Urinary 1-hydroxypyrene, air pollution exposure and associated life style factors in pregnant women

1-hydroxypyrene (1-OHP) is a biomarker of exposure to polycyclic aromatic hydrocarbons (PAHs). PAHs are pollutants produced by the combustion of organic material, and could be found both indoors and outdoors. Prenatal exposure to these compounds has been associated with retarded intrauterine growth and respiratory problems in children. The objective of this study is to describe the 1-OHP levels in urine in pregnant women in the INMA cohort in Valencia, and to study the association with socio-demographic and lifestyle variables, as well as with indicators of air pollution. The study population is a sub-sample (n: 204) of a cohort of pregnant women in the multicentre INMA project in Valencia (Spain). Urine samples were taken in week 12 of gestation, and 1-OHP was analyzed, and adjusted for creatinine. Socio-demographic and lifestyle information was collected using a questionnaire. Data from the monitoring stations in Valencia were used to assign levels of exposure to nitrogen dioxide (NO2), sulphur dioxide (SO2), total suspended particulates (TSP) and carbon monoxide (CO). The median 1-OHP level was 0.061 muicrool/mol of creatinine. Women who smoked had higher 1-OHP levels (0.095 micromol/mol of creatinine) than non-smokers (0.050 micromol/mol of creatinine). The variables predicting 1-OHP levels on linear multivariate analysis were: tobacco consumption, consumption of fried and smoked foods. There was also a significant association with NO2 levels 4 and 5 days before the samples were taken. The 1-OHP levels found in pregnant women in Valencia were higher than those found among women in reports in USA. 1-hydroxypyrene could be a good marker of exposure to PAHs from tobacco and diet, and also a useful marker of short term exposure to air pollution.     

Elevated concentrations of 1-hydroxypyrene in schoolchildren during winter in Christchurch, New Zealand

Particulate air pollution is significantly elevated during the winter in Christchurch, New Zealand, largely attributable to use of wood burners for domestic home heating, topography, and meteorological conditions. Polycyclic aromatic hydrocarbons (PAHs) are a key component of airborne particulate matter (PM) and urinary 1-hydroxypyrene (1-OHP) has previously been used to assess exposure of people to PAHs. We examined urinary 1-OHP in Christchurch male non-smoking schoolchildren (12-18 yr) on two occasions after high pollution events (48 and 72 microg PM(10)/m(3) 24-h average) and two occasions during periods of low pollution (19 and 12 microg PM(10)/m(3)). Concentrations of urinary 1-OHP were significantly elevated in the students during high pollution events (median (mean+/-SD) 0.043 (0.051+/-0.032) and 0.042 (0.060+/-0.092) micromol OHP/mol creatinine respectively) compared with low pollution periods (median (mean+/-SD) 0.019 (0.026+/-0.032) and 0.025 (0.028+/-0.018) micromol/mol creatinine respectively). The observed 1-OHP concentrations are at the lower end of those determined in children and non-occupationally exposed adults in international studies and suggest a generally low exposure to PAHs. The increased urinary 1-OHP concentrations following nights of elevated particulate concentrations in ambient air suggest increased exposure to ambient air pollution during winter time, and could potentially be used as a biomarker of exposure in this population.     

Indoor air pollution from biomass combustion and respiratory symptoms of women and children in a Zimbabwean village

Rural areas of developing countries are particularly reliant on biomass for cooking and heating. Women and children in these areas are often exposed to high levels of pollutants from biomass combustion that is associated with a range of respiratory symptoms. Domestic exposure to carbon monoxide (CO) and respirable particles (RSPs) in association with respiratory symptoms among women and children in Zimbabwe was investigated in 48 households. Health status and household characteristics were also recorded. In this study, indoor levels of CO and RSPs exceeded World Health Organization (WHO) air quality guidelines in over 95% of kitchens. The level of indoor air pollutants was associated with the area of kitchen windows and the length of cooking time combined with the level of fire combustion. Prevalence of respiratory symptoms was 94% for women and 77% for children. In addition, women reporting respiratory symptoms were exposed to higher levels of RSPs when compared with those reporting no respiratory symptoms. The study results indicated that levels of indoor air pollutants in rural Zimbabwe may contribute to respiratory symptoms in both women and children. PRACTICAL IMPLICATIONS: Levels of respirable particles and carbon monoxide in kitchens in rural Zimbabwe are unacceptably high and measures to reduce levels should be undertaken. Based on the study findings, recommendations for increasing the area of kitchen windows may be considered as a practical method of reducing indoor air pollutants in rural Zimbabwe.     

