Diesel exhaust and lung cancer in the trucking industry: exposure-response analyses and risk assessment

Dose-response-relationship between occupational exposure to diesel engine emissions and lung cancer risk: A systematic review and meta-analysis

BACKGROUND

In 2012, the International Agency for Research on Cancer (IARC) concluded that diesel engine emissions (DEE) emissions cause cancer in humans. However, there is still controversy surrounding this conclusion, due to several studies since the IARC decision citing a lack of evidence of a dose-response relationship.

OBJECTIVES

Through a systematic review, we aimed to evaluate all evidence on the association between occupational DEE and lung cancer to investigate whether there is an increased risk of lung cancer for workers exposed to DEE and if so, to describe the dose-response relationship.

METHODS

We registered the review protocol with PROSPERO and searched for observational studies in relevant literature databases. Two independent reviewers screened the studies' titles/abstracts and full texts, and extracted and assessed their quality. Studies with no direct DEE measurement but with information on length of exposure for high-risk occupations were assigned exposure values based on the DEE Job-Exposure-Matrix (DEE-JEM). After assessing quality and informativeness, we selected appropriate studies for the dose-response meta-analysis.

RESULTS

Sixty-five reports (from thirty-seven studies) were included in the review; one had a low risk of bias (RoB) (RR per 10 μg/m3-years: 1.014 [95%CI 1.007-1.021]). There was an increased, statistically significant risk of lung cancer with increasing DEE exposure for all studies (RR per 10 μg/m3-years = 1.013 [95%CI 1.004-1.021]) as well as for studies with a low RoB in the exposure category (RR per 10 μg/m3-years = 1.008 [95% CI1.001-1.015]). We obtained a doubling dose of 555 μg/m3-years for all studies and 880 μg/m3-years for studies with high quality in the exposure assessment.

DISCUSSION

We found a linear positive dose-response relationship for studies with high quality in the exposure domain, even though all studies had an overall high risk of bias. Current threshold levels for DEE exposure at the workplace should be reconsidered.

Oxygenated Diesel Fuels and Their Effect on PM Emissions

Particulate matter (PM) emitted by diesel engines is one of the most harmful components of exhaust gases, including its carcinogenic effect. Due to the widespread use of diesel engines, the health effects of PM emissions affect millions of people around the world. At the same time, diesel particulate matter is characterized by a very complicated structure and mechanisms of formation compared to other exhaust gas components. It is obvious that PM emissions should be limited by all means. This article focuses on the reduction of PM emissions with the use of oxygenated fuels. The mechanisms of oxygenated fuels influence on the soot formation process in the working process of diesel engines have been discussed. The importance of the chemical structure of oxygenated compounds for the effectiveness of PM emissions reduction was considered. The results of empirical research on the influence on PM emissions of oxygenated fuels containing 12 oxygenates from chemical groups such as glycol ethers, maleates, carbonates and butanol were analyzed. The emissions tests were undertaken on a diesel passenger car over the NEDC and FTP-75 cycles. The results showed a high potential of oxygenated fuels in PM emissions reduction, even at a low oxygenates concentration of 5% v/v; namely, PM emissions were reduced by up to 32%. According to tests results, 1% of oxygen in the fuel resulted in an average reduction of PM emissions by 7% to 10%. In the view of already limited possibilities of modifying conventional parameters of diesel fuels, the use of oxygenated compounds is a promising way to trade on the potential of fuels in PM emissions reduction.

Impact of Unsustainable Environmental Conditions Due to Vehicular Emissions on Associated Lifetime Cancer Risk in India: A Novel Approach

The Indian Western Himalayas (IWHs) are a world famous tourist spot, and every year millions of tourists visit this area in fossil fuel-driven vehicles. Emissions from these vehicles persistently deteriorate the pristine environment of the IWHs. Therefore, in the current study, efforts were made to assess the compromised environmental conditions of Manali, Himachal Pradesh, India that resulted from the inflow of tourists and the activities undertaken by them. This study revealed that Manali could sustainably accommodate only 0.305 M tourists/month, and this threshold was reported to be crossed in the months of April, May and June. Furthermore, to augment these findings, water and ambient air samples were collected and analyzed for the presence of elemental carbon (EC) from one of the medium tourism potential regions of Manali, i.e., the Hamta glacier. The tributary receiving water from the Hamta glacier and the ambient air of the area was observed to be contaminated with 42 ± 12 ppb and 880 ± 43 µg m⁻³ of EC, respectively. It was observed that the inhalation and ingestion of EC-contaminated air and water could jeopardize human health due to a high lifetime cancer risk. However, without the intervention of eco-tourism in the study area, higher environmental health effects were also speculated. The observations made in this study are expected to trigger the interests of the researchers, international scientific community and regional authorities working towards the unsustainable development of the IWHs and deteriorating environmental conditions.

Diesel Engine Exhaust Exposure in the Ontario Civil Infrastructure Construction Industry

OBJECTIVES

Diesel engine exhaust (DEE) is a known lung carcinogen and a common occupational exposure in Canada. The use of diesel-powered equipment in the construction industry is particularly widespread, but little is known about DEE exposures in this work setting. The objective of this study was to determine exposure levels and identify and characterize key determinants of DEE exposure at construction sites in Ontario.

METHODS

Elemental carbon (EC, a surrogate of DEE exposure) measurements were collected at seven civil infrastructure construction worksites and one trades training facility in Ontario using NIOSH method 5040. Full-shift personal air samples were collected using a constant-flow pump and SKC aluminium cyclone with quartz fibre filters in a 37-mm cassette. Exposures were compared with published health-based limits, including the Dutch Expert Committee on Occupational Safety (DECOS) limit (1.03 µg m-3 respirable EC) and the Finnish Institute of Occupational Health (FIOH) recommendation (5 µg m-3 respirable EC). Mixed-effects linear regression was used to identify determinants of EC exposure.

