Carcinogenicity of household solid fuel combustion and of high-temperature frying

Indoor air pollution from solid fuels and peripheral blood DNA methylation: findings from a population study in Warsaw, Poland

DNA methylation is a potential mechanism linking indoor air pollution to adverse health effects. Fetal and early-life environmental exposures have been associated with altered DNA methylation and play a critical role in progress of diseases in adulthood. We investigated whether exposure to indoor air pollution from solid fuels at different lifetime periods was associated with global DNA methylation and methylation at the IFG2/H19 imprinting control region (ICR) in a population-based sample of non-smoking women from Warsaw, Poland. Global methylation and IFG2/H19 ICR methylation were assessed in peripheral blood DNA from 42 non-smoking women with Luminometric Methylation Assay (LUMA) and quantitative pyrosequencing, respectively. Linear regression models were applied to estimate associations between indoor air pollution and DNA methylation in the blood. Compared to women without exposure, the levels of LUMA methylation for women who had ever exposed to both coal and wood were reduced 6.70% (95% CI: -13.36, -0.04). Using both coal and wood before age 20 was associated with 6.95% decreased LUMA methylation (95% CI: -13.79, -0.11). Further, the negative correlations were more significant with exposure to solid fuels for cooking before age 20. There were no clear associations between indoor solid fuels exposure before age 20 and through the lifetime and IFG2/H19 ICR methylation. Our study of non-smoking women supports the hypothesis that exposure to indoor air pollution from solid fuels, even early-life exposure, has the capacity to modify DNA methylation that can be detected in peripheral blood.

Respiratory risks from household air pollution in low and middle income countries

A third of the world's population uses solid fuel derived from plant material (biomass) or coal for cooking, heating, or lighting. These fuels are smoky, often used in an open fire or simple stove with incomplete combustion, and result in a large amount of household air pollution when smoke is poorly vented. Air pollution is the biggest environmental cause of death worldwide, with household air pollution accounting for about 3·5-4 million deaths every year. Women and children living in severe poverty have the greatest exposures to household air pollution. In this Commission, we review evidence for the association between household air pollution and respiratory infections, respiratory tract cancers, and chronic lung diseases. Respiratory infections (comprising both upper and lower respiratory tract infections with viruses, bacteria, and mycobacteria) have all been associated with exposure to household air pollution. Respiratory tract cancers, including both nasopharyngeal cancer and lung cancer, are strongly associated with pollution from coal burning and further data are needed about other solid fuels. Chronic lung diseases, including chronic obstructive pulmonary disease and bronchiectasis in women, are associated with solid fuel use for cooking, and the damaging effects of exposure to household air pollution in early life on lung development are yet to be fully described. We also review appropriate ways to measure exposure to household air pollution, as well as study design issues and potential effective interventions to prevent these disease burdens. Measurement of household air pollution needs individual, rather than fixed in place, monitoring because exposure varies by age, gender, location, and household role. Women and children are particularly susceptible to the toxic effects of pollution and are exposed to the highest concentrations. Interventions should target these high-risk groups and be of sufficient quality to make the air clean. To make clean energy available to all people is the long-term goal, with an intermediate solution being to make available energy that is clean enough to have a health impact.

Increased oxidative DNA damage and decreased expression of base excision repair proteins in airway epithelial cells of women who cook with biomass fuels

To investigate whether biomass burning causes oxidative DNA damage and alters the expression of DNA base excision repair (BER) proteins in airway cells, sputum samples were collected from 80 premenopausal rural biomass-users and 70 age-matched control women who cooked with liquefied petroleum gas. Compared with control the airway cells of biomass-users showed increased DNA damage in alkaline comet assay. Biomass-users showed higher percentage of cells expressing oxidative DNA damage marker 8-oxoguanine and lower percentages of BER proteins OGG1 and APE1 by immunocytochemical staining. Reactive oxygen species (ROS) generation was doubled and level of superoxide dismutase was depleted significantly among biomass-users. The concentrations of particulate matters were higher in biomass-using households which positively correlated with ROS generation and negatively with BER proteins expressions. ROS generation was positively correlated with 8-oxoguanine and negatively with BER proteins suggesting cooking with biomass is a risk for genotoxicity among rural women in their child-bearing age.

Estimating the number of low-income americans exposed to household air pollution from burning solid fuels

BACKGROUND

Exposure to household air pollution (HAP) from inefficient biomass and coal stoves kills nearly 4 million people every year worldwide. HAP is an environmental risk associated with poverty that affects an estimated 3 billion people mostly in low- and middle-income countries.

OBJECTIVES

Our goal was to estimate the number of low-income Americans exposed to potentially health-damaging concentrations of HAP.

METHODS

We mapped county-level data for the percentage of households using wood, coal, and/or coke as their primary heating fuel along with percent of the population below the federal poverty level. Using U.S. Census data and the likelihood of fugitive emissions as reported in the literature, we estimated the number of low-income Americans potentially exposed to HAP.

RESULTS

Solid fuel is the primary heating source for > 2.5 million U.S. households, or 6.5 million people. The mapping exercise showed several rural areas, primarily in the northern and western regions, that have high levels of solid-fuel use and poverty. We then identified 117 counties with high co-incident poverty and solid-fuel use as high-priority counties for research into potential health risks from HAP. We estimate that between 500,000 and 600,000 low-income people in the United States are likely exposed to HAP from burning solid fuels within their homes.

CONCLUSION

HAP occurs within the United States and should be further investigated for adverse health risks, especially among those living in areas with rural poverty.

Esophageal Cancer, the Topmost Cancer at MTRH in the Rift Valley, Kenya, and Its Potential Risk Factors

Esophageal cancer at Moi Teaching and Referral Hospital (MTRH) is the leading cancer in men with a poor prognosis. A case control study (n = 159) aimed at the histology type, gender, and risk indicators was carried out at MTRH. Mantel Haenszel chi-square and logistic regression were employed for analysis. Squamous-cell carcinoma was the common histological type occurring in the middle third portion of the oesophagus. The occurrence of the cancer in males was 1.4 times that of females. The mean age was 56.1 yrs. Low socioeconomic, smoking, snuff use, alcohol, tooth loss, cooking with charcoal and firewood, hot beverage, and use of mursik were independently associated with esophageal cancer (P < 0.05). Using logistic regression adjusted for various factors, alcohol consumption was associated with the increased risk of esophageal cancer. AHR was 0.45 and 95% CI: 0.205-0.985, P = 0.046. A societal component of low socioeconomic conditions, a lifestyle component with specific practices such as the consumption of mursik, chang'aa, busaa, snuff, smoking, hot tea, poor oral hygiene, and an environmental component with potential exposure to high levels of nitrosamines, passive smoking, and cooking with coal, could be involved. The increase in experts at MTRH capable of diagnosing could be responsible for the increase in reporting this neoplasm.

