Experimental exposure to wood-smoke particles in healthy humans: effects on markers of inflammation, coagulation, and lipid peroxidation.

Particulate air pollution is known to increase cardiovascular morbidity and mortality. Proposed mechanisms underlying this increase include effects on inflammation, coagulation factors, and oxidative stress, which could increase the risk of coronary events and atherosclerosis. The aim of this study was to examine whether short-term exposure to wood smoke affects markers of inflammation, blood hemostasis, and lipid peroxidation in healthy humans. Thirteen subjects were exposed to wood smoke and clean air in a chamber during two 4-h sessions, 1 wk apart. The mass concentrations of fine particles at wood smoke exposure were 240-280 mug/m3, and number concentrations were 95,000-180,000/cm3. About half of the particles were ultrafine (< 100 nm). Blood and urine samples were taken before and after the experiment. Exposure to wood smoke increased the levels of serum amyloid A, a cardiovascular risk factor, as well as factor VIII in plasma and the factor VIII/von Willebrand factor ratio, indicating a slight effect on the balance of coagulation factors. Moreover, there was an increased urinary excretion of free 8-iso-prostaglandin2alpha, a major F2-isoprostane, though this was based on nine subjects only, indicating a temporary increase in free radical-mediated lipid peroxidation. Thus, wood-smoke particles at levels that can be found in smoky indoor environments seem to affect inflammation, coagulation, and possibly lipid peroxidation. These factors may be involved in the mechanisms whereby particulate air pollution affects cardiovascular morbidity and mortality. The exposure setup could be used to establish which particle characteristics are critical for the effects.

Experimental wood smoke exposure in humans.

Experimental studies are used to evaluate effects of human exposure to diesel exhaust and concentrated ambient particles. This article describes a system for studying exposure of humans to wood smoke. Wood smoke was generated using a wood stove placed outside an exposure chamber that can hold at least 10 subjects. A partial flow of the generated wood smoke from the stove was mixed with filtered indoor air. Personal and stationary measurements were performed of PM2.5 and PM1 mass concentrations and various volatile organic compounds (VOCs): 1,3-butadiene, benzene, and aldehydes. In addition, particulate matter (PM) mass, number concentrations, and size distributions of particles (0.007-6.7 microm), as well as nitrous oxides, CO2, and CO, were measured online. Filters were analyzed for trace elements and black smoke. Polycyclic aromatic compounds, toluene, and xylenes were determined in stationary samples. Results of the first experiment showed no differences between personal and stationary measurements for particles or VOCs. Consequently, stationary measurements can be used to predict personal exposure. All PM mass (about 250 microg/m3) was in the PM1 fraction. Subjective symptoms were generally weak, while clear objective signs were found, for example, in biomarkers of inflammation. With careful control of the combustion process, relatively constant mass and number concentrations were obtained over each exposure session. By varying the combustion and dilution of the wood smoke, different exposure scenarios can be achieved and thus, knowledge about which of the properties of particles and gaseous compounds are crucial for the effects.

Formaldehyde levels in Sweden: personal exposure, indoor, and outdoor concentrations.

Formaldehyde is a ubiquitous environmental pollutant and is probably carcinogenic to humans. Exposure to formaldehyde was investigated in the general population with personal as well as stationary measurements. The results from two campaigns in two Swedish cities are presented, including measurements of personal exposure among a total of 65 randomly selected subjects together with simultaneous measurements of individual indoor and outdoor concentrations. Diffusive GMD samplers were placed in the breathing zone, in the participants' bedrooms, and outside their homes for 24 h in campaign A and six days in campaign B. Repeated measurements were also conducted in order to study the variability between and within individuals. Median personal exposure to formaldehyde was 22 microg/m(3) (campaign A) and 23 microg/m(3) (campaign B), which is within the guideline value range of 12-60 microg/m(3) proposed in Sweden. Bedroom concentrations were generally slightly higher than personal exposure, while outdoor concentrations (measured only in campaign B) were low. In campaign B, the stationary measurements were used to model personal exposure. Bedroom concentrations were found to explain 90% of the variation of the measured personal exposure and predicted personal exposure nearly as well as an extended model that also included the outdoor contribution. Subjects living in single-family houses had significantly higher exposure to formaldehyde compared with subjects living in apartments. The 24-h and 6-day sampling periods yield a relatively low within-individual variability for formaldehyde measurements with GMD samplers.

Indoor levels of polycyclic aromatic hydrocarbons in homes with or without wood burning for heating.

The aim of this study was to investigate the impact of domestic wood burning on indoor levels of polycyclic aromatic hydrocarbons (PAHs). Indoor and outdoor concentrations of 27 PAHs were measured during wintertime in homes with (n= 13) or without (n 0) wood-burning appliances and at an ambient site in a Swedish residential area where wood burning for space heating is common. Twenty-four hour indoor levels of anthracene, benzo(ghi)fluoranthene, cyclopenta(cd)pyrene, benz(a)anthracene, chrysene/triphenylene, benzo(a)pyrene (BaP), indeno(1,2,3-cd)pyrene, benzo(ghi)perylene, and coronene were significantly (about 3- to 5-fold) higher in homes with, compared with homes without, wood-burning appliances. The outdoor levels of PAHs were generally higher than the indoor levelsfor all PAHs exceptforthe methylated phenanthrenes. The total PAH cancer potency (sum of BaP equivalents) was significantly higher (about 4 times) in the wood-burning homes compared with the reference homes, with BaP being the largest contributor, while phenanthrene made the largest contribution to the total PAH concentration in indoor and outdoor air. The median indoor BaP level in the wood-burning homes (0.52 ng/m3) was 5 times higher than the Swedish health-based guideline of 0.1 ng/m3, which was also exceeded outdoors on all days (median 0.37 ng/m3).