RESULTS

In total, 149 EC samples were collected, ranging from <0.25 to 52.58 µg m-3 with a geometric mean (GM) of 3.71 µg m-3 [geometric standard deviation (GSD) = 3.32]. Overall, 41.6% of samples exceeded the FIOH limit, mostly within underground worksites (93.5%), and 90.6% exceeded the DECOS limit. Underground workers (GM = 13.20 µg m-3, GSD = 1.83) had exposures approximately four times higher than below grade workers (GM = 3.56 µg m-3, GSD = 1.94) and nine times higher than above ground workers (GM = 1.49 µg m-3, GSD = 1.75). Training facility exposures were similar to above ground workers (GM = 1.86 µg m-3, GSD = 4.12); however, exposures were highly variable. Work setting and enclosed cabins were identified as the key determinants of exposure in the final model (adjusted R2 = 0.72, P < 0.001). The highest DEE exposures were observed in underground workplaces and when using unenclosed cabins.

CONCLUSIONS

This study provides data on current DEE exposure in Canadian construction workers. Most exposures were above recommended health-based limits, albeit in other jurisdictions, signifying a need to further reduce DEE levels in construction. These results can inform a hazard reduction strategy including targeted intervention/control measures to reduce DEE exposure and the burden of occupational lung cancer.

Diesel Engine Exhaust Exposure, Smoking, and Lung Cancer Subtype Risks. A Pooled Exposure-Response Analysis of 14 Case-Control Studies

Rationale: Although the carcinogenicity of diesel engine exhaust has been demonstrated in multiple studies, little is known regarding exposure-response relationships associated with different exposure subgroups and different lung cancer subtypes.Objectives: We expanded on a previous pooled case-control analysis on diesel engine exhaust and lung cancer by including three additional studies and quantitative exposure assessment to evaluate lung cancer and subtype risks associated with occupational exposure to diesel exhaust characterized by elemental carbon (EC) concentrations.Methods: We used a quantitative EC job-exposure matrix for exposure assessment. Unconditional logistic regression models were used to calculate lung cancer odds ratios and 95% confidence intervals (CIs) associated with various metrics of EC exposure. Lung cancer excess lifetime risks (ELR) were calculated using life tables accounting for all-cause mortality. Additional stratified analyses by smoking history and lung cancer subtypes were performed in men.Measurements and Main Results: Our study included 16,901 lung cancer cases and 20,965 control subjects. In men, exposure response between EC and lung cancer was observed: odds ratios ranged from 1.09 (95% CI, 1.00-1.18) to 1.41 (95% CI, 1.30-1.52) for the lowest and highest cumulative exposure groups, respectively. EC-exposed men had elevated risks in all lung cancer subtypes investigated; associations were strongest for squamous and small cell carcinomas and weaker for adenocarcinoma. EC lung cancer exposure response was observed in men regardless of smoking history, including in never-smokers. ELR associated with 45 years of EC exposure at 50, 20, and 1 μg/m3 were 3.0%, 0.99%, and 0.04%, respectively, for both sexes combined.Conclusions: We observed a consistent exposure-response relationship between EC exposure and lung cancer in men. Reduction of workplace EC levels to background environmental levels will further reduce lung cancer ELR in exposed workers.

Environmental and occupational determinants of lung cancer

Lung cancer has become a global problem, from a rare disease to an emerging public health issue. The current data of GLOBOCAN 2018, indicates that this disease has recorded highest mortality among all types of cancer. The etiological factors of lung cancer have become more multiplex because of increasing industrialization and environmental pollution around the world, especially in India. There is a rise in incidence of lung cancer among non-smokers and this can be attributed to environmental and occupational exposure to various kinds of hazardous substances. Target mutations are high in Lung cancer among non-smokers when compared to smokers. Some developed countries have guidelines and policies for prevention and control of risk factors focusing on these issues. Intervention aiming for primary prevention can be an important and cost-effective tool in developing countries to deal with increasing incidence of lung cancer. There is a need to define high risk group among non-smokers after taking into account environmental and occupational determinants as important risk factors. Research on etiology of lung cancer and prevention provides evidence to work on global incidence and prevalence of lung cancer, and for designing cost effective lung cancer prevention strategies. Research in the area of lung cancer prevention should be considered to recognize the areas where action is required to prevent environment and occupation related lung cancer. The government and occupational health and safety organizations have taken many steps in the last few years that can help to protect workers from these exposures. But the dangers are still there, so there is a need to do more to limit these exposures around workplace. This whole situation guides us to advocate population-based intervention along with policy implementation.

Diesel Exhaust and Lung Cancer-Aftermath of Becoming an IARC Group 1 Carcinogen

The International Agency for Research on Cancer reclassified diesel exhaust from Group 2A (probably carcinogenic to humans) to Group 1 (carcinogenic to humans) in 2012. Since then, reevaluation and reanalysis of 2 major studies (Diesel Exhaust in Miners Study and Trucking Industry Particle Study) that were influential to the International Agency for Research on Cancer evaluation have replicated the original findings and demonstrated the suitability of these epidemiologic data for the quantitative risk assessment needed to set safe exposure limits in occupational and outdoor ambient environments. The challenge now is to protect the workers and general populations in urban areas from the carcinogenicity of diesel exhaust.

Burden of lung cancer attributable to occupational diesel engine exhaust exposure in Canada

Objective

To estimate the population attributable fraction (PAF) and number of incident and fatal lung cancers in Canada from occupational exposure to diesel engine exhaust (DEE).

Methods

DEE exposure prevalence and level estimates were used with Canadian Census and Labour Force Survey data to model the exposed population across the risk exposure period (REP, 1961–2001). Relative risks of lung cancer were calculated based on a meta-regression selected from the literature. PAFs were calculated using Levin’s equation and applied to the 2011 lung cancer statistics obtained from the Canadian Cancer Registry.

Results

We estimated that 2.4% (95% CI 1.6% to 6.6%) of lung cancers in Canada are attributable to occupational DEE exposure, corresponding to approximately 560 (95% CI 380 to 1570) incident and 460 (95% CI 310 to 1270) fatal lung cancers in 2011. Overall, 1.6 million individuals alive in 2011 were occupationally exposed to DEE during the REP, 97% of whom were male. Occupations with the highest burden were underground miners, truck drivers and mechanics. Half of the attributable lung cancers occurred among workers with low exposure.

Conclusions

This is the first study to quantify the burden of lung cancer attributable to occupational DEE exposure in Canada. Our results underscore a large potential for prevention, and a large public health impact from occupational exposure to low levels of DEE.

