Methylated polycyclic aromatic hydrocarbons from household coal use across the life course and risk of lung cancer in a large cohort of 42,420 subjects in Xuanwei, China

BACKGROUND

We previously showed that exposure to 5-methylchrysene (5MC) and other methylated polycyclic aromatic hydrocarbons (PAHs) best explains lung cancer risks in a case-control study among non-smoking women using smoky coal in China. Time-related factors (e.g., age at exposure) and non-linear relations were not explored.

OBJECTIVE

We investigated the relation between coal-derived air pollutants and lung cancer mortality using data from a large retrospective cohort.

METHODS

Participants were smoky (bituminous) or smokeless (anthracite) coal users from a cohort of 42,420 subjects from four communes in XuanWei. Follow-up was from 1976 to 2011, during which 4,827 deaths from lung-cancer occurred. Exposures were predicted for 43 different pollutants. Exposure clusters were identified using hierarchical clustering. Cox regression was used to estimate exposure-response relations for 5MC, while effect modification by age at exposure was investigated for cluster prototypes. A Bayesian penalized multi-pollutant model was fitted on a nested case-control sample, with more restricted models fitted to investigate non-linear exposure-response relations.

RESULTS

We confirmed the strong exposure-response relation for 5MC (Hazard Ratio [95% Confidence Interval] = 2.5 [2.4, 2.6] per standard-deviation (SD)). We identified four pollutant clusters, with all but two PAHs in a single cluster. Exposure to PAHs in the large cluster was associated with a higher lung cancer mortality rate (HR [95%CI] = 2.4 [2.2, 2.6] per SD), while exposure accrued before 18 years of age appeared more important than adulthood exposures. Results from the multi-pollutant model identified anthanthrene (ANT) and benzo(a)chrysene (BaC) as risk factors. 5MC remained strongly associated with lung cancer in models that included ANT and BaC and also benzo(a)pyrene (BaP).

CONCLUSION

We confirmed the link between PAH exposures and lung cancer in smoky coal users and found exposures before age 18 to be especially important. We found some evidence for the carcinogen 5MC and non-carcinogens ANT and BaC.

Overall and cause-specific mortality rates among men and women with high exposure to indoor air pollution from the use of smoky and smokeless coal: a cohort study in Xuanwei, China

OBJECTIVES

Never-smoking women in Xuanwei (XW), China, have some of the highest lung cancer rates in the country. This has been attributed to the combustion of smoky coal used for indoor cooking and heating. The aim of this study was to evaluate the spectrum of cause-specific mortality in this unique population, including among those who use smokeless coal, considered 'cleaner' coal in XW, as this has not been well-characterised.

DESIGN

Cohort study.

SETTING

XW, a rural region of China where residents routinely burn coal for indoor cooking and heating.

PARTICIPANTS

Age-adjusted, cause-specific mortality rates between 1976 and 2011 were calculated and compared among lifetime smoky and smokeless coal users in a cohort of 42 420 men and women from XW. Mortality rates for XW women were compared with those for a cohort of predominately never-smoking women in Shanghai.

RESULTS

Mortality in smoky coal users was driven by cancer (41%), with lung cancer accounting for 88% of cancer deaths. In contrast, cardiovascular disease (CVD) accounted for 32% of deaths among smokeless coal users, with 7% of deaths from cancer. Total cancer mortality was four times higher among smoky coal users relative to smokeless coal users, particularly for lung cancer (standardised rate ratio (SRR)=17.6). Smokeless coal users had higher mortality rates of CVD (SRR=2.9) and pneumonia (SRR=2.5) compared with smoky coal users. These patterns were similar in men and women, even though XW women rarely smoked cigarettes. Women in XW, regardless of coal type used, had over a threefold higher rate of overall mortality, and most cause-specific outcomes were elevated compared with women in Shanghai.