Driver mutations among never smoking female lung cancer tissues in China identify unique EGFR and KRAS mutation pattern associated with household coal burning

Lung cancer in never smokers, which has been partially attributed to household solid fuel use (i.e., coal), is etiologically and clinically different from lung cancer attributed to tobacco smoking. To explore the spectrum of driver mutations among lung cancer tissues from never smokers, specifically in a population where high lung cancer rates have been attributed to indoor air pollution from domestic coal use, multiplexed assays were used to detect >40 point mutations, insertions, and deletions (EGFR, KRAS, BRAF, HER2, NRAS, PIK3CA, MEK1, AKT1, and PTEN) among the lung tumors of confirmed never smoking females from Xuanwei, China [32 adenocarcinomas (ADCs), 7 squamous cell carcinomas (SCCs), 1 adenosquamous carcinoma (ADSC)]. EGFR mutations were detected in 35% of tumors. 46% of these involved EGFR exon 18 G719X, while 14% were exon 21 L858R mutations. KRAS mutations, all of which were G12C_34G>T, were observed in 15% of tumors. EGFR and KRAS mutations were mutually exclusive, and no mutations were observed in the other tested genes. Most point mutations were transversions and were also found in tumors from patients who used coal in their homes. Our high mutation frequencies in EGFR exon 18 and KRAS and low mutation frequency in EGFR exon 21 are strikingly divergent from those in other smoking and never smoking populations from Asia. Given that our subjects live in a region where coal is typically burned indoors, our findings provide new insights into the pathogenesis of lung cancer among never smoking females exposed to indoor air pollution from coal.

Population cancer risks associated with coal mining: a systematic review

Background

Coal is produced across 25 states and provides 42% of US energy. With production expected to increase 7.6% by 2035, proximate populations remain at risk of exposure to carcinogenic coal products such as silica dust and organic compounds. It is unclear if population exposure is associated with increased risk, or even which cancers have been studied in this regard.

Methods

We performed a systematic review of English-language manuscripts published since 1980 to determine if coal mining exposure was associated with increased cancer risk (incidence and mortality).

Results

Of 34 studies identified, 27 studied coal mining as an occupational exposure (coal miner cohort or as a retrospective risk factor) but only seven explored health effects in surrounding populations. Overall, risk assessments were reported for 20 cancer site categories, but their results and frequency varied considerably. Incidence and mortality risk assessments were: negative (no increase) for 12 sites; positive for 1 site; and discordant for 7 sites (e.g. lung, gastric). However, 10 sites had only a single study reporting incidence risk (4 sites had none), and 11 sites had only a single study reporting mortality risk (2 sites had none). The ecological study data were particularly meager, reporting assessments for only 9 sites. While mortality assessments were reported for each, 6 had only a single report and only 2 sites had reported incidence assessments.

Conclusions

The reported assessments are too meager, and at times contradictory, to make definitive conclusions about population cancer risk due to coal mining. However, the preponderance of this and other data support many of Hill’s criteria for causation. The paucity of data regarding population exposure and risk, the widespread geographical extent of coal mining activity, and the continuing importance of coal for US energy, warrant further studies of population exposure and risk.

History of lung disease and risk of lung cancer in a population with high household fuel combustion exposures in rural China

History of chronic lung diseases and household coal use for heating and cooking are established risk factors of lung cancer; however, few studies have been able to explore these risk factors simultaneously. Xuanwei, China, has some of the highest rates of lung cancer in China and most residents experience substantial in-home coal smoke exposures. Using a population-based case-control study of 498 lung cancer cases and 498 age-matched controls, we evaluated the risk of lung cancer in relation to coal smoke exposure and history of chronic lung diseases, including chronic obstructive pulmonary disease (COPD), asthma, tuberculosis (TB), chronic bronchitis, and emphysema. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by conditional logistic regression adjusting for potential confounders. We observed an increased risk of lung cancer with history of any chronic lung disease among males (OR = 14.2; 95%CI = 4.3-46.9), females (OR = 2.6; 95%CI = 1.1-6.3), smokers (OR = 12.7; 95%CI = 3.5-45.8), and nonsmokers (OR = 2.6; 95%CI = 1.1-6.4). Specifically, TB (OR = 83.7; 95%CI = 11.0-634.7), COPD (OR = 3.2; 95%CI = 1.7-6.0), and emphysema and chronic bronchitis (OR = 3.3; 95%CI = 1.7-6.4) were associated with increased risks. These findings suggest that history of chronic lung diseases may also increase risk of lung cancer in populations with indoor coal smoke exposures.

Fried meat intake is a risk factor for lung adenocarcinoma in a prospective cohort of Chinese men and women in Singapore

Probable human carcinogens are generated during Chinese-style high-temperature cooking of meat and have been detected in the ambient air and on the meat surface. Although the inhalation of these compounds is an established risk factor for lung cancer, exposure via fried meat consumption has not yet been prospectively evaluated as a risk factor. The relationship between fried meat intake and lung cancer risk was investigated using data from a prospective cohort study among Chinese in Singapore. Lung cancer cases (n = 1130) were identified from 61 321 men and women, 70% of whom were lifetime never smokers. Proportional hazards regression methods were used to calculate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Overall, there was no association between fried meat intake and risk of all lung cancers combined. For lung adenocarcinoma, fried meat intake had a statistically significant association with increased risk. The association between fried meat intake and risk of lung adenocarcinoma became stronger when analyses were restricted to lifetime never smokers. Compared with the lowest tertile of fried meat intake, the HRs (95% CIs) for the second and third tertiles were 1.43 (0.98, 2.08) and 1.51 (1.03, 2.22), respectively (P for trend = 0.04). The positive association was present among both men and women. There was no association between fried meat intake and risk of non-adenocarcinomas of the lung. Our prospective results for fried meat intake support consumption as an important route of exposure to compounds from Chinese-style high-temperature cooking for the development of lung adenocarcinoma.

Indoor air pollution and risk of lung cancer among Chinese female non-smokers

PURPOSE

To investigate indoor particulate matter (PM) level and various indoor air pollution exposure, and to examine their relationships with risk of lung cancer in an urban Chinese population, with a focus on non-smoking women.

METHODS

We conducted a case-control study in Taiyuan, China, consisting of 399 lung cancer cases and 466 controls, of which 164 cases and 218 controls were female non-smokers. Indoor PM concentrations, including PM(1), PM(2.5), PM(7), PM(10), and TSP, were measured using a particle mass monitor. Unconditional logistic regression models were used to calculate odds ratios (ORs) and 95 % confidence intervals after adjusting for age, education, annual income, and smoking.