Analysis of indoor PM2.5 exposure in Asian countries using time use survey

Most household fuels used in Asian countries are solid fuels such as coal and biomass (firewood, crop residue and animal dung). The particulate matter (PM), CO, NOx and SOx produced through the combustion of these fuels inside the residence for cooking and heating has an adverse impact on people's health. PM 2.5 in particular, consisting of particles with an aerodynamic diameter of 2.5 μm or less, penetrates deep into the lungs and causes respiratory system and circulatory system diseases and so on. As a result, the World Health Organization (WHO) established guideline values for this type of particulate matter in 2005. In this study, the authors focused on PM 2.5 and estimated indoor exposure concentrations for PM 2.5 in 15 Asian countries. For each environment used for cooking, eating, heating and illumination in which people are present temporarily (microenvironment), exposure concentrations were estimated for individual cohorts categorized according to sex, age and occupation status. To establish the residence time in each microenvironment for each of the cohorts, data from time use surveys conducted in individual countries were used. China had the highest estimate for average exposure concentration in microenvironment used for cooking at 427.5 μg/m³ , followed by Nepal, Laos and India at 285.2 μg/m³, 266.3 μg/m³ and 205.7 μg/m³ , respectively. The study found that, in each country, the PM2.5 exposure concentration was highest for children and unemployed women between the ages of 35 and 64. The study also found that the exposure concentration for individual cohorts in each country was greatly affected by people's use of time indoors. Because differences in individual daily life activities were reflected in the use of time and linked to an assessment of exposure to indoor air-polluting substances, the study enabled detailed assessment of the impact of exposure.     

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 μmol/mol creatinine, ranging from 0.004 to 0.314 μmol/mol. Non-parametric tests and regression analysis showed positive and significant associations (P ≤ 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 μmol/mol vs. 0.058 μmol/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.     

Effects of genetic polymorphisms CYP1A1, GSTM1, GSTT1 and GSTP1 on urinary 1-hydroxypyrene levels in sugarcane workers

Sugarcane workers in Brazil are exposed to various genotoxic compounds, including polycyclic aromatic hydrocarbons (PAHs), derived from an incomplete combustion process of burnt sugarcane fields. The effects of the occupational exposure to sugarcane fields burning were measured in urine samples of sugarcane workers from the northwest of the State of S?o Paulo when exposed (harvesting) and when non-exposed (non-harvesting). The urinary levels of 1-hydroxypyrene (1-OHP) and the influence of the genetic polymorphisms CYP1A1, GSTM1, GSTT1 and GSTP1 were evaluated. Our results showed that the 1-OHP levels were significantly higher (P<0.0000) in the exposed sugarcane workers (0.318 mumol mol(-1) creatinine) than in the non-exposed workers (0.035 mumol mol(-1) creatinine). In an unvaried analysis, no influence regarding the polymorphisms was observed. However, multivariate regression analysis showed that the CYP1A1()4 polymorphism in the exposed group, and age and the GSTP1 polymorphism in the non-exposed group significantly influenced urinary 1-OHP excretion levels (P<0.10). The same group of sugarcane workers was significantly more exposed to PAHs during the harvesting period than during the non-harvesting period.     

Effect of Indoor air pollution from biomass and solid fuel combustion on symptoms of preeclampsia/eclampsia in Indian women

Available evidence concerning the association between indoor air pollution (IAP) from biomass and solid fuel combustion and preeclampsia/eclampsia is not available in developing countries. We investigated the association between exposure to IAP from biomass and solid fuel combustion and symptoms of preeclampsia/eclampsia in Indian women by analyzing cross‐sectional data from India's third National Family Health Survey (NFHS‐3, 2005–2006). Self‐reported symptoms of preeclampsia/eclampsia during pregnancy such as convulsions (not from fever), swelling of legs, body or face, excessive fatigue or vision difficulty during daylight, were obtained from 39 657 women aged 15–49 years who had a live birth in the previous 5 years. Effects of exposure to cooking smoke, ascertained by type of fuel used for cooking on preeclampsia/eclampsia risk, were estimated using logistic regression after adjusting for various confounders. Results indicate that women living in households using biomass and solid fuels have two times higher likelihood of reporting preeclampsia/eclampsia symptoms than do those living in households using cleaner fuels (OR = 2.21; 95%: 1.26–3.87; P = 0.006), even after controlling for the effects of a number of potentially confounding factors. This study is the first to empirically estimate the associations of IAP from biomass and solid fuel combustion and reported symptoms suggestive of preeclampsia/eclampsia in a large nationally representative sample of Indian women and we observed increased risk. These findings have important program and policy implications for countries such as India, where large proportions of the population rely on polluting biomass fuels for cooking and space heating. More epidemiological research with detailed exposure assessments and clinical measures of preeclampsia/eclampsia is needed in a developing country setting to validate these findings.     

