Indoor Exposure Levels Research Articles

Inverse association between endotoxin exposure and canine atopic dermatitis

The development of canine atopic dermatitis (CAD) may be related to exposure to mite allergens, bacterial endotoxin and/or fungal glucans. In this study, indoor exposure levels of house dust mite allergens, endotoxins and fungal glucans were measured to determine their possible association with CAD. A case-control study including adult Labrador retrievers with (n=28) and without (controls; n=65) CAD was conducted. Dust samples were collected from the living room floor and the bedding and coat of the dog and these were analyzed for house dust mite allergens Der p1 and Der f1, endotoxin and (1→3)-β-d-glucan levels. Dog owners were also required to return a questionnaire regarding their home characteristics. The endotoxin exposure level in the coats of dogs was significantly inversely associated with CAD (odds ratio 0.38; 95% confidence interval 0.15-0.97; P<0.05). No significant difference was found in exposure levels to house dust mite allergens and fungal glucans. The results indicated that endotoxin exposure is inversely associated with CAD, suggesting a protective effect of high indoor endotoxin exposure towards the development of the condition.

Scoping indoor airborne fungi in an excellent indoor air quality office building in Hong Kong

This study aims to investigate the differences in indoor airborne fungal exposure between a selective subset of air-conditioned offices within a building classified with excellent indoor air quality (IAQ) in Hong Kong and typical offices in Hong Kong and other countries. Assessments of the indoor and outdoor fungal exposure levels and compositions, and indoor-to-outdoor (I/O) fungi count ratios were conducted in 82 offices of a building with excellent IAQ. The indoor airborne fungi were detected in 97.6% air samples with airborne fungi count (AFC) ranged from 2 to 92 CFU m—3, and with a mean I/O ratio of 0.5. It was reported that the indoor AFC was significantly lower than other typical offices in Hong Kong and other countries. Aspergillus, Cladosporium, Penicillium and yeast were dominant indoors but an outdoor dominant fungi Alternaria was not detected in the offices. This study reveals that better control of thermal conditions and proper maintenance of the air-conditioning system would lower the AFC. In addition, a significantly higher relative abundance (RA) of Aspergillus and lower RA of Cladosporium were also reported. It presents a useful reference for IAQ assessment regarding the quantification of airborne fungal exposure in air-conditioned offices in a building with excellent IAQ. Practical application: An assessment of exposure levels to common indoor airborne fungi, such as Aspergillus, Cladosporium, Penicillium and yeast in Hong Kong air-conditioned offices reveals that an excellent office environment with good thermal and IAQ control would associate with a significantly lower airborne fungi count. A significant different pattern of indoor airborne fungi were observed that a significantly higher relative abundance of Aspergillus and lower relative abundance of Cladosporium were reported.

Exposure assessment and risk characterisation for consumers associated to the use of electrical diffuser for insecticides

Insecticides are mainly used in the home environment, and most of them are recognised to pose risks for the human health. In particular, pyrethroids are an insecticide category widely used in agriculture and households, and for industrial purposes to get protection from mosquitoes, cockroaches and other insects. In this study, both exposure and risk following the application of insecticides by using an electrical heating device have been characterised. The indoor exposure levels have been estimated by using ConsExpo Model. The exposure values have been compared with the toxicological data from the WHO Specifications. Thus, the risks have been estimated by calculating the Derived No-Effect Level (DNEL) and the risks result to be very low. However, a potential risk might occur at the beginning of the exposure. Therefore, possible risk reduction measures should be put in place, such as avoiding people to stay while the electrical heating device is functioning.

Effects of exposure measurement error in the analysis of health effects from traffic-related air pollution

In large epidemiological studies, many researchers use surrogates of air pollution exposure such as geographic information system (GIS)-based characterizations of traffic or simple housing characteristics. It is important to evaluate quantitatively these surrogates against measured pollutant concentrations to determine how their use affects the interpretation of epidemiological study results. In this study, we quantified the implications of using exposure models derived from validation studies, and other alternative surrogate models with varying amounts of measurement error on epidemiological study findings. We compared previously developed multiple regression models characterizing residential indoor nitrogen dioxide (NO(2)), fine particulate matter (PM(2.5)), and elemental carbon (EC) concentrations to models with less explanatory power that may be applied in the absence of validation studies. We constructed a hypothetical epidemiological study, under a range of odds ratios, and determined the bias and uncertainty caused by the use of various exposure models predicting residential indoor exposure levels. Our simulations illustrated that exposure models with fairly modest R(2) (0.3 to 0.4 for the previously developed multiple regression models for PM(2.5) and NO(2)) yielded substantial improvements in epidemiological study performance, relative to the application of regression models created in the absence of validation studies or poorer-performing validation study models (e.g., EC). In many studies, models based on validation data may not be possible, so it may be necessary to use a surrogate model with more measurement error. This analysis provides a technique to quantify the implications of applying various exposure models with different degrees of measurement error in epidemiological research.