RESULTS

Among non-smoking women, lung cancer was strongly associated with multiple sources of indoor air pollution 10 years ago, including heavy exposure to environmental tobacco smoke at work (aOR = 3.65), high frequency of cooking (aOR = 3.30), and solid fuel usage for cooking (aOR = 4.08) and heating (aOR(coal stove) = 2.00). Housing characteristics related to poor ventilation, including single-story, less window area, no separate kitchen, no ventilator, and rarely having windows open, are associated with lung cancer. Indoor medium PM(2.5) concentration was 68 μg/m(3), and PM(10) was 230 μg/m(3). PM levels in winter are strongly correlated with solid fuel usage for cooking, heating, and ventilators. PM(1) levels in cases are more than 3 times higher than that in controls. Every 10 μg/m(3) increase in PM(1) is associated with 45 % increased risk of lung cancer.

CONCLUSIONS

Indoor air pollution plays an important role in the development of lung cancer among non-smoking Chinese women.

Indoor air pollution from solid fuels and risk of upper aerodigestive tract cancers in central and eastern Europe

BACKGROUND

Indoor air pollution from solid fuels is a potentially important risk factor for cancer, yet data on cancers from organs other than the lung are scarce. We investigated if indoor air pollution from coal and wood are risk factors for additional cancers, particularly that of the upper aerodigestive tract (oral cavity, larynx, pharynx and esophagus) in the high-risk areas of central and eastern Europe.

METHODS

We used data from multi-center hospital-based case-control study of 1065 histologically confirmed upper aerodigestive tract cancer cases and 1346 controls. Standardized questionnaires were used to collect information on residential fuel use for cooking and heating. Using unconditional logistic regression, we calculated odds ratios (ORs) and 95% confidence intervals (95% CIs) for upper aerodigestive tract cancer risk after adjusting for potential confounders.

RESULTS

Lifelong wood use was associated with pharyngeal and esophageal (OR 4.05, 95% CI: 1.30-12.68 and OR 2.71, 95% CI: 1.21-6.10, respectively). We observed an exposure-response relationship between duration of wood use and risk of pharyngeal cancer among those who had never used coal (P(trend)=0.04), ruling out the possibility of residual confounding by coal. Similarly, we observed an increased risk of laryngeal cancers and head & neck cancers among those who always used coal, with a noted exposure-response relationship (P(trend)<0.01).

CONCLUSIONS

Our results suggest a possible role of indoor air pollution from solid fuel use in head and neck carcinogenesis in the high risk area of central and eastern Europe.

Determination of benzo[a]pyrene and dibenzopyrenes in a Chinese coal fly ash certified reference material

Air pollution from coal combustion is of great concern in China because coal is the country's principal source of energy and it has been estimated that coal combustion is one of the main sources of polycyclic aromatic hydrocarbon (PAH) emissions in the nation. This study reports the concentrations of 15 PAHs including benzo[a]pyrene, dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene in a coal fly ash certified reference material (CRM) from China. To the best of our knowledge, dibenzo[a,l]pyrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene concentrations in coal fly ash particles have not previously been reported. Benzo[a]pyrene is the only one of the studied hydrocarbons whose concentration in the coal fly ash CRM had previously been certified. The concentration of this species measured in this present work was twice the certified value. This is probably because of the exhaustive accelerated solvent extraction method employed. Consecutive extractions indicated an extraction recovery in excess of 95% for benzo[a]pyrene. For the other determined PAHs, repeat extractions indicated recoveries above 90%.

Smoking and air pollution exposure and lung cancer mortality in Zhaoyuan County

BACKGROUND

Simultaneous exposure to high levels of air pollution and high tobacco consumption at the same place is rare. The aim of the present study was to evaluate the impact of the two factors on the risk of developing lung cancer.

METHODS

Data on the number of deaths due to lung cancer and on population from 1970 to 2009 were obtained from Zhaoyuan County. Data on the smoking populations were obtained at random sampling survey during the time in Zhaoyuan. Data on the components of atmospheric surveillance were obtained from the local environmental protection offices. Logarithmic linear regression and general log-linear Poisson age-period-cohort (APC) models were used to estimate age, period, cohort, gender, smoking, and air pollution effects on the risk of lung cancer mortality.

RESULTS

The standardized mortality rates of lung cancer drastically increased from 8.43 in per 100 000 individuals in the 1970-1974 to 25.67 in per 100 000 individuals in the 2005-2009 death survey. The annual change of lung cancer mortality was 3.20%. In the log linear regression model, the age, proportion of smokers, gender, period, and air pollution are significantly associated with lung cancer mortality. The APC analysis shows that the relative risks (RRs) of gender, smoking, and air pollution are 2.29 (95% confidence interval (CI): 2.16-2.43), 3.05 (95% CI = 2.76-3.36), and 1.42 (95% CI = 1.19-1.69), respectively. Compared with the period 1970-1974, high RRs were found during 1995-2009. Compared with the birth cohort 1950-1954, the RRs increased in the birth cohorts of 1910 to the 1940. Compared the aged 35-59 and 60-84 in the 1980-1984 death survey (not exposed to air pollution) with that in the 2005-2009 death survey (exposed to air pollution), The two age groups exposed to air pollution, 25 years later, had an increased mortality rates for lung cancer by 2.27 and 3.55 times for males and by 1.47 and 3.35 times for females.

CONCLUSION

The mortality rates of lung cancer drastically increased in the past 35 years. The trend of lung cancer mortality may be in a great extent possibly due to the effects of combined smoking and air pollution exposure.

Chapter 6: Lung cancer in never smokers: epidemiology and risk prediction models

In this chapter we review the epidemiology of lung cancer incidence and mortality among never smokers/nonsmokers and describe the never smoker lung cancer risk models used by the Cancer Intervention and Surveillance Network (CISNET) modelers. Our review focuses on those influences likely to have measurable population impact on never smoker risk, such as secondhand smoke, even though the individual-level impact may be small. Occupational exposures may also contribute importantly to the population attributable risk of lung cancer. We examine the following risk factors in this chapter: age, environmental tobacco smoke, cooking fumes, ionizing radiation including radon gas, inherited genetic susceptibility, selected occupational exposures, preexisting lung disease, and oncogenic viruses. We also compare the prevalence of never smokers between the three CISNET smoking scenarios and present the corresponding lung cancer mortality estimates among never smokers as predicted by a typical CISNET model.

Differences in plasma MMPs and TIMPs protein expression and chemotherapy response in patients with tobacco- or wood-smoke-induced lung cancer

BACKGROUND

One of the risk factors associated with lung cancer in never-smoker patients is wood smoke exposure (WS). However, information about its clinical and molecular characteristics remains scant.