CONCLUSIONS

Cause-specific mortality burden differs in XW based on the lifetime use of different coal types. These observations provide evidence that eliminating all coal use for indoor cooking and heating is an important next step in improving public health particularly in developing countries.

Association between diesel exhaust exposure and mitochondrial DNA methylation

BACKGROUND

Diesel exhaust is an established human carcinogen, however the mechanisms by which it leads to cancer development are not fully understood. Mitochondrial dysfunction is an established contributor to carcinogenesis. Recent studies have improved our understanding of the role played by epigenetic modifications in the mitochondrial genome on tumorigenesis. In this study, we aim to evaluate the association between diesel engine exhaust (DEE) exposure with mitochondrial DNA (mtDNA) methylation levels in workers exposed to DEE.

METHODS

The study population consisted of 53 male workers employed at a diesel engine manufacturing facility in Northern China who were routinely exposed to diesel exhaust in their occupational setting, as well as 55 unexposed male control workers from other unrelated factories in the same geographic area. Exposure to DEE, elemental carbon, organic carbon, and particulate matter (PM2.5) were assessed. mtDNA methylation for CpG sites (CpGs) from seven mitochondrial genes (D-Loop, MT-RNR1, MT-CO2, MT-CO3, MT-ATP6, MT-ATP8, MT-ND5) was measured in blood samples. Linear regression models were used to estimate the associations between DEE, elemental carbon, organic carbon and PM2.5 exposures with mtDNA methylation levels, adjusting for potential confounders.

RESULTS

DEE exposure was associated with decreased MT-ATP6 (difference= -35.6%, p-value= 0.019) and MT-ATP8 methylation (difference= -30%, p-value= 0.029) compared to unexposed controls. Exposures to elemental carbon, organic carbon, and PM2.5 were also significantly and inversely associated with methylation in MT-ATP6 and MT-ATP8 genes (all p-values < 0.05).

CONCLUSIONS

Our findings suggest that DEE exposure perturbs mtDNA methylation, which may be of importance for tumorigenesis.

Exposure to diesel engine exhaust and alterations to the Cys34/Lys525 adductome of human serum albumin

We investigated whether exposure to carcinogenic diesel engine exhaust (DEE) was associated with altered adduct levels in human serum albumin (HSA) residues. Nano-liquid chromatography-high resolution mass spectrometry (nLC-HRMS) was used to measure adducts of Cys34 and Lys525 residues in plasma samples from 54 diesel engine factory workers and 55 unexposed controls. An untargeted adductomics and bioinformatics pipeline was used to find signatures of Cys34/Lys525 adductome modifications. To identify adducts that were altered between DEE-exposed and unexposed participants, we used an ensemble feature selection approach that ranks and combines findings from linear regression and penalized logistic regression, then aggregates the important findings with those determined by random forest. We detected 40 Cys34 and 9 Lys525 adducts. Among these findings, we found evidence that 6 Cys34 adducts were altered between DEE-exposed and unexposed participants (i.e., 841.75, 851.76, 856.10, 860.77, 870.43, and 913.45). These adducts were biologically related to antioxidant activity.

The establishment of the Household Air Pollution Consortium (HAPCO)

Household air pollution (HAP) is of public health concern with ~3 billion people worldwide (including >15 million in the US) exposed. HAP from coal use is a human lung carcinogen, yet the epidemiological evidence on carcinogenicity of HAP from biomass use, primarily wood, is not conclusive. To robustly assess biomass's carcinogenic potential, prospective studies of individuals experiencing a variety of HAP exposures are needed. We have built a global consortium of 13 prospective cohorts (HAPCO: Household Air Pollution Consortium) that have site- and disease-specific mortality and solid fuel use data, for a combined sample size of 587,257 participants and 57,483 deaths. HAPCO provides a novel opportunity to assess the association of HAP with lung cancer death while controlling for important confounders such as tobacco and outdoor air pollution exposures. HAPCO is also uniquely positioned to determine the risks associated with cancers other than lung as well as non-malignant respiratory and cardiometabolic outcomes, for which prospective epidemiologic research is limited. HAPCO will facilitate research to address public health concerns associated with HAP-attributed exposures by enabling investigators to evaluate sex-specific and smoking status-specific effects under various exposure scenarios.