Particulate matter and gaseous pollutants in residences in Antwerp, Belgium

This comprehensive study, a first in Flanders, Belgium, aimed at characterizing the residential indoor air quality of subgroups that took part in the European Community Respiratory Health Survey (ECRHS I—1991 and ECHRS II—1996) questionnaire-based asthma and related illnesses studies. This pilot study aimed at the evaluation of particulate matter and various inorganic gaseous compounds in residences in Antwerp. In addition personal exposure to the gaseous compounds of one individual per residence was assessed. The main objective was to obtain some base-line pollutant levels and compare these with studies performed in other cities, to estimate the indoor air quality in residences in Antwerp. Correlations between the various pollutant levels, indoor:outdoor ratios and the micro-environments of each residence were investigated. This paper presents results on indoor and ambient PM 1, PM 2.5 and PM 10 mass concentrations, its elemental composition in terms of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb, Al, Si, S and Cl and the water-soluble ionic concentrations in terms of SO 4 2−, NO 3 2−, Cl −, NH 4 + K +, Ca 2+. In addition, indoor, ambient and personal exposure levels of the gases NO 2, SO 2, and O 3 were determined. Elevated indoor:outdoor ratios were found for NO 2 in residences containing gas stoves. In smoker's houses increased PM concentrations of 58 and 43% were found for the fine and coarse fractions respectively. Contrary to the fact that all I/O ratios of the registered elements in each individual house were significantly correlated to each other, no correlation could be established between the I/O ratios of the different houses, thus indicating a unique micro-environment for each residence. Linear relationships between the particulate matter elemental composition, SO 2 and O 3 levels indoors and outdoors could be established. No linear relationships between indoor and outdoor NO 2 and particulate mass concentrations were found.

Plenary Lectures

Traffic emissions are an important contributor to ambient air pollution, especially in large cities featuring extensive and high density traffic networks. Bus fleets represent a significant part of inner city traffic causing an increase in exposure to general public, passengers and drivers along bus routes and at bus stations. Limited information is available on quantification of the levels, and governing parameters affecting the air pollution exposure at bus stations. The presented study investigated the bus emissions-dominated ambient air in a large, inner city bus station, with a specific focus on submicrometer particles. The study’s objectives were (i) quantification of the concentration levels; (ii) characterisation of the spatio-temporal variation; (iii) identification of the parameters governing the emissions levels at the bus station and (iv) assessment of the relationship between particle concentrations measured at the street level (background) and within the bus station. The results show that up to 90% of the emissions at the station are ultrafine particles (smaller than 100 nm), with the concentration levels up to 10 times the value of urban ambient air background (annual) and up to 4 times the local ambient air background. The governing parameters affecting particle concentration at the station were bus flow rate and meteorological conditions (wind velocity). Particle concentration followed a diurnal trend, with an increase in the morning and evening, associated with traffic rush hours. Passengers’ exposure could be significant compared to the average outdoor and indoor exposure levels.

Distribution of 2,4-D in air and on surfaces inside residences after lawn applications: comparing exposure estimates from various media for young children.

We collected indoor air, surface wipes (floors, table tops, and window sills), and floor dust samples at multiple locations within 11 occupied and two unoccupied homes both before and after lawn application of the herbicide 2,4-D. We measured residues 1 week before and after application. We used collected samples to determine transport routes of 2,4-D from the lawn into the homes, its subsequent distribution between the indoor surfaces, and air concentration as a function of airborne particle size. We used residue measurements to estimate potential exposures within these homes. After lawn application, 2,4-D was detected in indoor air and on all surfaces throughout all homes. Track-in by an active dog and by the homeowner applicator were the most significant factors for intrusion. Resuspension of floor dust was the major source of 2,4-D in indoor air, with highest levels of 2,4-D found in the particle size range of 2.5-10 microm. Resuspended floor dust was also a major source of 2,4-D on tables and window sills. Estimated postapplication indoor exposure levels for young children from nondietary ingestion may be 1-10 microg/day from contact with floors, and 0.2-30 microg/day from contact with table tops. These are estimated to be about 10 times higher than the preapplication exposures. By comparison, dietary ingestion of 2,4-D is approximately 1.3 microg/day.

Distribution of 2,4-D in Air and on Surfaces inside Residences after Lawn Applications: Comparing Exposure Estimates from Various Media for Young Children

We collected indoor air, surface wipes (floors, table tops, and window sills), and floor dust samples at multiple locations within 11 occupied and two unoccupied homes both before and after lawn application of the herbicide 2,4-D. We measured residues 1 week before and after application. We used collected samples to determine transport routes of 2,4-D from the lawn into the homes, its subsequent distribution between the indoor surfaces, and air concentration as a function of airborne particle size. We used residue measurements to estimate potential exposures within these homes. After lawn application, 2,4-D was detected in indoor air and on all surfaces throughout all homes. Track-in by an active dog and by the homeowner applicator were the most significant factors for intrusion. Resuspension of floor dust was the major source of 2,4-D in indoor air, with highest levels of 2,4-D found in the particle size range of 2.5-10 microm. Resuspended floor dust was also a major source of 2,4-D on tables and window sills. Estimated postapplication indoor exposure levels for young children from nondietary ingestion may be 1-10 microg/day from contact with floors, and 0.2-30 microg/day from contact with table tops. These are estimated to be about 10 times higher than the preapplication exposures. By comparison, dietary ingestion of 2,4-D is approximately 1.3 microg/day.