OBJECTIVE

This was to analyze--in plasma from patients with tobacco- or wood-smoke-induced lung cancer--whether the enzymatic activity and concentration of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) differ, and to determine whether there was a correlation between these indicators of the metastatic potential and the first-line chemotherapy response.

METHODS

Patients were classified according to lung cancer associated with: the smoking of tobacco (T), WS and where no association with a known risk factor (N) could be established. The gelatinase activity of plasma MMP was analyzed by radiolabeled substrate degradation and zymography assay. Protein expression of MMPs and TIMPs was evaluated by Western blot densitometry analysis.

RESULTS

The 26.9% WS patients had a better response to therapy in comparison with the T group (OR = 4.9, 95% CI = 1.25-20.15; p = 0.019). The lowest gelatinase activity was observed in WS subjects, in comparison with T and N subjects (96.7 ± 15.9, 182.9 ± 31.5 and 163.3 ± 22.7 µg of degraded gelatin/mg of incubated plasma protein, respectively; p < 0.025); this enzymatic activity corresponded to MMP-2. The highest MMP-2, MMP-9, MT1-MMP and TIMP-1 plasma levels were observed in T subjects.

CONCLUSION

Tobacco and wood smoke have different effects on MMP and TIMP synthesis and gelatinase activity, directly influencing lung cancer metastatic potential and chemotherapy response.

Genetic variant in TP63 on locus 3q28 is associated with risk of lung adenocarcinoma among never-smoking females in Asia

A recent genome-wide association study (GWAS) of subjects from Japan and South Korea reported a novel association between the TP63 locus on chromosome 3q28 and risk of lung adenocarcinoma (p = 7.3 × 10(-12)); however, this association did not achieve genome-wide significance (p ≤ 10(-7)) among never-smoking males or females. To determine if this association with lung cancer risk is independent of tobacco use, we genotyped the TP63 SNPs reported by the previous GWAS (rs10937405 and rs4488809) in 3,467 never-smoking female lung cancer cases and 3,787 never-smoking female controls from 10 studies conducted in Taiwan, Mainland China, South Korea, and Singapore. Genetic variation in rs10937405 was associated with risk of lung adenocarcinoma [n = 2,529 cases; p = 7.1 × 10(-8); allelic risk = 0.80, 95% confidence interval (CI) = 0.74-0.87]. There was also evidence of association with squamous cell carcinoma of the lung (n = 302 cases; p = 0.037; allelic risk = 0.82, 95% CI = 0.67-0.99). Our findings provide strong evidence that genetic variation in TP63 is associated with the risk of lung adenocarcinoma among Asian females in the absence of tobacco smoking.

Polycyclic aromatic hydrocarbon burden in ambient air in selected Niger Delta communities in Nigeria

The Niger Delta area in Nigeria has major oil producing and refining centers that characterized enormous industrial activities, especially in the petroleum sector. These industrial processes release different kinds of atmospheric pollutants, of which there is paucity of information on their levels and health implications. The objective of this study was to determine the ambient levels of polycyclic aromatic hydrocarbons (PAHs) in communities of a local government area (Eleme) where oil wells, petrochemical installations, a refinery, and a fertilizer complex are located. Respirable particulate matter (PM) in air were collected using Anderson high-volume sampler with PM with aerodynamic diameter > 10 microm (PM10) inlet for collecting filterable, particle-bound PAHs according to standard methods. PAHs were analyzed following standard methods for the 16 World Health Organization (WHO) prioritized components. The results were compared against the levels in another local government area (Ahoada East) with low industrial presence. The average total PAH concentration in Eleme of 9.2 microg/m3 was among the highest in the world; by contrast, the average concentration in Ahoada East was only 0.17 ng/m3. The most prominent PAHs at Eleme were those known to be carcinogenic and included benzo(a)pyrene (1.6 x 10(4) ng/m3 at bubu), benzo(k)fluoranthene (2.4 x 10(4) ng/m3 at Akpajo where a petrochemical is located), pyrene (3.1 x 10(3) ng/m3 at Ogale), and indeno(1,2,3-cd)pyrene (9.1 x 10(3) ng/m3 at Akpajo). Data from this study emphasize the need for a comprehensive source apportionment study and an assessment of the health effects of oil production on local communities of Nigeria where no such information currently exists.

Chronic inhalation of biomass smoke is associated with DNA damage in airway cells: involvement of particulate pollutants and benzene

This study examined whether indoor air pollution from biomass fuel burning induces DNA damage in airway cells. For this, sputum cells were collected from 56 premenopausal rural women who cooked with biomass (wood, dung, crop residues) and 49 age-matched controls who cooked with cleaner liquefied petroleum gas. The levels of particulate matters with diameters of less than 10 and 2.5 µm (PM(10) and PM(2.5)) in indoor air were measured using a real-time aerosol monitor. Benzene exposure was monitored by measuring trans,trans-muconic acid (t,t-MA) in urine by HPLC-UV. DNA damage was examined by alkaline comet assay in sputum cells. Generation of reactive oxygen species (ROS) and level of superoxide dismutase (SOD) in sputum cells were measured by flow cytometry and spectrophotometry, respectively. Compared with controls, biomass users had 4 times higher tail percentage DNA, 37% more comet tail length and 5 times more Olive tail moment (p < 0.001) in inflammatory and epithelial cells in sputum, suggesting extensive DNA damage. In addition, women who cooked with biomass had 6 times higher levels of urinary t,t-MA and 2-fold higher levels of ROS generation concomitant with 28% depletion of SOD. Indoor air of biomass-using households had 2-4 times more PM(10) and PM(2.5) than that of controls. After controlling potential confounders, positive association was found between DNA damage parameters, particulate pollution, urinary t,t-MA and ROS. Thus, long-term exposure to biomass smoke induces DNA damage in airway cells and the effect was probably mediated, at least in part, by oxidative stress generated by inhaled particulate matter and benzene.

Refuelling of vehicles, the use of wood burners and the risk of acute lymphoblastic leukaemia in childhood

It is plausible that exposure of the parents before birth or of the child to sources of benzene increases the risk of childhood acute lymphoblastic leukaemia (ALL). The aim of this analysis was to investigate whether refuelling a vehicle with petrol before birth or burning wood to heat the home before or after the child's birth increased the risk of childhood ALL. Data from 389 cases and 876 frequency-matched controls were analysed using unconditional logistic regression, adjusting for study matching factors and potential confounders. The odds ratio (OR) for the mother ever refuelling a vehicle with petrol for non-occupational purposes before or during the pregnancy was 0.97 [95% confidence interval (CI) 0.69, 1.38]. The OR for the father for this exposure in the year before conception was 0.88 [95% CI 0.52, 1.48]. The OR for use of a closed wood burner to heat the home in the year before or during pregnancy was 1.41 [95% CI 1.02, 1.94] and 1.25 [95% CI 0.92, 1.70] after birth. We found no evidence that non-occupational refuelling a vehicle with petrol in the year before or during pregnancy increased the risk of ALL in the offspring. There was weak evidence that burning wood in a closed burner to heat the home increased the risk, but there was no dose-response relationship and chance could explain the finding.