A task-based analysis of black carbon exposure in Iowa farmers during harvest

Diesel exhaust has been associated with adverse human health effects. Farmers are often exposed to diesel exhaust; however, their diesel exposure has not been well characterized. In this descriptive study, we measured black carbon concentrations as a proxy for diesel exhaust exposure in 16 farmers over 20 sampling days during harvest in southeast Iowa. Farmers wore a personal aethalometer which measured real-time black carbon levels throughout the working day, and their activities were recorded by a field researcher. Black carbon concentrations were characterized for each farmer, and by activity, vehicle fuel type, and microenvironment. Overall, 574 discrete tasks were monitored with a median task duration of 5.5 min. Of these tasks, 39% involved the presence of a diesel vehicle. Farmers' daily black carbon geometric mean exposures ranged from 0.1-2.3 µg/m³, with a median daily geometric mean of 0.3 µg/m³. The highest black carbon concentrations were measured on farmers who used or worked near diesel vehicles (geometric mean ranged from 0.5 µg/m³ while harvesting to 4.9 µg/m³ during animal work). Higher geometric means were found for near vs. far proximity to diesel-fueled vehicles and equipment (2.9 vs. 0.3 µg/m³). Indoor, bystander proximity to diesel-operated vehicles resulted in the highest geometric mean black carbon concentrations (18 µg/m³). Use of vehicles with open cabs had higher mean black carbon concentrations than closed cabs (2.1-3.2 vs. 0.4-0.9 µg/m³). In summary, our study provided evidence that farmers were frequently exposed to black carbon associated with diesel-related activities at levels above urban ambient concentrations in their daily work during harvest.

Lung Function of Grain Millers Exposed to Grain Dust and Diesel Exhaust in Two Food Markets in Ibadan Metropolis, Nigeria

Background

Despite growing concern over occupational exposure to particulate matter (PM) such as grain dust and diesel exhaust, information about the exposure level and health implications among workers in small-scale milling enterprises in developing countries like Nigeria has not been adequately documented. The purpose of this study was to assess the level of exposure to grain dust and diesel exhaust and effect on lung function among grain millers in food markets in Ibadan metropolis, Nigeria.

Methods

The study adopted descriptive cross-sectional design with a comparative approach. Sixteen grain milling shops each were randomly selected from two major food markets in Ibadan metropolis for indoor PM₁₀ and PM_2.5 monitoring. Seventy-two respondents each were proportionately selected from grain millers and shop owners for forced expiratory volume in one second and peak expiratory flow rate tests.

Results

The PM_2.5 concentrations for both market locations ranged between 1,269.3 and 651.7 μg/m³, while PM₁₀ concentrations were between 1,048.2 and 818.1 μg/m³. The recorded concentrations exceeded the World Health Organization guideline limit of 50 μg/m³ and 25 μg/m³ for PM_2.5 and PM₁₀, respectively. As compared with control group (2.1 L), significantly lower forced expiratory volume in one second value (1.61 L) was observed among the exposed group (p < 0.05). Likewise, significantly lower peak expiratory flow rate value (186.7 L/min) was recorded among the exposed group than the control group (269.51 L/min) (p < 0.05).

Conclusion

Exposure to grain dust and diesel exhaust accentuated respiratory disorders with declines in lung functions amongst grain millers. Improved milling practices and engaging cleaner milling facilities should be adopted to minimize exposure and related hazards.

Radon-induced lung cancer deaths may be overestimated due to failure to account for confounding by exposure to diesel engine exhaust in BEIR VI miner studies

BACKGROUND

EPA reported that radon is the second leading cause of lung cancer in the United States, killing 21,100 people per year. EPA relies on the BEIR VI models, based on an evaluation of radon exposure and lung cancer risk in studies of miners. But these models did not account for co-exposure to diesel exhaust, a known human carcinogen recently classified by IARC. It is probable then that a portion of the lung cancer deaths in the miner cohorts are originally attributable to the exposure to diesel rather than radon.

OBJECTIVE

To re-evaluate EPA's radon attributable lung cancer estimates accounting for diesel exposure information in the miner cohorts.

METHODS

We used estimates of historical diesel concentrations, combined with diesel exposure-response functions, to estimate the risks of lung cancer attributable to diesel engine exhaust (DEE) exposure in the miner studies. We re-calculated the fatal lung cancer risk attributable to radon after accounting for risk from diesel and re-estimated the number of U.S. deaths associated with radon in the U.S. using EPA's methodology.

RESULTS

Considering the probable confounding with DEE exposure and using the same estimate of baseline mortality from 1989-91 that the EPA currently uses in their calculations, we estimate that radon-induced lung cancer deaths per year are 15,600 (95% CI: 14,300, 17,000)- 19,300 (95% CI: 18,800, 20,000) in the U.S. population, a reduction of 9%-26%. The death estimates would be 12,900-15,900 using 2014 baseline vital statistics.

CONCLUSIONS

We recommend further research on re-evaluating the health effects of exposure to radon that accounts for new information on diesel exhaust carcinogenicity in BEIR VI models, up-to-date vital statistics and new epidemiological evidence from residential studies.

A critical review of the relationship between occupational exposure to diesel emissions and lung cancer risk

In 2012, a working group of the International Agency for Research on Cancer classified diesel exhaust (DE) as a human carcinogen (Group 1). This decision was primarily based on the findings of the Diesel Exhaust in Miners Study (DEMS). The disparity between the results of various methodological approaches applied to the DEMS led to several critical commentaries. An expert panel was subsequently set up by the Health Effects Institute to evaluate the DEMS results, together with a large study in the trucking industry. The panel concluded that both studies provided a useful basis for quantitative risk assessments (QRAs) of DE exposure. However, the results of both studies were non-definitive as the studies suffer from several methodological shortcomings. We conducted a critical review of the studies used by the International Agency for Research on Cancer (IARC) working group to evaluate the relationship between DE and lung cancer. The aim was to assess whether the available studies support the statement of a causal relationship and, secondarily if they could be used for QRA. Our review highlights several methodological flaws in the studies, amongst them overadjustment bias, selection bias, and confounding bias. The conclusion from our review is that the currently published studies provide little evidence for a definite causal link between DE exposure and lung cancer risk. Based on two studies in miners, the DEMS and the German Potash Miners study, QRA may be conducted. However, the DEMS data should be reanalyzed in advance to avoid bias that affects the presently published risk estimates.