Household air pollution from wood burning in two reconstructed houses from the Danish Viking Age

During 13 winter weeks, an experimental archeology project was undertaken in two Danish reconstructed Viking Age houses with indoor open fireplaces. Volunteers inhabited the houses under living conditions similar to those of the Viking Age, including cooking and heating by wood fire. Carbon monoxide (CO) and particulate matter (PM_2.5) were measured at varying distances to the fireplace. Near the fireplaces CO (mean) was 16 ppm. PM_2.5 (mean) was 3.40 mg/m³, however, measured in one house only. The CO:PM mass ratio was found to increase from 6.4 to 22 when increasing the distance to the fire. Two persons carried CO sensors. Average personal exposure was 6.9 ppm, and from this, a personal PM_2.5 exposure of 0.41 mg/m³ was estimated. The levels found here were higher than reported from modern studies conducted in dwellings using biomass for cooking and heating. While this may be due to the Viking house design, the volunteer's lack of training in attending a fire maybe also played a role. Even so, when comparing to today's issues arising from the use of open fires, it must be assumed that also during the Viking Age, the exposure to woodsmoke was a contributing factor to health problems.     

PAH exposure in a Ghanaian population at high risk for aflatoxicosis

It was postulated that a population in sub-Saharan Africa, known to be at high risk for aflatoxicosis due to frequent ingestion of aflatoxin (AF)-contaminated foods could also be exposed to polycyclic aromatic hydrocarbons (PAHs) from a variety of environmental sources. Previously, participants in this population were shown to be highly exposed to AFs, and this exposure was significantly reduced by intervention with NovaSil clay (NS). Objectives of this study were 1) to assess PAH exposure in participants from the AF study using urinary biomarker 1-hydroxypyrene (1-OHP); 2) examine the effect of NS clay and placebo (cellulose) treatment on 1-OHP levels; and 3) determine potential association(s) between AF and PAH exposures. A clinical trial was conducted in 177 Ghanaians who received either NS capsules as high dose or low dose, or placebo (cellulose) for a period of 3 months. At the start and end of the study, urine samples were analyzed for 1-OHP. Of the 279 total samples, 98.9% had detectable levels of 1-OHP. Median 1-OHP excretion in nonsmokers was 0.64 µmol/mol creatinine at baseline and 0.69 µmol/mol creatinine after 3 months. Samples collected at both time points did not show significant differences between placebo and NS-treated groups. There was no linear correlation between 1-OHP and AF-albumin adduct levels. Results show that this population is highly exposed to PAHs (and AFs), that NS and cellulose treatment had no statistically significant effect on 1-OHP levels, and that this urinary biomarker was not linearly related with AF exposure.     

The exposure of temple workers to polycyclic aromatic hydrocarbons

Five temples, each a different size, were selected for this study. Two of the temples were located in Taichung City (in central Taiwan), and three were in Tainan City (in Southern Taiwan). Aerosols smaller than 10 microm aerodynamic diameter (PM(10)) were collected by using personal collection samplers during pilgrim days (the first and fifteenth day of each lunar month) and normal days (all other days). Regression analysis showed that about 1.6 microg/m(3) of PM(10) contributed to the workers' exposure in the temples for each joss stick increase in the censer. The concentrations of total polycyclic aromatic hydrocarbons (t-PAHs) and carcinogenic PAHs (car-PAHs) on pilgrim days were higher than those on normal days. Mean concentrations of urinary 1-hydroxypyrene (1-OHP) in the pre-shift and post-shift workers of the five temples on normal days were 1.20 and 1.61 microg/g creatinine, respectively. Furthermore, the post-shift concentrations of 1-OHP in the workers of temples on pilgrim days were all higher than those of the workers of corresponding temples on normal days. Significant relationships between the urinary concentrations of 1-OHP and the exposure concentrations of pyrene, total PAHs and BaP(eq) were found in the workers of the temples. Results of linear regression showed that the increase of unit concentration (1 ng/m(3)) of pyrene led to a 0.05 microg/g creatinine increase of urinary 1-OHP, while the increase of unit concentration (1 ng/m(3)) of BaP(eq) resulted in an increase of 0.03 microg/g creatinine of urinary 1-OHP.     