Air pollution from household solid fuel combustion in India: an overview of exposure and health related information to inform health research priorities

Environmental and occupational risk factors contribute to nearly 40% of the national burden of disease in India, with air pollution in the indoor and outdoor environment ranking amongst leading risk factors. It is now recognized that the health burden from air pollution exposures that primarily occur in the rural indoors, from pollutants released during the incomplete combustion of solid fuels in households, may rival or even exceed the burden attributable to urban outdoor exposures. Few environmental epidemiological efforts have been devoted to this setting, however. We provide an overview of important available information on exposures and health effects related to household solid fuel use in India, with a view to inform health research priorities for household air pollution and facilitate being able to address air pollution within an integrated rural-urban framework in the future.

Impact of the improved patsari biomass stove on urinary polycyclic aromatic hydrocarbon biomarkers and carbon monoxide exposures in rural Mexican women

BACKGROUND

Cooking with biomass fuels on open fires results in exposure to health-damaging pollutants such as carbon monoxide (CO), polycyclic aromatic hydrocarbons (PAHs), and particulate matter.

OBJECTIVE

We compared CO exposures and urinary PAH biomarkers pre- and postintervention with an improved biomass stove, the Patsari stove.

METHODS

In a subsample of 63 women participating in a randomized controlled trial in central Mexico, we measured personal CO exposure for 8 hr during the day using continuous monitors and passive samplers. In addition, first-morning urine samples obtained the next day were analyzed for monohydroxylated PAH metabolites by gas chromatography/isotope dilution/high-resolution mass spectrometry. Exposure data were collected during the use of an open fire (preintervention) and after installation of the improved stove (postintervention) for 47 women, enabling paired comparisons.

RESULTS

Median pre- and postintervention values were 4 and 1 ppm for continuous personal CO and 3 and 1 ppm for passive sampler CO, respectively. Postintervention measurements indicated an average reduction of 42% for hydroxylated metabolites of naphthalene, fluorene, phenanthrene, and pyrene on a whole-weight concentration basis (micrograms per liter of urine), and a 34% reduction on a creatinine-adjusted basis (micrograms per gram of creatinine). Pre- and postintervention geometric mean values for 1-hydroxypyrene were 3.2 and 2.0 μg/g creatinine, respectively.

CONCLUSION

Use of the Patsari stove significantly reduced CO and PAH exposures in women. However, levels of many PAH biomarkers remained higher than those reported among smokers.

A review of diseases associated with household air pollution due to the use of biomass fuels

Nearly one third of the world's population use biomass fuels such as coal, wood, animal dung, and crop residues as their primary source of domestic energy. Due to their incomplete combustion, a multitude of pollutants associated with high levels of indoor air pollution (IAP) are released which include suspended particulate matter (SPM), carbon monoxide, formaldehyde, nitrogen dioxide, polycyclic aromatic hydrocarbons (PAH), etc. There is a line of evidence that exposure to those pollutants can lead to increased risk of diseases including respiratory infections (e.g., pneumonia, tuberculosis and chronic obstructive pulmonary disease (COPD), lung cancer, and asthma), low birth weight, cataracts, and cardiovascular events. It is one of the major global public health threats that require greater efforts for prevention through research and policy-making. This review summarizes the available information on potential health risks associated with biomass fuel use.

Evaluating the effectiveness of a commercial portable air purifier in homes with wood burning stoves: a preliminary study

Wood burning for residential heating is prevalent in the Rocky Mountain regions of the United States. Studies have shown that wood stoves can be a significant source of PM(2.5) within homes. In this study, the effectiveness of an electrostatic filter portable air purifier was evaluated (1) in a home where a wood stove was the sole heat source and (2) in a home where a wood stove was used as a supplemental heat source. Particle count concentrations in six particle sizes and particle mass concentrations in two particle sizes were measured for ten 12-hour purifier on and ten purifier off trials in each home. Particle count concentrations were reduced by 61-85 percent. Similar reductions were observed in particle mass concentrations. These findings, although limited to one season, suggest that a portable air purifier may effectively reduce indoor particulate matter concentrations associated with wood combustion during home heating.

Oxidative stress, DNA damage, and inflammation induced by ambient air and wood smoke particulate matter in human A549 and THP-1 cell lines

Combustion of biomass and wood for residential heating and/or cooking contributes substantially to both ambient air and indoor levels of particulate matter (PM). Toxicological characterization of ambient air PM, especially related to traffic, is well advanced, whereas the toxicology of wood smoke PM (WSPM) is poorly assessed. We assessed a wide spectrum of toxicity end points in human A549 lung epithelial and THP-1 monocytic cell lines comparing WSPM from high or low oxygen combustion and ambient PM collected in a village with many operating wood stoves and from a rural background area. In both cell types, all extensively characterized PM samples (1.25-100 μg/mL) induced dose-dependent formation of reactive oxygen species and DNA damage in terms of strand breaks and formamidopyrimidine DNA glycosylase sites assessed by the comet assay with WSPM being most potent. The WSPM contained more polycyclic aromatic hydrocarbons (PAH), less soluble metals, and expectedly also had a smaller particle size than PM collected from ambient air. All four types of PM combined increased the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine dose-dependently in A549 cells, whereas there was no change in the levels of etheno-adducts or bulky DNA adducts. Furthermore, mRNA expression of the proinflammatory genes monocyte chemoattractant protein-1, interleukin-8, and tumor necrosis factor-α as well as the oxidative stress gene heme oxygenase-1 was upregulated in the THP-1 cells especially by WSPM and ambient PM sampled from the wood stove area. Expression of oxoguanine glycosylase 1, lymphocyte function-associated antigen-1, and interleukin-6 did not change. We conclude that WSPM has small particle size, high level of PAH, low level of water-soluble metals, and produces high levels of free radicals, DNA damage as well as inflammatory and oxidative stress response gene expression in cultured human cells.