The impact of domestic wood burning on personal, indoor and outdoor levels of 1,3-butadiene, benzene, formaldehyde and acetaldehyde.

The aim of this study was to quantify personal exposure and indoor levels of the suspected or known carcinogenic compounds 1,3-butadiene, benzene, formaldehyde and acetaldehyde in a small Swedish town where wood burning for space heating is common. Subjects (wood burners, n = 14), living in homes with daily use of wood-burning appliances were compared with referents (n = 10) living in the same residential area. Personal exposure and stationary measurements indoors and at an ambient site were performed with diffusive samplers for 24 h. In addition, 7 day measurements of 1,3-butadiene and benzene were performed inside and outside the homes. Wood burners had significantly higher median personal exposure to 1,3-butadiene (0.18 microg m(-3)) compared with referents (0.12 microg m(-3)), which was also reflected in the indoor levels. Significantly higher indoor levels of benzene were found in the wood-burning homes (3.0 microg m(-3)) compared with the reference homes (1.5 microg m(-3)). With regard to aldehydes, median levels obtained from personal and indoor measurements were similar although the four most extreme acetaldehyde levels were all found in wood burners. High correlations were found between personal and indoor levels for all substances (r(s) > 0.8). In a linear regression model, type of wood-burning appliance, burning time and number of wood replenishments were significant factors for indoor levels of 1,3-butadiene. Domestic wood burning seems to increase personal exposure to 1,3-butadiene as well as indoor levels of 1,3-butadiene and benzene and possibly also acetaldehyde. The cancer risk from these compounds at exposure to wood smoke is, however, estimated to be low in developed countries.

Exposure to fine particles (PM2.5 and PM1) and black smoke in the general population: personal, indoor, and outdoor levels.

Personal exposure to PM(2.5) and PM(1), together with indoor and residential outdoor levels, was measured in the general adult population (30 subjects, 23-51 years of age) of Gothenburg, Sweden. Simultaneously, urban background concentrations of PM(2.5) were monitored with an EPA WINS impactor. The 24-h samples were gravimetrically analyzed for mass concentration and black smoke (BS) using a smokestain reflectometer. Median levels of PM(2.5) were 8.4 microg/m(3) (personal), 8.6 microg/m(3) (indoor), 6.4 microg/m(3) (residential outdoor), and 5.6 microg/m(3) (urban background). Personal exposure to PM(1) was 5.4 microg/m(3), while PM(1) indoor and outdoor levels were 6.2 and 5.2 microg/m(3), respectively. In non-smokers, personal exposure to PM(2.5) was significantly higher than were residential outdoor levels. BS absorption coefficients were fairly similar for all microenvironments (0.4-0.5 10(-5) m(-1)). Personal exposure to particulate matter (PM) and BS was well correlated with indoor levels, and there was an acceptable agreement between personal exposure and urban background concentrations for PM(2.5) and BS(2.5) (r(s)=0.61 and 0.65, respectively). PM(1) made up a considerable amount (70-80%) of PM(2.5) in all microenvironments. Levels of BS were higher outdoors than indoors and higher during the fall compared with spring. The correlations between particle mass and BS for both PM(2.5) vs. BS(2.5) and PM(1) versus BS(1) were weak for all microenvironments including personal exposure. The urban background station provided a good estimate of residential outdoor levels of PM(2.5) and BS(2.5) within the city (r(s)=0.90 and 0.77, respectively). Outdoor levels were considerably affected by long-range transported air pollution, which was not found for personal exposure or indoor levels. The within-individual (day-to-day) variability dominated for personal exposure to both PM(2.5) and BS(2.5) in non-smokers.

The use of semipermeable membrane devices as passive samplers to determine persistent organic compounds in indoor air.

In the study reported here semipermeable membrane devices (SPMDs) were used to sample 28 PAHs and 19 PCBs in the gas phase in 15 single-family houses located in an area where domestic wood burning is widespread. Eight of the households used wood burning appliances whereas the others used other systems for residential heating. Most of the studied compounds were found in the houses: the PAHs at levels that were similar to or slightly higher than published SPMD-sampled levels for background or urban sites in Sweden, and the PCBs at levels that were somewhat lower than those recently found in both indoor and outdoor urban locations. A principal component analysis revealed that wood-burning heating systems may contribute to PAHs in indoor air. The sources may be emissions indoors or penetration from outdoors. The convenience of SPMD technology facilitates its use for semi-quantitative screening and monitoring of various persistent organic compounds indoors in dwellings and working environments.