辽宁省农村住宅的采暖方式与能耗研究

由于"烧柴火做饭,用火炕取暖"一直是北方广大农村的传统习惯.在农村能源消耗的构成中,生产耗能占20.3%,生活耗能占79.7%.在生活耗能中,常规能源,如煤、柴油、电仅占20%,其他80%要靠秸秆、柴草及牛粪等.而这80%的能源几乎都是围绕炕、灶这两样生活中心所消耗的.着重探讨了采暖与炊事这两方面的能耗,做好农村炕灶的节能也是减少直接消耗能源的有利途径.     

The influence of metabolic gene polymorphisms on urinary 1-hydroxypyrene concentrations in Chinese coke oven workers

Urinary 1-hydroxypyrene (1-OHP), a biomarker of polycyclic aromatic hydrocarbons (PAHs) exposure, may be influenced by metabolic gene polymorphisms. Such knowledge could benefit us in understanding the inter-individual difference in the mechanism of PAHs-induced carcinogenesis. We investigated the influence of gene polymorphisms on urinary 1-OHP concentrations in 447 coke oven workers from two coking plants in south China. After adjustment for age, plant, level of occupational exposure, body mass index, level of education, alcohol consumption, cigarette smoking and respirator usage, AhR R554K (rs2066853), UGT1A1 -3263T>G (rs4124874) and GSTP1 I105V (rs1695) were associated with urinary 1-OHP excretion with the p-value of 0.053, 0.006 and 0.021, respectively. The concentrations of urinary 1-OHP (Geometric mean, micromol/mol creatinine) in the homozygous major variant carriers and homozygous minor variant carriers for AhR R554K, UGT1A1 -3263T>G and GSTP1 I105V were listed as follows: 4.20 and 5.12, 5.11 and 3.92, 4.93 and 2.91, respectively. GSTT1 present carriers had a significantly higher urinary 1-OHP level than that in null carriers in the case with AhR R554K GA/AA carriers (5.17 vs. 3.64 micromol/mol creatinine, p=0.038), as well as in the case with UGT1A1 -3263T>G TG/GG carriers (5.67 vs. 3.38 micromol/mol creatinine, p=0.001). These results showed that AhR, UGT1A1, GSTP1 and GSTT1 polymorphisms were associated with urinary 1-OHP concentrations in Chinese coke oven workers. No influence was found in the association between urinary 1-OHP and other genetic polymorphisms such as CYP1A1, CYP1A2, CYP1B1, CYP2E1, EPHX1, EPHX2 in this population.     

Indoor air pollution from particulate matter emissions in different households in rural areas of Bangladesh

Indoor air pollution from the combustion of traditional biomass fuels (wood, cow dung, and crop wastes) is a significant public health problem predominantly for poor populations in many developing countries. It is particularly problematic for the women who are normally responsible for food preparation and cooking, and for infants/young children who spend time around their mothers near the cooking area. Airborne particulate matter (PM) samples were collected from cooking and living areas in homes in a rural area of Bangladesh to investigate the impact of fuel use, kitchen configurations, and ventilation on indoor air quality and to apportion the source contributions of the measured trace metals and BC concentrations. Lower PM concentrations were observed when liquefied petroleum gas (LPG) was used for cooking. PM concentrations varied significantly depending on the position of kitchen, fuel use and ventilation rates. From reconstructed mass (RCM) calculations, it was found that the major constituent of the PM was carbonaceous matter. Soil and smoke were identified as components from elemental composition data. It was also found that some kitchen configurations have lower PM concentrations than others even with the use of low-grade biomass fuels. Adoption of these kitchen configurations would be a cost-effective approach in reducing exposures from cooking in these rural areas.     