The precancerous effect of emitted cooking oil fumes on precursor lesions of cervical cancer

Although cooking emission from high-temperature frying has been deemed a Group 2A carcinogen by the International Agency for Research on Cancer, little is known about its impact on cervical tumorigenesis. To investigate the precancerous consequence of cooking oil fumes on cervical intraepithelial neoplasm (CIN), a community-based case-control study, which takes all known risk factors into consideration, was conducted in Taiwan. From 2003 to 2008, in a Pap smear screening and biopsy examination network, 206 pathology-verified women with inflammations/atypical squamous cells of undetermined significance or CIN grade-1 (CIN1) and 73 with CIN2-3 (defined as low-grade squamous intraepithelial lesions (LGSIL) and high-grade squamous intraepithelial lesions (HGSIL), respectively); and 1,200 area-and-age-matched controls with negative cytology were recruited. Multinomial logistic regression was applied in the multivariate analysis to determine the likelihood of contracting LGSIL or HGSIL. The risks of the two lesions increased with the increase of carcinogenic high-risk human papillomavirus DNA load, with a clear dose-response relationship. Chefs were observed to experience a 7.9-fold elevated HGSIL risk. Kitchens with poor fume ventilation during the main cooking life-stage correlated to a 3.7-fold risk of HGSIL, but not for LGSIL. More than 1 hr of daily cooking in kitchens with poor fume conditions appeared to confer an 8.4-fold HGSIL risk, with an 8.3-fold heterogeneously higher odds ratio than that (aOR = 1.0) for LGSIL. Similar risk pattern has been reproduced among never-smoking women. Our findings demonstrate the association between indoor exposure to cooking fumes from heated oil and the late development of cervical precancerous lesions. This final conclusion needs to be verified by future research.

The state of indoor air quality in Pakistan--a review

BACKGROUND AND PURPOSE

In Pakistan, almost 70% of the population lives in rural areas. Ninety-four percent of households in rural areas and 58% in urban areas depend on biomass fuels (wood, dung, and agricultural waste). These solid fuels have poor combustion efficiency. Due to incomplete combustion of the biomass fuels, the resulting smoke contains a range of health-deteriorating substances that, at varying concentrations, can pose a serious threat to human health. Indoor air pollution accounts for 28,000 deaths a year and 40 million cases of acute respiratory illness. It places a significant economic burden on Pakistan with an annual cost of 1% of GDP. Despite the mounting evidence of an association between indoor air pollution and ill health, policy makers have paid little attention to it. This review analyzes the existing information on levels of indoor air pollution in Pakistan and suggests suitable intervention methods.

METHODS

This review is focused on studies of indoor air pollution, due to biomass fuels, in Pakistan published in both scientific journals and by the Government and international organizations. In addition, the importance of environmental tobacco smoke as an indoor pollutant is highlighted.

RESULTS

Unlike many other developing countries, there are no long-term studies on the levels of indoor air pollution. The limited studies that have been undertaken indicate that indoor air pollution should be a public health concern. High levels of particulate matter and carbon monoxide have been reported, and generally, women and children are subject to the maximum exposure. There have been a few interventions, with improved stoves, in some areas since 1990. However, the effectiveness of these interventions has not been fully evaluated.

CONCLUSION

Indoor air pollution has a significant impact on the health of the population in Pakistan. The use of biomass fuel as an energy source is the biggest contributor to poor indoor air quality followed by smoking. In order to arrest the increasing levels of indoor pollution, there is a dire need to recognize it as a major health hazard and formulate a national policy to combat it. An integrated effort, with involvement of all stakeholders, could yield promising results. A countrywide public awareness campaign, on the association of indoor air pollution with ill health, followed by practical intervention would be an appropriate approach. Due to the current socioeconomic conditions in the country, development and adoption of improved cooking stoves for the population at large would be the most suitable choice. However, the potential of biogas as a fuel should be explored further, and modern fuels (natural gas and LPG) need to be accessible and economical. Smoking in closed public spaces should be banned, and knowledge of the effect of smoking on indoor air quality needs to be quantified.

Indoor air pollution from unprocessed solid fuels in developing countries

Approximately half of the world's population relies on biomass (primarily wood and agricultural residues) or coal fuels (collectively termed solid fuels) for heating, lighting, and cooking. The incomplete combustion of such materials releases byproducts with well-known adverse health effects, hence increasing the risk of many diseases and death. Among these conditions are acute respiratory infections, chronic obstructive pulmonary disease, heart disease, stroke, lung cancer, cataracts and blindness, tuberculosis, asthma, and adverse pregnancy outcomes. The International Agency for Research on Cancer has classified the indoor combustion of coal emissions as Group 1, a known carcinogen to humans. Indoor air pollution exposure is greatest in individuals who live in rural developing countries. Interventions have been limited and show only mixed results. To reduce the morbidity and mortality from indoor air pollution, countermeasures have to be developed that are practical, efficient, sustainable, and economical with involvement from the government, the commercial sector, and individuals. This review focuses on the contribution of solid fuels to indoor air pollution.

Elevated levels of volatile organic carcinogen and toxicant biomarkers in Chinese women who regularly cook at home

BACKGROUND

Epidemiologic studies associate lung cancer in nonsmoking Chinese women with Chinese-style wok cooking. Our goal was to quantify carcinogen and toxicant biomarkers in Chinese women who reported regularly doing home cooking compared with women randomly selected from the Singapore Chinese Health Study as controls.

METHODS

Biomarkers were quantified by high-performance liquid chromatography-mass spectrometry, high-performance liquid chromatography with fluorescence detection, and gas chromatography-mass spectrometry.

RESULTS

Compared with controls, women who engaged in regular home cooking had significantly higher levels of mercapturic acids of acrolein {geometric mean, 1,959 pmol/mg creatinine [95% confidence interval (95% CI), 1,554-2,467] versus 1,370 (95% CI, 1,077-1,742); P=0.038}, crotonaldehyde [geometric mean, 232 pmol/mg creatinine (95% CI, 193-277) versus 142 (95% CI, 118-171); P=0.0004], and benzene [geometric mean, 0.58 pmol/mg creatinine (95% CI, 0.44-0.78) versus 0.18 (95% CI, 0.14-0.24); P<0.0001]. No significant differences were found in levels of mercapturic acids of 1,3-butadiene, metabolites of pyrene and phenanthrene, or acetaldehyde-leukocyte DNA adduct levels between the groups. Levels of the ethylene oxide mercapturic acid were significantly higher in the controls.

CONCLUSIONS

The higher levels of the mercapturic acid of benzene, a multiorgan carcinogen, in the women who cooked are particularly notable. Overall, the results showing increased exposure to the volatile toxicants and carcinogens acrolein, crotonaldehyde, and benzene in Chinese women who regularly cook provide a plausible lead for further investigating the role of volatile compounds generated during high-temperature cooking with oils as causes of lung cancer.

IMPACT

A new direction for research on lung cancer etiology is suggested.