Abstract 3239: Molecular biomarkers and indoor household air pollution in a rural area of China

To explore the influence of fuel source used for home heating and cooking on biomarkers of potential genomic instability, we analyzed biological samples obtained from a cross-sectional study of 104 female never-smokers enrolled from 30 villages in Xuanwei and Fuyuan in Yunnan Province, a rural region with a high incidence of lung cancer in China. Study subjects who used primarily smoky (i.e., bituminous) coal (n=80), smokeless coal (i.e., anthracite) (n=14) and wood (n=10) were analyzed. Personal 24-h air PM2.5 and polycyclic aromatic hydrocarbon concentrations were measured over two consecutive days in each household. DNA was extracted from peripheral white blood cells. We assayed molecular biomarkers of potential genomic instability including the Alu copy number to albumin gene (ALB) ratio (Alu/ALB), 5.8S ribosomal DNA to ALB ratio (5.8S rDNA/ALB) and 18S ribosomal DNA to ALB ratio (18S rDNA/ALB), which were weakly to highly correlated with each other. Multiple linear regression was performed to analyze the association between fuel type and these biomarkers, adjusted for age, as well as the influence of benzo[a]pyrene (BaP) and PM2.5 concentration. There was a significant difference (p = 0.041) in levels of 18S rDNA/ALB among the three exposure groups [mean (standard deviation [sd]) = 1.30 (0.42), 1.58 (0.72), and 1.65 (0.62) among smoky, smokeless coal and wood users, respectively]. There were substantial differences in personal PM2.5 exposure among smoky coal, smokeless coal, and wood users [mean (sd) =184 (127), 227 (318), and 433 (284) µg/m3, respectively, p = 0.0004]. PM2.5 exposure was significantly and positively associated with 18S rDNA/ALB (p = 0.001). Further, after adjustment for PM2.5, the association between fuel type and 18S rDNA/ALB became non-significant (p = 0.24). Similar positive associations were observed between PM2.5 and 5.8S rDNA/ALB (p=0.009) and Alu/ALB (p=0.0003). There were no associations identified between BaP and these biomarkers after adjustment for PM2.5. Our findings suggest that exposure to PM2.5, which has been associated with increased risks of lung cancer and cardiovascular disease, may alter potential molecular markers of genomic instability. Additional studies are needed to confirm these findings and further understand the role of these biomarkers in predicting human health effects.

Citation Format: Wei Hu, Richard M. Cawthon, George Downward, Boris Reiss, Jihua Li, Jun He, Jun Xu, Wei Jie Seow, Bryan A. Bassig, Jason Y. Wong, Dean Hosgood, Lützen Portengen, Nathaniel Rothman, Roel Vermeulen, Qing Lan. Molecular biomarkers and indoor household air pollution in a rural area of China [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3239.

Abstract 3432: Outdoor air pollution and household coal combustion in a rural high lung cancer incidence area of China