Environmental monitoring of benzene and toluene produced in indoor air due to combustion of solid biomass fuels

Exposure to benzene and toluene from the combustion of solid biomass fuels is one of the important causes of morbidity and mortality in developing countries. In this study, we assessed the exposure of cooks to benzene and toluene from biomass fuel combustion in 55 rural homes. The GC-MS was used for quantification while a personnel sampler was used for environmental monitoring. The benzene exposure differed significantly (p < 0.0001) across different types of indoor kitchen fuel combinations. The geometrical mean (GM) of benzene exposure for cooks during cooking hours in an indoor kitchen using mixed fuel was 75.3 microg/m3 (with partition) and 63.206 microg/m3 (without partition), while the exposure was 11.7 microg/m3 for open type. The benzene exposure was significantly higher (p < 0.05) in an indoor kitchen with respect to open type using mixed fuels. Concentration of benzene (114.1 microg/m3) for cooks in an indoor kitchen with partition using dung fuel was significantly higher in comparison to non-cooks (5.1 microg/m3) for open type. Benzene exposure was not significantly different for kitchen with ventilation (31.2 microg/m3) and without ventilation (45.0 microg/m3) using wood fuel. However, this value was significantly (p < 0.05) lower than in indoor kitchens with or without partition. An almost similar trend was observed for toluene but the difference was statistically non-significant. This study may be helpful in developing a regional exposure database and in the facilitation of health risk assessment due to volatile organic pollutants in our day-to-day environment.     

Improved HPLC method for analysis of 1-hydroxypyrene in human urine specimens of cigarette smokers

A method for the rapid and sensitive analysis of 1-hydroxypyrene in human urine was improved by high performance liquid chromatography (HPLC) with fluorescence detection. The limit of detection decreased approximately threefold when triethylamine was added to the extracts prior to the chromatographic determination. The sensitivity was increased mainly due to triethylamine blockage of the secondary-retention effects. The analysis time was approximately 20 min per run. This method was applied to the analysis of 1-hydroxypyrene in 125 urine specimens collected from cigarette smokers who had non-occupational exposure to polycyclic aromatic hydrocarbons. The average concentrations of urinary 1-hydroxypyrene were 0.04 micromol/mol creatinine in non-smokers, 0.20 micromol/mol creatinine in light smokers, 0.46 micromol/mol creatinine in medium smokers, and 1.16 micromol/mol creatinine in heavy cigarette smokers. The levels of urinary 1-hydroxypyrene correlated strongly with cigarette intake (r2 = 0.93, P < 0.001).     

Gas cooking, kitchen ventilation, and exposure to combustion products

We evaluated a questionnaire-based system for classifying homes into groups with distinctly different chances of accumulating combustion products from cooking appliances. The system was based on questions about type of cooking appliance, type and use of ventilation provisions, and kitchen size. Real-time measurements were made of CO, CO(2), temperature, and water vapor, and passive sampling was performed of nitrogen oxides, over a week-long period in 74 kitchens. During the measurements, inhabitants kept a diary to record appliance use time and use of ventilation provisions. The questionnaire-based and diary-based home classifications for the 'Chance of Accumulation of Combustion Products' (CACP) turned out to agree fairly well. For CO(2) as well as for CO a significant difference between the 'high' and 'low' CACP groups was found for the mean accumulation in the kitchen during cooking of the combustion generated concentrations. These facts are considered to be important experimental evidence of the CACP stratification being valid for our study population. In the homes studied, NO(2) as well as CO concentrations were found to be lower compared with previous studies in The Netherlands. Practical Implications Previous studies on indoor combustion product dispersal conducted in the early- to mid-1980s in the Netherlands showed much higher NO(2) and CO concentrations than the present study. Apparently, the removal of combustion products formed during cooking is more efficient in the (mostly newer) homes that we studied than in the homes studied in the early- to mid-1980s. More detailed knowledge of kitchen situations is needed to improve the CACP model. Future studies can achieve this by using questionnaires on the kitchen situation, diaries and real-time measurements of the combustion products under consideration.     