Cancer mortality in Europe, 2000-2004, and an overview of trends since 1975

BACKGROUND

To update the pattern of cancer mortality in Europe.

MATERIALS AND METHODS

We analysed cancer mortality in 34 European countries during 2000-2004, with an overview of trends in 1975-2004 using data from the World Health Organization.

RESULTS

From 1990-1994 to 2000-2004, overall cancer mortality in the European Union declined from 185.2 to 168.0/100 000 (world standard, -9%) in men and from 104.8 to 96.9 (-8%) in women, with larger falls in middle age. Total cancer mortality trends were favourable, though to a variable degree, in all major European countries, including Russia, but not in Romania. The major determinants of these favourable trends were the decline of lung (-16%) and other tobacco-related cancers in men, together with the persistent falls in gastric cancer, and the recent appreciable falls in colorectal cancer. In women, relevant contributions came from the persistent decline in cervical cancer and the recent falls in breast cancer mortality, particularly in northern and western Europe. Favourable trends were also observed for testicular cancer, Hodgkin lymphomas, leukaemias, and other neoplasms amenable to treatment, though the reductions were still appreciably smaller in eastern Europe.

CONCLUSION

This updated analysis of cancer mortality in Europe showed a persistent favourable trend over the last years.

Health effects of residential wood smoke particles: the importance of combustion conditions and physicochemical particle properties

BACKGROUND

Residential wood combustion is now recognized as a major particle source in many developed countries, and the number of studies investigating the negative health effects associated with wood smoke exposure is currently increasing. The combustion appliances in use today provide highly variable combustion conditions resulting in large variations in the physicochemical characteristics of the emitted particles. These differences in physicochemical properties are likely to influence the biological effects induced by the wood smoke particles.

OUTLINE

The focus of this review is to discuss the present knowledge on physicochemical properties of wood smoke particles from different combustion conditions in relation to wood smoke-induced health effects. In addition, the human wood smoke exposure in developed countries is explored in order to identify the particle characteristics that are relevant for experimental studies of wood smoke-induced health effects. Finally, recent experimental studies regarding wood smoke exposure are discussed with respect to the applied combustion conditions and particle properties.

CONCLUSION

Overall, the reviewed literature regarding the physicochemical properties of wood smoke particles provides a relatively clear picture of how these properties vary with the combustion conditions, whereas particle emissions from specific classes of combustion appliances are less well characterised. The major gaps in knowledge concern; (i) characterisation of the atmospheric transformations of wood smoke particles, (ii) characterisation of the physicochemical properties of wood smoke particles in ambient and indoor environments, and (iii) identification of the physicochemical properties that influence the biological effects of wood smoke particles.

Indoor air pollution as a lung health hazard: focus on populous countries

PURPOSE OF REVIEW

Indoor air pollution (IAP) resulting from the use of solid fuel for cooking and heating is a significant public health concern in developing countries. Recent studies have attempted to better characterize the epidemiology of IAP in respiratory diseases and develop technologies for reducing this IAP exposure.

RECENT FINDINGS

Evidence showed that IAP resulting from solid fuel smoke is a causative or contributory factor to acute respiratory infection, chronic obstructive lung disease, asthma, lung cancer and tuberculosis. Evidence also showed that health education, improvements in household ventilation and area distribution, improvements in stoves and changes of the fuels for cooking and heating can reduce IAP.

SUMMARY

Evidence of impacts of IAP on respiratory system disease is strong. Although some technologies can improve indoor air quality in households, improving it in households is still an urgent and high-priority task. Longitudinal studies using different methods of exposure assessment that include both chemical measurements and activity data, with longer follow-up and larger samples, are needed. Any program for the prevention of IAP must be based on what is acceptable to the community, and the effects of the intervention must be evaluated.

Genetic variation in telomere maintenance genes, telomere length, and lung cancer susceptibility

Telomeres are responsible for the protection of the chromosome ends and shortened telomere length has been associated with risk of multiple cancers. Genetic variation in telomere-related genes may alter cancer risk associated with telomere length. Using lung cancer cases (n=120) and population-based controls (n=110) from Xuanwei, China, we analyzed telomere length separately and in conjunction with single nucleotide polymorphisms in the telomere maintenance genes POT1, TERT, and TERF2, which we have previously reported were associated with risk of lung cancer in this study. POT1 rs10244817, TERT rs2075786, and TERF2 rs251796 were significantly associated with lung cancer (p(trend)< or =0.05). The shortest tertile of telomere length was not significantly associated with risk of lung cancer (OR=1.58; 95% CI=0.79-3.18) when compared to the longest tertile of telomere length. When stratified by genotype, there was a suggestion of a dose-response relationship between tertiles of telomere length and risk of lung cancer among the POT1 rs10244817 common variant carriers (OR (95% CI)=1.33 (0.47-3.75), 3.30 (1.14-9.56), respectively) but not among variant genotype carriers (p(interaction)=0.05). Our findings provide evidence that telomere length and genetic variation in telomere maintenance genes may be associated with risk of lung cancer susceptibility and warrant replication in larger studies.

Urinary 1-hydroxypyrene and PAH exposure in 4-year-old Spanish children

AIMS

Exposure to polycyclic aromatic hydrocarbons (PAH), among the main compounds present in polluted urban air, is of concern for children's health. Childhood exposure to PAH was assessed by urinary monitoring of 1-hydroxypyrene (1-OHP), a pyrene metabolite, investigating its association with exposure to air pollution and other factors related to PAH in air.

METHODS

A group of 174 4-year-old children were recruited and a questionnaire on their indoor and outdoor residential environment was completed by parents. At the same time, environmental measurements of traffic-related air pollution (NO2) were carried out. A urine sample was collected from each child in order to analyze 1-OHP using HPLC with fluorescence detection, correcting for creatinine concentrations. Non-parametric tests and regression analyses were used to identify environmental factors that influence 1-OHP excretion.

RESULTS

Mean urinary 1-OHP concentration was 0.061 micromol/mol creatinine, ranging from 0.004 to 0.314 micromol/mol. Non-parametric tests and regression analysis showed positive and significant associations (P<or=0.05) between 1-OHP and predicted residential exposure to NO2 (which was based on outdoor environmental measurements and geo-statistical analysis), self-reported residential vehicle traffic, passive smoking and cooking appliance. 1-OHP levels tended to be higher among children living in urban areas (0.062 micromol/mol vs. 0.058 micromol/mol for children living in rural areas) but differences were not significant (P=0.20).

CONCLUSION

In Southern Spain, concentrations of urinary 1-OHP were in the lower range of those generally reported for children living in non-polluted areas in Western Europe and the USA. Traffic-related air pollution, passive smoking and cooking appliance influenced urinary 1-OHP level in the children, which should be prevented due to the health consequences of the inadvertent exposure to PAH during development.