Indoor behavior and risk assessment following space spraying of d-tetramethrin and d-resmethrin.

To clarify the indoor behavior of insecticides in space spraying, an aerosol canister (containing a mixture of 0.45 g d-tetramethrin and 0.06 g d-resmethrin in a 300-mL product) was applied to a typical Japanese room under various conditions and temporal concentrations in air; floor, walls, and ceiling were monitored. Air concentrations were chiefly dependent on ventilation rates but not on air circulation by an air conditioner. During a periodic spraying, the airborne insecticides did not accumulate in the room, but the floor residues gradually increased with the number of sprayings. After cessation of spraying, however, dislodgeable residues on the floor decreased with time. The time-dependent behavior of d-tetramethrin was simulated by a mathematical model (InPest) developed by the authors, and it was found that the estimated values agreed fully with actually measured values. The simulation model also clarified the amount of insecticide evaporated from the room material, the amount vented to the outdoors, and so on. Indoor exposure levels of d-tetramethrin and d-resmethrin to the room's occupants were estimated with the monitored concentrations when a 10-sec spraying was done twice a day for 30 days. The margins of safety, which were obtained by dividing the no observed effect levels by the exposure levels, were over 100 for unclothed occupants, even in the room with the windows closed.

Indoor behavior and risk assessment following residual spraying of d-phenothrin and d-tetramethrin.

To clarify the indoor behavior of insecticides in residual spraying equivalent to a crack and crevice treatment, an aerosol canister (containing a mixture of 0.9 g d-phenothrin and 1.1 g d-tetramethrin in a 300-mL product) was applied to a typical Japanese room under various conditions, and temporal concentrations in air and on the floor, walls, and ceiling were monitored. Air concentrations were chiefly dependent on ventilation rates but not on air circulation. During a periodic spraying, the airborne insecticides did not accumulate in the room, but the floor residues gradually increased with the number of sprayings. After cessation of spraying, however, dislodgeable residues on the floor decreased with time. The time-dependent behavior of d-phenothrin was simulated by a developed simulation model (InPest), which helped a more comprehensive understanding of the insecticide behavior. Indoor exposure levels of d-phenothrin and d-tetramethrin to room occupants were estimated with the monitored concentrations when a 2.5-min spraying was done four times over an 8-week period. The margins of safety, which were obtained by dividing the no observed effect levels by the exposure levels, were over 100 for unclothed occupants, even in a room with the windows closed.

Paying for Safety: Voluntary Reduction of Residential Radon Risks

identify radon as a public health problem, to sponsor widespread testing, and to develop reliable, low-cost techniques for reducing indoor exposure levels. Data recently collected in Sweden make it possible to derive the first empirical estimates of homeowner willingness to pay to reduce radon health risks. This paper reports these estimates and discusses their implication for public policy. We conclude that the low value of estimated willingness to pay indicates that homeowners may have interpreted the technology-based recommended exposure as a safety threshold. After reviewing the nature and regulatory history of the radon hazard, we present a theoretical framework for modeling the value of reduced radon risk. The model employs a conventional state-dependent utility function associated with a discrete decision to mitigate or not to mitigate. In subsequent sections we describe the data collected from a sample of homeowners participating in a health department testing program and report parameter estimates from a binomial logit analysis. The estimated parameters form the basis for calculations of the probability of mitigating and willingness to pay for mitigation at various exposure levels and for various household characteristics.

Airborne Aspergillus fumigatus levels outside and within a large clinical center

Most considerations of Aspergillus fumigatus prevalence have implied that patterns of occurrence observed within London hospitals are generally applicable. Since prevalence data are almost nonexistent elsewhere, this assumption remains untested. To provide a comparison relevant to North America, we have monitored thermotolerant fungi outside as well as at two sites within the University Hospital, Ann Arbor, Michigan, during one year. Collections were made with paired Andersen samplers and malt agarfor 30- to 40-min periods in a hallway adjacent to 6W, a general medical ward (47 days), and 2W, a lower level service and supply area (40 days); in addition, 10-min outdoor samples (44 days) were taken on an unobstructed hospital rooftop (out). Recoveries were analyzed after 3 and 7 days of 37 °C aerobic incubation. Virtually complete suppression of Cladosporium form species at 37 ° left a mycoflora with A. fumigatus, A. niger, Paecilomyces spp., Mucor spp., and yeast/bacteria predominating. Although the proportions of samples yielding A. fumigatus were 76% for 6W, 57% for 2W, and 56% (out), levels exceeded 40 isolates/m 3 only twice and were over 10 isolates/m 3 on only 10 of 131 total samples. For 6W, 2W and out, respectively, means were 4.78, 1.97, and 6.25 isolates/m 3; medians were 1.20, 1.05 and 1.75/m 3 without annual trends indoors and with only a limited outdoor summer increase. Our data fail entirely to show the fall-winter abundance observed in the London report and suggest substantially lower indoor exposure levels of A. fumigatus than those noted in London.