze were last job 1.07 (95% confidence interval, 0.92-1.26), longest job 1.10 (0.94-1.30), first job 1.14 (0.97-1.35), and all jobs 1.27 (1.05-1.53). CONCLUSIONS: Although last job has been found to be a satisfactory surrogate for all jobs in cancer studies, we do not recommend the use of this metric in studies of chronic diseases where development of disability may occur with early exposure. We found that both first job and longest job held were better metrics in studies where the adverse health effect may influence the job history of subject.

Methodological issues in linking study participants to Australian cancer registries using different methods: lessons from a cohort study.

OBJECTIVE: To compare results of concurrent linkage of records from the same occupational cohort to cancer registries at both a State and national level. Methodological issues affecting the record registry linkage process will be explored in cases of discordant results between the State and national cancer linkages. METHODS: The number of incident invasive cancers in an occupational cohort of more than 11,000 workers was determined by linkage to the National Cancer Statistics Clearing House (NCSCH) in 2003. The results were then compared with linkages by the cancer registries of Victoria and Western Australia in 2004, and also with a previous NCSCH linkage in 1998. RESULTS: Our analyses show an under-ascertainment of confirmed cancer cases by the NCSCH of about 13% (26/205) in Victoria and 11% (32/297) in Western Australia. In addition, 14 cases (5%) identified in a previous NCSCH record linkage in 1998 were not matched in 2003. CONCLUSIONS: These findings strongly indicate that record linkage to the State cancer registries was essential to maximise the ascertainment of cancer cases in our cohort. We attribute the discordant linkage results to differences in the quality of the record linkage process by the cancer registries. IMPLICATIONS: The record linkage methods of the national and State cancer registries need further standardisation. At present it is advisable to perform cancer record linkages through the State registries in addition to or instead of the NCSCH.

Impact of Fine Particulate Matter (PM2.5) Exposure During Wildfires on Cardiovascular Health Outcomes.

BACKGROUND: Epidemiological studies investigating the role of fine particulate matter (PM2.5; aerodynamic diameter <2.5 µm) in triggering acute coronary events, including out-of-hospital cardiac arrests and ischemic heart disease (IHD), during wildfires have been inconclusive. METHODS AND RESULTS: We examined the associations of out-of-hospital cardiac arrests, IHD, acute myocardial infarction, and angina (hospital admissions and emergency department attendance) with PM2.5 concentrations during the 2006-2007 wildfires in Victoria, Australia, using a time-stratified case-crossover study design. Health data were obtained from comprehensive health-based administrative registries for the study period (December 2006 to January 2007). Modeled and validated air exposure data from wildfire smoke emissions (daily average PM2.5, temperature, relative humidity) were also estimated for this period. There were 457 out-of-hospital cardiac arrests, 2106 emergency department visits, and 3274 hospital admissions for IHD. After adjusting for temperature and relative humidity, an increase in interquartile range of 9.04 µg/m(3) in PM2.5 over 2 days moving average (lag 0-1) was associated with a 6.98% (95% CI 1.03% to 13.29%) increase in risk of out-of-hospital cardiac arrests, with strong association shown by men (9.05%,95%CI 1.63% to 17.02%) and by older adults (aged ≥65 years) (7.25%, 95% CI 0.24% to 14.75%). Increase in risk was (2.07%, 95% CI 0.09% to 4.09%) for IHD-related emergency department attendance and (1.86%, 95% CI: 0.35% to 3.4%) for IHD-related hospital admissions at lag 2 days, with strong associations shown by women (3.21%, 95% CI 0.81% to 5.67%) and by older adults (2.41%, 95% CI 0.82% to 5.67%). CONCLUSION: PM2.5 exposure was associated with increased risk of out-of-hospital cardiac arrests and IHD during the 2006-2007 wildfires in Victoria. This evidence indicates that PM2.5 may act as a triggering factor for acute coronary events during wildfire episodes.

Forest Fire Smoke Exposures and Out-of-Hospital Cardiac Arrests in Melbourne, Australia: A Case-Crossover Study.

BACKGROUND: Millions of people can potentially be exposed to smoke from forest fires, making this an important public health problem in many countries. OBJECTIVE: In this study we aimed to measure the association between out-of-hospital cardiac arrest (OHCA) and forest fire smoke exposures in a large city during a severe forest fire season, and estimate the number of excess OHCAs due to the fire smoke. METHODS: We investigated the association between particulate matter (PM) and other air pollutants and OHCA using a case-crossover study of adults (≥ 35 years of age) in Melbourne, Australia. Conditional logistic regression models were used to derive estimates of the percent change in the rate of OHCA associated with an interquartile range (IQR) increase in exposure. From July 2006 through June 2007, OHCA data were collected from the Victorian Ambulance Cardiac Arrest Registry. Hourly air pollution concentrations and meteorological data were obtained from a central monitoring site. RESULTS: There were 2,046 OHCAs with presumed cardiac etiology during our study period. Among men during the fire season, greater increases in OHCA were observed with IQR increases in the 48-hr lagged PM with diameter ≤ 2.5 µm (PM2.5) (8.05%; 95% CI: 2.30, 14.13%; IQR = 6.1 µg/m(3)) or ≤ 10 µm (PM10) (11.1%; 95% CI: 1.55, 21.48%; IQR = 13.7 µg/m(3)) and carbon monoxide (35.7%; 95% CI: 8.98, 68.92%; IQR = 0.3 ppm). There was no significant association between the rate of OHCA and air pollutants among women. One hundred seventy-four "fire-hours" (i.e., hours in which Melbourne's air quality was affected by forest fire smoke) were identified during 12 days of the 2006/2007 fire season, and 23.9 (95% CI: 3.1, 40.2) excess OHCAs were estimated to occur due to elevations in PM2.5 during these fire-hours. CONCLUSIONS: This study found an association between exposure to forest fire smoke and an increase in the rate of OHCA. These findings have implications for public health messages to raise community awareness and for planning of emergency services during forest fire seasons.