The roles of smoking and cooking emissions in lung cancer risk among Chinese women in Hong Kong

BACKGROUND

We conducted this case-control study to evaluate smoking effect on lung cancer conditional on the level of exposure to cooking emissions and to explore whether there is a joint effect of these two risk factors.

SUBJECTS AND METHODS

We selected 279 newly diagnosed primary lung cancer cases and 322 community controls from Hong Kong females, frequency matched by age group, and collected relevant data. We applied logistic regression to estimate lung cancer risk related to smoking and cooking fume exposure, expressed as total cooking dish-years, while adjusting for various potential confounding factors.

RESULTS

Current smoking was associated with four-fold increased risk, and ex-smoking with two-fold risk, which was not much influenced by cooking dish-years. No increased risk was observed in environmental tobacco smoking. Increasing intakes of yellow/orange vegetables and multivitamins were significant protective factors in all models. In the analysis of joint effect, the combination of smoking and cooking dish-years tended to have a greater risk than exposure to cooking fumes alone. There was a dose-response gradient with total dish-years in nonsmokers, but not in smokers. Smoking was more strongly associated with nonadenocarcinoma, whereas exposure to cooking fumes appeared to be related to both adenocarcinoma and nonadenocarcinoma.

CONCLUSION

We confirmed the important roles of smoking and cooking emissions in lung cancer risk among the women. These two major risk factors appeared to act independently.

Portable stove use is associated with lower lung cancer mortality risk in lifetime smoky coal users

Domestic fuel combustion from cooking and heating, to which about 3 billion people worldwide are exposed, is associated with increased lung cancer risk. Lung cancer incidence in Xuanwei is the highest in China, and the attributable risk of lung cancer from unvented smoky coal burning is greater than 90%. To evaluate any lung cancer mortality reduction after changing from unvented stoves to portable stoves, we used lifetime smoky coal users in a retrospective cohort of all farmers born during 1917–1951 and residing in Xuanwei in 1976. Of the 42 422 enrolled farmers, 4054 lifetime smoky coal users changed to portable stoves, 4364 did not change, and 1074 died of lung cancer. Lung cancer morality associated with stove change was assessed by product-limit survival curves and multivariate Cox regression models. Both men (P<0.0001) and women (P<0.0001) who changed to portable stoves had a significantly increased probability of survival compared with those who did not change. Portable stoves were associated with decreased risk of lung cancer mortality in male participants (hazard ratio (HR)=0.62, 95% confidence interval (CI)=0.46–0.82) and female participants (HR=0.41, 95% CI=0.29–0.57). Portable stove use is associated with reduced lung cancer mortality risk, highlighting a cost-effective intervention that could substantially benefit health in developing countries.

Seasonal variation of polycyclic aromatic hydrocarbons (PAHs) emissions in China

A regression model based on the provincial energy consumption data was developed to calculate the monthly proportions of residential energy consumption compared to the total year volume. This model was also validated by comparing with some survey and statistical data. With this model, a PAHs emission inventory with seasonal variation was developed. The seasonal variations of different sources in different regions of China and the spatial distribution of the major sources in different seasons were also achieved. The PAHs emissions were larger in the winter than in the summer, with a difference of about 1.3-folds between the months with the largest and the smallest emissions. Residential solid fuel combustion dominated the pattern of seasonal variation with the winter-time emissions as much as 1.6 times as that in the summer, while the emissions from wild fires and open fire straw burning was mainly concentrated during the spring and summer.

Particle dose estimation from frying in residential settings

Fumes produced during frying have been implicated as a potential cause for the increased incidence of adenocarcinoma. Particulate matter exposure has also been linked with other pulmonary and coronary disease. This study investigated the contribution of frying in residential settings to ultrafine and fine particulate matter (UFP, PM2.5, respectively) exposure in homes. Production rates of 44 +/- 26 particles (pt)/cm3 s (mean +/- standard deviation) and 0.13 +/- 0.12 microg/m3 s were found for UFP and PM2.5, respectively, from frying a variety of foods at medium heat in a loft-style apartment. Rates of 290 +/- 150 pt/cm3 s and 3.5 +/- 4.9 microg/m3 s were found for UFP and PM2.5, respectively, from frying with vegetable oil alone in five homes; the higher rates were ascribed to differences between the homes rather than the absence of food. The elimination of UFP and PM2.5 was found to be primarily through exhaust fans in these homes, and it was found to follow a first-order process with an elimination rate constant of 6.1 x 10(-4) +/- 2.5 x 10(-4) s(-1). The dose to an individual from frying was estimated based on the measured production and elimination rates and found to be significant when compared with the typical daily dose incurred within a home because of outside sources.

PRACTICAL IMPLICATIONS

The contribution of indoor sources to particulate matter exposure in homes remains poorly understood. Yet common household activities such as frying may produce substantial concentrations of potentially toxic particles. Because of the potential adverse health impacts associated with exposure to air pollution, potentially vulnerable individuals may be advised to remain indoors at certain times so as to reduce their overall exposure. Such interventions can be negated without proper guidance regarding the exposure involved in various indoor activities such as cooking. This paper outlines a methodology to estimate the dose to particulate matter incurred during frying and shows that this can represent a significant source of daily exposure.

Variation in lung cancer risk by smoky coal subtype in Xuanwei, China

Lung cancer rates in Xuanwei County have been among the highest in China for both males and females and have been causally associated with exposure to indoor smoky (bituminous) coal emissions that contain very high levels of polycyclic aromatic hydrocarbons. There are numerous coal mines across the County. Although lung cancer risk is strongly associated with the use of smoky coal as a whole, variation in risk by smoky coal subtype has not been characterized as yet. We conducted a population-based case-control study of 498 lung cancer cases and 498 controls, individually matched to case subjects on age (+/-2 years) and sex to examine risk by coal subtype. Odds ratios (ORs) and 95% confidence intervals (CIs) for coal subtype were calculated by conditional logistic regression, adjusting for potential confounders. Overall, smoky coal use was positively and statistically significantly associated with lung cancer risk, when compared with the use of smokeless coal or wood (OR = 7.7, 95% CI = 4.5-13.3). Furthermore, there was a marked heterogeneity in risk estimates for specific subtypes of smoky coal (test for heterogeneity: p = 5.17 x 10(-10)). Estimates were highest for coal of the Laibin (OR = 24.8, 95% CI = 12.4-49.6) and Longtan (OR = 11.6, 95% CI = 5.0-27.2) coal types and lower for coal from other subtypes. These findings strongly suggest that in Xuanwei and elsewhere, the carcinogenic potential of coal combustion products can exhibit substantial local variation by specific coal source.