Particulate exposure and size distribution from wood burning stoves in Costa Rica

Biomass fuel is the most common energy source for cooking and space heating in developing countries. Biomass fuel combustion causes high levels of indoor air pollutants including particulates and other combustion by-products. We measured indoor air quality in 23 houses with a wood burning stove in rural residential areas of Costa Rica. Daily PM2.5, PM10 and CO concentrations, and particle size distribution were simultaneously measured in the kitchen. When a wood burning stove was used during the monitoring period, average daily PM2.5 and PM10 concentrations were 44 and 132 microg/m3, respectively. Average CO concentrations were between 0.5 and 3.3 ppm. All houses had a particle size distribution of either one or two peaks at around 0.7 and 2.5 microm aerodynamic diameters. The particulate levels increased rapidly during cooking and decreased quickly after cooking. The maximum peak particulate levels ranged from 310 to 8170 microg/m3 for PM2.5 and from 500 to 18900 microg/m3 for PM10 in all houses. Although the 24-h particulate levels in this study are lower than the National Ambient Air Quality Standards of PM2.5 and PM10, it is important to note that people, especially women and children, are exposed to extremely high levels of particulates during cooking.     

农居一体化用能新模式的室内热舒适性模拟

为改善农村冬季室内居住环境、充分利用可再生能源,提出了一种基于生物质成型燃料炉的一体化用能模式,该模式将炊事、散热器、水暖床、热水器等集成为一个系统,并利用Airpak模拟软件对比分析新模式供暖相较传统采暖方式供暖效果的改善情况。模拟结果表明:水暖床表面温度分布的均匀性大为提高,并且该系统房间的温度比传统火炕供暖房间的温度高出5℃左右;传统火炕房间的PMV平均值在-1.19左右,而新模式供暖房间的PMV平均值为-0.10;传统火炕房间的PPD平均值为39.8%,而新模式供暖房间的PPD平均值为13.47%。     

The effect of housing characteristics and occupant activities on the respiratory health of women and children in Lao PDR

The paper presents the results of a study conducted into the relationship between dwelling characteristics and occupant activities with the respiratory health of resident women and children in Lao People's Democratic Republic (PDR). Lao is one of the least developed countries in south-east Asia with poor life expectancies and mortality rates. The study, commissioned by the World Health Organisation, included questionnaires delivered to residents of 356 dwellings in nine Districts in Lao PDR over a five month period (December 2005-April 2006), with the aim of identifying the association between respiratory health and indoor air pollution, in particular exposures related to indoor biomass burning. Adjusted odds ratios were calculated for each health outcome separately using binary logistic regression. After adjusting for age, a wide range of symptoms of respiratory illness in women and children aged 1-4 years were positively associated with a range of indoor exposures related to indoor cooking, including exposure to a fire and location of the cooking place. Among women, “dust always inside the house” and smoking were also identified as strong risk factors for respiratory illness. Other strong risk factors for children, after adjusting for age and gender, included dust and drying clothes inside. This analysis confirms the role of indoor air pollution in the burden of disease among women and children in Lao PDR.     

Ultrafine particle concentrations and exposures in seven residences in northern California

Human exposures to ultrafine particles (UFP) are poorly characterized given the potential associated health risks. Residences are important sites of exposure. To characterize residential exposures to UFP in some circumstances and to investigate governing factors, seven single-family houses in California were studied during 2007-2009. During multiday periods, time-resolved particle number concentrations were monitored indoors and outdoors and information was acquired concerning occupancy, source-related activities, and building operation. On average, occupants were home for 70% of their time. The geometric mean time-average residential exposure concentration for 21 study subjects was 14,500 particles per cm(3) (GSD = 1.8; arithmetic mean ± standard deviation = 17,000 ± 10,300 particles per cm(3)). The average contribution to residential exposures from indoor episodic sources was 150% of the contribution from particles of outdoor origin. Unvented natural-gas pilot lights contributed up to 19% to exposure for the two households where present. Episodic indoor source activities, most notably cooking, caused the highest peak exposures and most of the variation in exposure among houses. Owing to the importance of indoor sources and variations in the infiltration factor, residential exposure to UFP cannot be characterized by ambient measurements alone. PRACTICAL IMPLICATIONS: Indoor and outdoor sources each contribute to residential ultrafine particle (UFP) concentrations and exposures. Under the conditions investigated, peak exposure concentrations indoors were associated with cooking, using candles, or the use of a furnace. Active particle removal systems can mitigate exposure by reducing the persistence of particles indoors. Eliminating the use of unvented gas pilot lights on cooking appliances could also be beneficial. The study results indicate that characterization of human exposure to UFP, an air pollutant of emerging public health concern, cannot be accomplished without a good understanding of conditions inside residences.