Outdoor air pollution inside populated areas is a growing environmental health concern. Epidemiological data related to exposures to outdoor air pollution are limited in rural areas. We previously assessed indoor and personal exposures in two Chinese rural counties, Xuanwei and Fuyuan, where the domestic combustion of locally sourced “smoky” (i.e., bituminous) but not “smokeless” (i.e., anthracite) coal has been associated with the highest lung cancer rates in China. In addition, we have previously reported that improving home ventilation by installing stoves with chimneys was associated with a reduction in lung cancer rates in this region. However, outdoor air pollution from indoor burning of coal and the impact of improving household ventilation on outdoor air pollution have never been assessed in this area. Therefore, we measured outdoor fine particulate matter (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) including the known carcinogen benzo-a-pyrene (BaP) over two consecutive 24-hour sampling periods in 29 villages. Half of the villages were revisited several months after the initial sampling period to repeat all measurements. The overall concentrations of outdoor pollutants in Xuanwei and Fuyuan were 53.1 μg/m3 (13.2-103.4 μg/m3) for PM2.5, and 11.1 ng/m3 (5.9-19.8 ng/m3) for BaP. PM2.5 levels were almost twice as high as the 24-hour mean World Health Organization guideline value of 25 μg/m3. Outdoor BaP concentrations in villages with homes using smoky coal were significantly higher than those with homes that used smokeless coal (11.6 vs 5.9 ng/m3, p &lt; 0.05). Among villages using smoky coal, higher outdoor BaP levels were found in villages where &gt;50% of households had a chimney compared to villages where ≤50% of homes had a chimney (12.3 vs 7.1 ng/m3, p = 0.024). Outdoor PM2.5 was moderately correlated with the indoor concentration (Spearman rs = 0.28, p = 0.011). These results show that outdoor air pollution in a rural region of China with a high incidence of lung cancer was associated with type of coal used for cooking and heating indoors and the presence of stove ventilation. These findings suggest that further reducing adverse health effects in rural villages from home burning of coal will likely require use of stoves that reduce environmental exhaust and/or the replacement of coal with cleaner fuel types.

Citation Format: Wei Hu, George Downward, Boris Reiss, Nathaniel Rothman, Jihua Li, Jun He, K.F Morales-Collins, Jun Xu, Weijie Seow, Bryan Bassig, Dean Hosgood, Linlin Zhang, M Hoogeveen, Ingrid Rijk, Guoping Wu, Fusheng Wei, Roel Vermeulen, Qing Lan. Outdoor air pollution and household coal combustion in a rural high lung cancer incidence area of China. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3432.

Abstract 3428: Domestic livestock exposure and lung cancer risk among non-smoking women in Xuanwei, China

Background: Lung cancer rates of women in Xuanwei and Fuyuan, rural counties located in the Yunnan Province, are among the highest in China, even though most women there are non-smokers. The unusually high lung cancer rates are mainly attributed to smoky (i.e. bituminous) coal exposures. Many households there and in other rural parts of China have raised animals such as pigs, cows, horses, chickens and ducks in close proximity to their homes. It is hypothesized that contact with animals increases the risk of infection with potentially carcinogenic pathogens. However, findings on the association between livestock and poultry exposures and lung cancer risk, mostly from occupational studies, have been inconsistent.

Objective: To investigate the association between livestock and poultry exposures and lung cancer risk in a general population of non-smoking women who lived in close proximity to livestock and poultry in a rural area in China.

Methods: A hospital-based case-control study among non-smoking women was conducted in Xuanwei and Fuyuan counties in China between March 2006 and July 2013. A total of 1,074 lung cancer cases and 977 hospital-based cancer-free controls were enrolled. Exposure to livestock and poultry, including the animal type (pigs, cows/horses, chickens, ducks) and total number of years an individual was exposed to each animal type, was obtained by questionnaire. Reference groups for the analysis were either never-exposed, or never-exposed combined with those with less than the median years of exposure, depending on the prevalence of exposure to each animal. Logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of the association between livestock and poultry exposures and lung cancer risk with adjustment for potential confounders, such as lifetime amount of smoky coal used and passive smoking.

Results: Individuals with above the median number of years of exposure to pigs (OR = 1.61, 95% CI = 1.19-2.17) and chickens (OR = 1.49, 95% CI = 1.12-1.99) had increased lung cancer risk, compared to those who had less than the median years of exposure. Compared to those who were never exposed, the risk of lung cancer increased with longer duration of exposure to cows/horses (&lt;median years of exposure: OR = 1.33, 95% CI = 1.00-1.77; ≥median years of exposure: OR = 1.38, 95% CI = 1.03-1.86). The significant associations for pigs and cows/horses persisted after adjusting for other animal exposures in the same model.