Characterization of indoor diesel exhaust emissions from the parking garage of a school

Diesel exhaust (DE) emissions from a parking garage located in the basement of a school were characterized during spring and winter using direct reading devices and integrated sampling methods. Concentrations of CO and NO₂ were evaluated using electrochemical sensors and passive colorimetric tubes, respectively. Elemental and total carbon concentrations were measured using the NIOSH 5040 method. Particle number concentrations (PNCs), respirable particulate matter (PM_resp) mass concentrations, and size distributions were evaluated using direct reading devices. Indoor concentrations of elemental carbon, PNC, CO, and NO₂ showed significant seasonal variation; concentrations were much higher during winter (p < 0.01). Concentrations of the PM_resp and total carbon did not show significant seasonal variation. Pearson correlation coefficients were 0.9 (p < 0.01) and 0.94 (p < 0.01) between the parking garage and ground floor average daily PNCs, and between the parking garage and first floor average daily PNCs, respectively. Since DE is the main identified source of fine and ultrafine particles in the school, these results suggest that DE emissions migrate from the parking garage into the school. Our results highlight the relevance of direct reading instruments in identifying migration of contaminants and suggest that monitoring PNC is a more specific way of assessing exposure to DE than monitoring the common PM_resp fraction.

US long-haul truck driver health demands integrated approach

Purpose

The purpose of this paper is to provide a review of both occupational safety and health (OSH) and worksite health promotion (WHP) efforts targeted at long-haul truck drivers (LHTDs) and to identify strengths and weaknesses to inform future interventions and/or policy changes.

Design/methodology/approach

Review of the literature was done to identify theoretical and methodological approaches frequently used for protecting and promoting the health and well-being of LHTDs.

Findings

Health and safety issues impacting LHTDs are complex and naturally interrelated. Historically, the majority of approaches to the health and safety of LHTDs have emphasized the safety side and there has been a lack of comprehensive and integrated WHP/OSH attempts.

Originality/value

The literature pertaining to LHTD health has expanded in recent years, but intervention and policy efforts have had limited success. Several scholars have discussed the need for integrating WHP/OSH efforts for LHTD health, but have not actually provided a description or a framework of what it entails in which the authors provide a conclusion to the review of the literature. The authors provide a critical discussion regarding a collaborative approach focused on National Institute of Occupational Safety and Health’s Total Worker Health model. The integration further promotes an advancement of theoretical and methodological strategies.

Is diesel equipment in the workplace safe or not?

OBJECTIVES

Recently, diesel motor exhaust (DME) has been classified as a known human carcinogen. We used data from epidemiological studies of diesel exposures to perform a quantitative risk assessment to calculate DME exposure levels, expressed as elemental carbon (EC), corresponding to acceptable risk (AR) and maximum tolerable risk (MTR) levels of 4 to 10^-5 and 4 to 10^-3 for the lifetime excess probability of dying from lung cancer.

METHODS

Previously published slope estimates (n=14) of the exposure-response curve (ERC) for EC exposure and lung cancer were used in life-table analyses to calculate EC exposure levels corresponding to the specified AR and MTR levels.

RESULTS

Considered ERC slope factors ranged from 0.00060 to 0.0012 natural logarithm of the relative rate (InRR) per μg/m³ years based on different selections of studies and study-specific risk estimates. Exposure limits based on these slope factors were between 0.009-0.017 and 0.85-1.67 μg/m³ EC for the AR and MTR, respectively.

CONCLUSIONS

Derived exposure limits based on the AR and MTR are around or well below 1 μg/m³ EC. Such limits are below current occupational exposure levels, and in some instances even below environmental exposure levels. Although uncertainties exist in the exact slope factors, these results indicate that an acceptable excess lung cancer mortality risk can only be achieved at very low DME exposure levels, suggesting that diesel engines using older technologies should be removed from the workplace when possible or emissions strictly controlled.

Reducing the underreporting of lung cancer attributable to occupation: outcomes from a hospital-based systematic search in Northern Italy

PURPOSE

Occupational exposure to lung carcinogens is and was common in workplaces. 5-25 % of lung cancers (LCs) could be causally attributable to occupation; however, LC underreporting and undercompensation are widespread, with remarkable tolls paid by individuals and society. This work aims to: describe an ongoing hospital-based systematic search (SS) of occupational LC; improve aetiological diagnosis; increase number and quality of LC notifications.

METHODS

Through a short form, physicians at a public hospital referred incident LC to the Occupational Health Unit (OHU). Only patients selected through the form were interviewed; a personal, occupational and clinical history was collected; reports were sent to the ward and Local Health Authority, with aetiological diagnosis criteria and probability of causation.

RESULTS

From 1998 to 2013, 3274 cases of LC were notified to the OHU; prior to the system, just couple of dozens were assessed. A total of 1522 patients were fully interviewed; in 395 cases, causation was attributed to occupation (26 % of interviewed patients); all were notified to authorities, as compared to the handful reported before the system was adopted. Main aetiological agents were silica, asbestos, polycyclic aromatic hydrocarbons, truck driving, painting, multiple exposures. Compensation rate was remarkable (39 %).

CONCLUSIONS

Through SS, many occupational LCs were found that otherwise would have been lost. Aetiological diagnosis proved to be rich of scientific advantages and practical implications, with attention to equity and social aspects. SS was easy, accountable and fostered multidisciplinary collaboration among medical specialties, significantly reducing underreporting and undercompensation of occupational LC.

Evaluation of the reactivity of exhaust from various biodiesel blends as a measure of possible oxidative effects: A concern for human exposure

Diesel exhaust particles (DEP) are a major constituent of ambient air pollution and are associated with various adverse health effects, posing a major safety and public health concern in ambient and occupational environments. The effects of DEP from various biodiesel blends on biological systems was investigated using glutathione (GSH) as a marker of possible oxidative effects, based on the decrease in the concentration of GSH at physiological pH. The fluorophoric agent 2,3-naphthalenedicarboxaldehyde (NDA) was used as a selective probe of GSH in the presence of any likely interferents via fluorescence detection. Three different polar solvents (acetonitrile, methanol and water) were used to extract DEP generated during the combustion of different biodiesel blends (5%-99%). Oxidation of GSH to the disulfide (GSSG) was confirmed using electrospray ionization mass spectrometry. A decrease in the concentration of GSH was observed in the presence of DEP extracts from all of the biodiesel blends studied, with reaction rates that depend on the biodiesel blend. Interestingly the reactivity peaked at 50% biodiesel (B50) rather than decreasing monotonically with increased biodiesel content, as was expected. Organic solvent DEP extracts showed wider variations in reactivity with GSH, with methanol extracts giving the largest decrease in GSH concentrations. This may imply a more organic nature of the oxidants in the biodiesel exhaust. It is therefore important to consider ways of reducing concentrations of organic components in biodiesel exhaust that can cause different toxic activity before any blend is offered as a preferred alternative to petroleum diesel fuel.