Conclusions: Exposure to certain animals was significantly associated with increased lung cancer risk, suggesting that infectious agents may play a role in the etiology of lung cancer among non-smoking women in this region. However, due to the fact that this study was conducted in an area with a high risk of lung cancer due to the use of solid fuels for heating and cooking, we cannot rule out residual confounding.

Citation Format: Wei Jie Seow, Wei Hu, Roel Vermeulen, George Downward, Jihua Li, Jun Xu, Jun He, Fusheng Wei, Guoping Wu, Nathaniel Rothman, Robert S. Chapman, Qing Lan. Domestic livestock exposure and lung cancer risk among non-smoking women in Xuanwei, China. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3428.

Abstract 112: Transcriptomic changes in the oral mucosal epithelium reflect the physiologic response to indoor burning of solid fuels

RATIONALE: Human exposure to indoor smoke emissions from the domestic burning of solid fuels (e.g. coal, wood, plant materials) is a major cause of morbidity and mortality that affects nearly half of the world's population. While epidemiologic studies on the health impact of indoor air pollution (IAP) have yielded valuable insights from the use of various exposure assessments (e.g. personal and area air sampling, urinary metabolites), there is a need to connect these exposure measures to biomarkers of the host's physiologic response to exposure. We have previously shown that gene-expression (GE) profiles in the upper airway epithelium are affected by tobacco smoke. Thus, we sought to determine whether transcriptomic changes in the oral mucosal epithelium might also capture physiologic responses to IAP from the burning of solid fuels. METHODS: Buccal mucosa epithelial cell scrapings were collected from healthy, non-smoking female subjects in rural Xuanwei, China, where female lung cancer rates are among the highest in the world. Benzo(a)pyrene (BaP) exposure levels from indoor burning of solid fuels (primarily coal) for cooking and heating were measured by personal in-home air monitoring. RNA from 18 samples was extracted and processed onto Affymetrix Gene 1.0 ST arrays. Student's t-test and DAVID were used to identify and characterize genes that vary between relatively high levels of BaP exposure (n=8; BaP 99.0 +/- 45.9) and low (n=10; BaP 16.2 +/- 6.1) exposure. Using GSEA, results were compared to independent airway epithelial GE profiles that distinguish current smokers from never smokers and bronchial GE profiles in subjects with and without lung cancer. RESULTS: We identified 227 genes that were differentially expressed between subjects with high and low BaP exposure (p&lt;0.01). Genes elevated with high BaP exposure were enriched for genes involved in the activation of apoptosis and the Toll-Like Receptor Signaling pathway. Genes that we have previously shown to have altered expression in the bronchial, buccal, and nasal epithelium of current smokers relative to never smokers were enriched among the genes associated with BaP exposure (GSEA; q&lt;0.01). There was also a significant enrichment for bronchial epithelial airway genes that were altered in subjects with and without lung cancer in a previous report (GSEA; q&lt;0.01). CONCLUSION: Buccal epithelial GE is affected by BaP exposure in a population that uses coal and other solid fuels for indoor cooking and heating among healthy women in Xuanwei, China. Solid fuel emissions may elicit some of the same transcriptomic responses as cigarette smoke and lung cancer. This demonstrates the feasibility of using non-invasively collected buccal GE profiling to assess physiologic responses to other inhaled toxins such as coal smoke in population-based studies.