Particulate matter air pollution components and risk for lung cancer

BACKGROUND

Particulate matter (PM) air pollution is a human lung carcinogen; however, the components responsible have not been identified. We assessed the associations between PM components and lung cancer incidence.

METHODS

We used data from 14 cohort studies in eight European countries. We geocoded baseline addresses and assessed air pollution with land-use regression models for eight elements (Cu, Fe, K, Ni, S, Si, V and Zn) in size fractions of PM2.5 and PM10. We used Cox regression models with adjustment for potential confounders for cohort-specific analyses and random effect models for meta-analysis.

RESULTS

The 245,782 cohort members contributed 3,229,220 person-years at risk. During follow-up (mean, 13.1 years), 1878 incident cases of lung cancer were diagnosed. In the meta-analyses, elevated hazard ratios (HRs) for lung cancer were associated with all elements except V; none was statistically significant. In analyses restricted to participants who did not change residence during follow-up, statistically significant associations were found for PM2.5 Cu (HR, 1.25; 95% CI, 1.01-1.53 per 5 ng/m(3)), PM10 Zn (1.28; 1.02-1.59 per 20 ng/m(3)), PM10 S (1.58; 1.03-2.44 per 200 ng/m(3)), PM10 Ni (1.59; 1.12-2.26 per 2 ng/m(3)) and PM10 K (1.17; 1.02-1.33 per 100 ng/m(3)). In two-pollutant models, associations between PM10 and PM2.5 and lung cancer were largely explained by PM2.5 S.

CONCLUSIONS

This study indicates that the association between PM in air pollution and lung cancer can be attributed to various PM components and sources. PM containing S and Ni might be particularly important.

Occupational Diesel Exposure, Duration of Employment, and Lung Cancer: An Application of the Parametric G-Formula

BACKGROUND

If less healthy workers terminate employment earlier, thus accumulating less exposure, yet remain at greater risk of the health outcome, estimated health effects of cumulative exposure will be biased downward. If exposure also affects termination of employment, then the bias cannot be addressed using conventional methods. We examined these conditions as a prelude to a reanalysis of lung cancer mortality in the Diesel Exhaust in Miners Study.

METHODS

We applied an accelerated failure time model to assess the effect of exposures to respirable elemental carbon (a surrogate for diesel) on time to termination of employment among nonmetal miners who ever worked underground (n = 8,307). We then applied the parametric g-formula to assess how possible interventions setting respirable elemental carbon exposure limits would have changed lifetime risk of lung cancer, adjusting for time-varying employment status.

RESULTS

Median time to termination was 36% shorter (95% confidence interval = 33%, 39%), per interquartile range width increase in respirable elemental carbon exposure. Lung cancer risk decreased with more stringent interventions, with a risk ratio of 0.8 (95% confidence interval = 0.5, 1.1) comparing a limit of ≤25 µg/m respirable elemental carbon to no intervention. The fraction of cases attributable to diesel exposure was 27% in this population.

CONCLUSIONS

The g-formula controlled for time-varying confounding by employment status, the signature of healthy worker survivor bias, which was also affected by diesel exposure. It also offers an alternative approach to risk assessment for estimating excess cumulative risk, and the impact of interventions based entirely on an observed population.

National Survey of US Long-Haul Truck Driver Health and Injury: health behaviors

OBJECTIVE

To compare selected health behaviors and body mass index (modifiable risk factors) of US long-haul truck drivers to the US working population by sex.

METHODS

The National Survey of US Long-Haul Truck Driver Health and Injury interviewed a nationally representative sample of long-haul truck drivers (n = 1265) at truck stops. Age-adjusted results were compared with national health surveys.

RESULTS

Compared with US workers, drivers had significantly higher body mass index, current cigarette use, and pack-years of smoking; lower prevalence of annual influenza vaccination; and generally lower alcohol consumption. Physical activity level was low for most drivers, and 25% had never had their cholesterol levels tested.

CONCLUSIONS

Working conditions common to long-haul trucking may create significant barriers to certain healthy behaviors; thus, transportation and health professionals should address the unique work environment when developing interventions for long-haul drivers.

Diesel engine exhaust and lung cancer risks - evaluation of the meta-analysis by Vermeulen et al. 2014

BACKGROUND

Vermeulen et al. 2014 published a meta-regression analysis of three relevant epidemiological US studies (Steenland et al. 1998, Garshick et al. 2012, Silverman et al. 2012) that estimated the association between occupational diesel engine exhaust (DEE) exposure and lung cancer mortality. The DEE exposure was measured as cumulative exposure to estimated respirable elemental carbon in μg/m(3)-years. Vermeulen et al. 2014 found a statistically significant dose-response association and described elevated lung cancer risks even at very low exposures.

METHODS

We performed an extended re-analysis using different modelling approaches (fixed and random effects regression analyses, Greenland/Longnecker method) and explored the impact of varying input data (modified coefficients of Garshick et al. 2012, results from Crump et al. 2015 replacing Silverman et al. 2012, modified analysis of Moehner et al. 2013).

RESULTS

We reproduced the individual and main meta-analytical results of Vermeulen et al. 2014. However, our analysis demonstrated a heterogeneity of the baseline relative risk levels between the three studies. This heterogeneity was reduced after the coefficients of Garshick et al. 2012 were modified while the dose coefficient dropped by an order of magnitude for this study and was far from being significant (P = 0.6). A (non-significant) threshold estimate for the cumulative DEE exposure was found at 150 μg/m(3)-years when extending the meta-analyses of the three studies by hockey-stick regression modelling (including the modified coefficients for Garshick et al. 2012). The data used by Vermeulen and colleagues led to the highest relative risk estimate across all sensitivity analyses performed. The lowest relative risk estimate was found after exclusion of the explorative study by Steenland et al. 1998 in a meta-regression analysis of Garshick et al. 2012 (modified), Silverman et al. 2012 (modified according to Crump et al. 2015) and Möhner et al. 2013. The meta-coefficient was estimated to be about 10-20 % of the main effect estimate in Vermeulen et al. 2014 in this analysis.