Citation Format: Teresa W. Wang, Qing Lan, Bozena Krystyna, Nathaniel Rothman, Roberta Florido, Wei Hu, Katrina Steiling, Gang Liu, Ji Xiao, Yuriy Alekseyev, Jun Xu, Fusheng Wei, H. Dean Hosgood, Boris Reiss, George Downward, Marc Lenburg, Roel Vermeulen, Avrum Spira. Transcriptomic changes in the oral mucosal epithelium reflect the physiologic response to indoor burning of solid fuels. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 112. doi:10.1158/1538-7445.AM2013-112

Human serum albumin induced hypotension in the postoperative phase of cardiac surgery

Hypotension associated with the rapid infusion of human serum albumin products was first recognised in Australasia in the early 1970s. An association with the angiotensin converting enzyme inhibitor class of drugs (ACE-I) followed, leading to a proposed mechanism involving bradykinin generation through pre-kallikrein activator (PKA) presence in the infused fluid. The newer generation albumin products (Albumex) contain very low concentrations of PKA and are generally thought safe to use in most patient populations. Anecdotal reports of paradoxical hypotension with rapid infusion of 4% albumin in our department led to an audit of practice over three months. Four out of 36 patients (11%) who received 4% albumin intravenously experienced paradoxical hypotension. Three of these patients were taking ACE-I preoperatively (P=0.04). There was no observed hypotension associated with intravenous infusion of crystalloid fluid. We believe 4% albumin should be used with caution, particularly in those patients receiving ACE-I preoperatively.

Evaluation of a new design of tracheal tube cuff to prevent leakage of fluid to the lungs

A new design of tracheal tube cuff was compared with two types of high-volume, low-pressure (HVLP) cuffed tracheal tube for leakage of fluid from the subglottic space into the trachea. Spontaneous and positive-pressure ventilation were simulated using a mechanical lung, an intubated model trachea and a ventilator. Excised human tracheas were intubated and leakage past the cuff assessed. Distention of the tracheal wall was measured. HVLP cuffs leaked rapidly in the model during all modes of ventilation, and also in the excised human tracheas. This leakage occurred preferentially down longitudinal folds that occur in the HVLP cuff wall. The new design completely prevented leakage in the model during all modes of ventilation, during tracheal suctioning, and with tube movement. The new cuff also prevented leakage in the excised human tracheas. Tracheal wall distention and tracheal wall pressures were similar for all cuffs tested.

Leakage of fluid past the tracheal tube cuff in a benchtop model

We have assessed a range of high volume, low pressure (HVLP) cuffed tracheal tubes in a benchtop model, for leakage of fluid from above the cuff to the model trachea below, during various ventilatory modes. Rapid leakage occurred in the model during all modes of ventilation, unless tracheal pressure was greater than the height of fluid in the column above the cuff. This leakage occurred preferentially down longitudinal folds that occur in the HVLP cuff wall. This model suggests that, if a longitudinal fold within the cuff wall is patent, then the possibility exists of subglottic to tracheal leakage.

Severe acute laryngotracheitis in Christchurch 1980-90

A review of children admitted to Christchurch Hospital with acute laryngotracheitis over a 10 year and nine month period revealed that 894 admissions occurred for this condition. Forty-four (4.9%) were admitted to the intensive care unit of the hospital, of whom 12 (1.3% of all laryngotracheitis admissions) required endotracheal intubation. The mean time of intubation was 170 hours (range 24-432). There were no deaths, although seven children who were intubated had serious complications, of which perforation of a gastric ulcer was the most important. In our group of patients intubation is a rare event, and the need for aggressive treatment with dexamethasone at the time of admission to the general ward is questioned.

Children admitted to a general intensive care unit

A retrospective analysis of the pattern of admission of children to the general intensive care unit of Christchurch Hospital during the period 1980-7 inclusive, is reported. Three hundred and ninety-nine children were admitted during this period and they formed 10.7% of all admissions to the unit. In addition to the intensive care specialist, a paediatrician was involved with the management on 260 occasions and a surgeon on 139 occasions. Acute epiglottitis was the single commonest medical cause for admission and trauma from motor vehicle accidents the commonest surgical reason. Overall mortality was 14.5%, 13% for medical conditions and 16% for those with surgical problems. These results are in keeping with those reported from overseas.