CONCLUSIONS

The findings of Vermeulen et al. 2014 should not be used without reservations in any risk assessments. This is particularly true for the low end of the exposure scale.

Reanalysis of the DEMS nested case-control study of lung cancer and diesel exhaust: suitability for quantitative risk assessment

The International Agency for Research on Cancer (IARC) in 2012 upgraded its hazard characterization of diesel engine exhaust (DEE) to "carcinogenic to humans." The Diesel Exhaust in Miners Study (DEMS) cohort and nested case-control studies of lung cancer mortality in eight U.S. nonmetal mines were influential in IARC's determination. We conducted a reanalysis of the DEMS case-control data to evaluate its suitability for quantitative risk assessment (QRA). Our reanalysis used conditional logistic regression and adjusted for cigarette smoking in a manner similar to the original DEMS analysis. However, we included additional estimates of DEE exposure and adjustment for radon exposure. In addition to applying three DEE exposure estimates developed by DEMS, we applied six alternative estimates. Without adjusting for radon, our results were similar to those in the original DEMS analysis: all but one of the nine DEE exposure estimates showed evidence of an association between DEE exposure and lung cancer mortality, with trend slopes differing only by about a factor of two. When exposure to radon was adjusted, the evidence for a DEE effect was greatly diminished, but was still present in some analyses that utilized the three original DEMS DEE exposure estimates. A DEE effect was not observed when the six alternative DEE exposure estimates were utilized and radon was adjusted. No consistent evidence of a DEE effect was found among miners who worked only underground. This article highlights some issues that should be addressed in any use of the DEMS data in developing a QRA for DEE.

Commentary: Flawed scientific-evidence standards delay diesel regulations

Of 188 government-monitored air toxics, diesel particulate matter (DPM) causes seven times more cancer than all the other 187 air toxics combined, including benzene, lead, and mercury. Yet, DPM is the only air toxic not regulated more stringently under the Clean Air Act, as a hazardous air pollutant (HAP). One reason is that regulators use flawed standards of scientific evidence. The article argues (1) that DPM meets all six specified evidentiary criteria, any one of which is sufficient for HAP regulation and (2) that regulators' standards of evidence for denying HAP status to DPM (no DPM unit-risk estimate, inadequate dose-response data, alleged weak mechanistic data) err logically and scientifically, set the evidence bar too high, delay regulation, and allow 21,000 avoidable DPM deaths annually in the U.S.

Are urinary PAHs biomarkers of controlled exposure to diesel exhaust?

Urinary polycyclic aromatic hydrocarbons (PAHs) were evaluated as possible biomarkers of exposure to diesel exhaust (DE) in two controlled-chamber studies. We report levels of 14 PAHs from 28 subjects in urine that were collected before, immediately after and the morning after exposure. Using linear mixed-effects models, we tested for effects of DE exposure and several covariates (time, age, gender and urinary creatinine) on urinary PAH levels. DE exposures did not significantly alter urinary PAH levels. We conclude that urinary PAHs are not promising biomarkers of short-term exposures to DE in the range of 106-276 µg/m(3).

Exposure-response estimates for diesel engine exhaust and lung cancer mortality based on data from three occupational cohorts

BACKGROUND

Diesel engine exhaust (DEE) has recently been classified as a known human carcinogen.

OBJECTIVE

We derived a meta-exposure-response curve (ERC) for DEE and lung cancer mortality and estimated lifetime excess risks (ELRs) of lung cancer mortality based on assumed occupational and environmental exposure scenarios.

METHODS

We conducted a meta-regression of lung cancer mortality and cumulative exposure to elemental carbon (EC), a proxy measure of DEE, based on relative risk (RR) estimates reported by three large occupational cohort studies (including two studies of workers in the trucking industry and one study of miners). Based on the derived risk function, we calculated ELRs for several lifetime occupational and environmental exposure scenarios and also calculated the fractions of annual lung cancer deaths attributable to DEE.

RESULTS

We estimated a lnRR of 0.00098 (95% CI: 0.00055, 0.0014) for lung cancer mortality with each 1-μg/m3-year increase in cumulative EC based on a linear meta-regression model. Corresponding lnRRs for the individual studies ranged from 0.00061 to 0.0012. Estimated numbers of excess lung cancer deaths through 80 years of age for lifetime occupational exposures of 1, 10, and 25 μg/m3 EC were 17, 200, and 689 per 10,000, respectively. For lifetime environmental exposure to 0.8 μg/m3 EC, we estimated 21 excess lung cancer deaths per 10,000. Based on broad assumptions regarding past occupational and environmental exposures, we estimated that approximately 6% of annual lung cancer deaths may be due to DEE exposure.

CONCLUSIONS

Combined data from three U.S. occupational cohort studies suggest that DEE at levels common in the workplace and in outdoor air appear to pose substantial excess lifetime risks of lung cancer, above the usually acceptable limits in the United States and Europe, which are generally set at 1/1,000 and 1/100,000 based on lifetime exposure for the occupational and general population, respectively.

Diesel and silica monitoring at two sites following hurricane sandy

Following Hurricane Sandy, which hit New York City and New Jersey in October 2012, industrial hygienists from the Mount Sinai and Belleview/New York University occupational medicine clinics conducted monitoring for diesel exhaust and silica in lower Manhattan and Rockaway Peninsula. Average daytime elemental carbon levels at three stations in lower Manhattan on December 4, 2012, ranged from 9 to18 μg/m(3). Sub-micron particle counts at various times on the same day were over 200,000 particles per cubic centimeter on many streets in lower Manhattan. In Rockaway Peninsula on December 12, 2012, all average daytime elemental carbon levels were below a detection limit of approximately 7 μg/m(3). The average daytime crystalline silica dust concentration was below detection at two sites on Rockaway Peninsula, and was 0.015 mg/m(3) quartz where sand was being replaced on the beach. The daily average levels of elemental carbon and airborne particulates that we measured are in the range of levels that have been found to cause respiratory effects in sensitive subpopulations like asthmatic patients after 2 hr of exposure. Control of exposure to diesel exhaust must be considered following natural disasters where diesel-powered equipment is used in cleanup and recovery. Although peak silica exposures were not likely captured in this study, but were reported by a government agency to have exceeded recommended guidelines for at least one cleanup worker, we recommend further study of silica exposures when debris removal operations or traffic create visible levels of suspended dust from soil or sand.

Environmental exposure to carcinogens in northwestern Cameroon

BACKGROUND

In developing countries, 6% of deaths are due to cancer but cancer prevention is not practiced. Humans can prevent themselves from a number of workplace and environmental carcinogens.

OBJECTIVES

To assess exposure to carcinogens, risky behaviours and associated preventive methods.

METHODS

A structured questionnaire was used to collect information on carcinogen exposure in the workplace and environment through trained field staff from volunteers after gaining informed consent. Data was analysed using SPSS.

RESULTS

Participants were exposed to recognized carcinogens and environmental hazards. Thirty-five (83.3%) [95% CI: 72.0- 94.6] participants knew the carcinogen names they were exposed to. Common hygienic practices such as taking a bath and washing work dresses at the workplace, use of detergents to wash hands, and no smoking or eating at the workplace were poor. Twenty-nine (69.0%) [95% CI: 47.0 - 75.0] participants could smell the carcinogenic chemicals they use. Thirty (71.4%) [95% CI: 65.0 - 77.0] participants had been instructed in the use of protective equipment against carcinogens. Participants used preventive devices like hand gloves, laboratory coats, boots, face masks, goggles, ear plugs and respirators.

CONCLUSIONS

Exposure to carcinogens is common necessitating case-control and cohort studies in this locality on cancer prevalence and incidence.

Lung cancer and elemental carbon exposure in trucking industry workers

BACKGROUND

Diesel exhaust has been considered to be a probable lung carcinogen based on studies of occupationally exposed workers. Efforts to define lung cancer risk in these studies have been limited in part by lack of quantitative exposure estimates.

OBJECTIVE

We conducted a retrospective cohort study to assess lung cancer mortality risk among U.S. trucking industry workers. Elemental carbon (EC) was used as a surrogate of exposure to engine exhaust from diesel vehicles, traffic, and loading dock operations.

METHODS

Work records were available for 31,135 male workers employed in the unionized U.S. trucking industry in 1985. A statistical model based on a national exposure assessment was used to estimate historical work-related exposures to EC. Lung cancer mortality was ascertained through the year 2000, and associations with cumulative and average EC were estimated using proportional hazards models.

RESULTS

Duration of employment was inversely associated with lung cancer risk consistent with a healthy worker survivor effect and a cohort composed of prevalent hires. After adjusting for employment duration, we noted a suggestion of a linear exposure-response relationship. For each 1,000-µg/m³ months of cumulative EC, based on a 5-year exposure lag, the hazard ratio (HR) was 1.07 [95% confidence interval (CI): 0.99, 1.15] with a similar association for a 10-year exposure lag [HR = 1.09 (95% CI: 0.99, 1.20)]. Average exposure was not associated with relative risk.

CONCLUSIONS

Lung cancer mortality in trucking industry workers increased in association with cumulative exposure to EC after adjusting for negative confounding by employment duration.

Lung cancer and diesel exhaust: an updated critical review of the occupational epidemiology literature

A recent review concluded that the evidence from epidemiology studies was indeterminate and that additional studies were required to support the diesel exhaust-lung cancer hypothesis. This updated review includes seven recent studies. Two population-based studies concluded that significant exposure-response (E-R) trends between cumulative diesel exhaust and lung cancer were unlikely to be entirely explained by bias or confounding. Those studies have quality data on life-style risk factors, but do not allow definitive conclusions because of inconsistent E-R trends, qualitative exposure estimates and exposure misclassification (insufficient latency based on job title), and selection bias from low participation rates. Non-definitive results are consistent with the larger body of population studies. An NCI/NIOSH cohort mortality and nested case-control study of non-metal miners have some surrogate-based quantitative diesel exposure estimates (including highest exposure measured as respirable elemental carbon (REC) in the workplace) and smoking histories. The authors concluded that diesel exhaust may cause lung cancer. Nonetheless, the results are non-definitive because the conclusions are based on E-R patterns where high exposures were deleted to achieve significant results, where a posteriori adjustments were made to augment results, and where inappropriate adjustments were made for the "negative confounding" effects of smoking even though current smoking was not associated with diesel exposure and therefore could not be a confounder. Three cohort studies of bus drivers and truck drivers are in effect air pollution studies without estimates of diesel exhaust exposure and so are not sufficient for assessing the lung cancer-diesel exhaust hypothesis. Results from all occupational cohort studies with quantitative estimates of exposure have limitations, including weak and inconsistent E-R associations that could be explained by bias, confounding or chance, exposure misclassification, and often inadequate latency. In sum, the weight of evidence is considered inadequate to confirm the diesel-lung cancer hypothesis.

Health effects research and regulation of diesel exhaust: an historical overview focused on lung cancer risk

The mutagenicity of organic solvent extracts from diesel exhaust particulate (DEP), first noted more than 55 years ago, initiated an avalanche of diesel exhaust (DE) health effects research that now totals more than 6000 published studies. Despite an extensive body of results, scientific debate continues regarding the nature of the lung cancer risk posed by inhalation of occupational and environmental DE, with much of the debate focused on DEP. Decades of scientific scrutiny and increasingly stringent regulation have resulted in major advances in diesel engine technologies. The changed particulate matter (PM) emissions in "New Technology Diesel Exhaust (NTDE)" from today's modern low-emission, advanced-technology on-road heavy-duty diesel engines now resemble the PM emissions in contemporary gasoline engine exhaust (GEE) and compressed natural gas engine exhaust more than those in the "traditional diesel exhaust" (TDE) characteristic of older diesel engines. Even with the continued publication of epidemiologic analyses of TDE-exposed populations, this database remains characterized by findings of small increased lung cancer risks and inconsistent evidence of exposure-response trends, both within occupational cohorts and across occupational groups considered to have markedly different exposures (e.g. truckers versus railroad shopworkers versus underground miners). The recently published National Institute for Occupational Safety and Health (NIOSH)-National Cancer Institute (NCI) epidemiologic studies of miners provide some of the strongest findings to date regarding a DE-lung cancer association, but some inconsistent exposure-response findings and possible effects of bias and exposure misclassification raise questions regarding their interpretation. Laboratory animal studies are negative for lung tumors in all species, except for rats under lifetime TDE-exposure conditions with durations and concentrations that lead to "lung overload." The species specificity of the rat lung response to overload, and its occurrence with other particle types, is now well-understood. It is thus generally accepted that the rat bioassay for inhaled particles under conditions of lung overload is not predictive of human lung cancer hazard. Overall, despite an abundance of epidemiologic and experimental data, there remain questions as to whether TDE exposure causes increased lung cancers in humans. An abundance of emissions characterization data, as well as preliminary toxicological data, support NTDE as being toxicologically distinct from TDE. Currently, neither epidemiologic data nor animal bioassay data yet exist that directly bear on NTDE carcinogenic potential. A chronic bioassay of NTDE currently in progress will provide data on whether NTDE poses a carcinogenic hazard, but based on the significant reductions in PM mass emissions and the major changes in PM composition, it has been hypothesized that NTDE has a low carcinogenic potential. When the International Agency for Research on Cancer (IARC) reevaluates DE (along with GEE and nitroarenes) in June 2012, it will be the first authoritative body to assess DE carcinogenic health hazards since the emergence of NTDE and the accumulation of data differentiating NTDE from TDE.

A retrospective assessment of occupational exposure to elemental carbon in the U.S. trucking industry

BACKGROUND

Despite considerable epidemiologic evidence about the health effects of chronic exposure to vehicle exhaust, efforts at defining the extent of risk have been limited by the lack of historical exposure measurements suitable for use in epidemiologic studies and for risk assessment.

OBJECTIVES

We sought to reconstruct exposure to elemental carbon (EC), a marker of diesel and other vehicle exhaust exposure, in a large national cohort of U.S. trucking industry workers.

METHODS

We identified the predictors of measured exposures based on a statistical model and used this information to extrapolate exposures across the cohort nationally. These estimates were adjusted for changes in work-related conditions over time based on a previous exposure assessment of this industry, and for changes in background levels based on a trend analysis of historical air pollution data, to derive monthly estimates of EC exposure for each job and trucking terminal combination between 1971 and 2000.

RESULTS

Occupational exposure to EC declined substantially over time, and we found significant variability in estimated exposures both within and across job groups, trucking terminals, and regions of the United States. Average estimated EC exposures during a typical work shift ranged from < 1 μg/m³ in the lowest exposed category in the 1990s to > 40 μg/m³ for workers in the highest exposed jobs in the 1970s.

CONCLUSIONS

Our results provide a framework for understanding changes over time in exposure to EC in the U.S. trucking industry. Our assessment should minimize exposure misclassification by capturing variation among terminals and across U.S. regions, and changes over time.

Occupational lung cancer in US women, 1984-1998

BACKGROUND

Lung cancer is the leading cause of cancer death in US women, accounting for 72,130 deaths in 2006. In addition to smoking cessation, further reduction of the burden of lung cancer mortality can be made by preventing exposure to occupational lung carcinogens. Data for occupational exposures and health outcomes of US working women are limited.

METHODS

Population-based mortality data for 4,570,711 women who died between 1984 and 1998 in 27 US States were used to evaluate lung cancer proportionate mortality over time by the usual occupation and industry reported on death certificates. Lung cancer proportionate mortality ratios were adjusted for smoking, using data from the National Health Interview Survey (NHIS) and the American Cancer Society's Cancer Prevention Study II.

RESULTS

Analyses revealed that 194,382 white, 18,225 Black and 1,515 Hispanic women died 1984-1998 with lung cancer reported as the underlying cause of death. Following adjustment for smoking, significant excess proportionate lung cancer mortality was observed among US women working in the US manufacturing; transportation; retail trade; agriculture, forestry, and fishing; and nursing/personal care industries. Women employed in precision production, technical, managerial, professional specialty, and administrative occupations experienced some of the highest significantly excess proportionate lung cancer mortality during 1984-1998.

CONCLUSIONS

The results of our study point to significantly elevated risks for lung cancer after adjustment for smoking among women in several occupations and industries. Because 6-17% of lung cancer in US males is attributable to known exposures to occupational carcinogens, and since synergistic interactions between cigarette smoke and other occupational lung carcinogens have been noted, it is important to continue research into the effects of occupational exposures on working men and women.

Mortality among Members of a Truck Driver Trade Association

Previous studies report that truck drivers are at increased risk for illness and on-the-job mortality. It is unknown whether owner-operator truck drivers face the same risks as employee drivers, yet few studies have targeted owner-operators as a study population. This study examined the overall and cause-specific mortality ratios for a cohort with owner-operator truck drivers constituting 69% of the study population. Of the 26 major disease classifications and 92 specific causes of death examined, only mortality due to transportation accidents was significantly elevated (standardized mortality ratio = 1.52, 95% confidence interval = 1.36–1.70). Leading causes of death were ischemic heart disease and lung cancer, although risk was below that of the general population. Transportation accidents pose a particular hazard for members of the trade association. The absence of excess disease mortality deserves careful interpretation, and may be due to both a strong healthy worker effect and a short monitoring period.

Worksite-induced morbidities among truck drivers in the United States

A critical review was conducted of social, psychological, and health science literature on the array of health risks and morbidities of truckers. Multilevel worksite-induced strains (e.g., long work hours and fatigue, shift work and sleep deprivation, postural fatigue and exposure to noise and vibration, sedentary lifestyle and unhealthy diet, exposure to diesel exhaust fumes, and other occupational stressors) were categorized into six primary morbidities for truckers: (1) psychological and psychiatric disorders; (2) detriments resulting from disrupted biological cycles; (3) musculoskeletal disorders; (4) cancer and respiratory morbidities; (5) cardiovascular disease; and (6) risk-laden substance use and sexual practices. Elevated morbidity risks suggest the need for the design and implementation of systematic epidemiological research and environmental interventions in the transport sector.