Occupational exposure to formaldehyde in an institute of morphology in Brazil: a comparison of area and personal sampling

Background, aims, and scope

Formaldehyde (FA) is a harmful chemical, which is classified as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer. Solutions of FA that are used to preserve cadavers in research and education morphological institutes represent a risk to occupational health of professionals and students. During the dissection of cadavers in the anatomy laboratories, FA vapors are emitted, resulting in the exposure of students and their instructors to elevated levels of FA. The World Health Organization recommends an air quality guideline value of 0.1 mg m^?3 for exposure to FA. The limit of occupational exposure adopted by the Brazilian legislation (2.3 mg m^?3) is markedly higher than those adopted by institutions of other countries around the world. The purpose of this study was to determine the levels of personal exposure and the area concentration of FA in the morphology department of the Federal Fluminense University, Brazil, and investigate and compare the relationship between them.

Methods

Four rooms distributed in the three floors of the Morphology Department were evaluated: the embalming laboratory, the anatomy laboratories, the corridor of the teachers?? rooms, and the entrance hall. Thirty-six samples in total were collected in the second semester of 2010 and first semester of 2011. The air sampling and FA analysis were performed according to the EPA TO-11A Protocol, using a diffusive sampling device for carbonyl compounds. Personal samples were collected from monitors using a sampling device pinned on each person??s lapel. The samples were analyzed using rapid resolution liquid chromatography with UV-DAD detection at 360 nm.

Results and discussion

The concentrations of FA ranged from 0.20 and 0.18 mg m^?3 in the corridor between the teachers?? rooms, 0.03 to 0.37 mg m^?3 in the entrance hall, 0.22 to 2.07 mg m^?3 in the anatomy laboratory, 2.21 to 2.52 mg m^?3, in the embalming room. The levels found in the corridor between the teachers?? rooms and in the entrance hall were lower than in other compartments because of their large distances to the sources of FA and better ventilation. The other rooms presented higher levels of FA because of the activities carried there (embalming and dissection procedures). Even in the rooms that showed the lowest levels of FA, the values found were higher than those established by all international guideline limits, except the Brazilian legislation limit, although, the concentration level in the embalming room was even greater than the Brazilian guideline. These concentrations are 100?C1,000-fold higher than those reported in an FA outdoor study. The exposure levels of monitors and students ranged from 1.89 to 4.82 mg m^?3, indicating that current practices at the Morphology Department at the university would represent a health risk. The simultaneous monitoring of area concentrations and personal exposure showed that the characteristics of classes and of cadavers?? parts, the number of students in the room and even the activities of the monitors influence the FA concentrations.

Conclusion

This study revealed that the concentration of FA was low in the ventilated areas of the Morphology Department, and that the personal exposure when the person was close to the cadavers during the dissection procedure was higher than the mean FA concentration. This should be considered in the risk assessment of FA during these activities without effective protection equipment. It is suggested that the Brazilian legislation of exposure to formaldehyde requires an urgent update considering international legislation.     

Exposure of population and microenvironmental distributions of volatile organic compound concentrations in the EXPOLIS study

Determination of volatile organic compounds (VOCs) formed one part of the EU-EXPOLIS project in which the exposure of European urban populations to particles and gaseous pollutants was studied. The EXPOLIS study concentrated on 30 target VOCs selected on the basis of environmental and health significance and usability of the compounds as markers of pollution sources. In the project, 201 subjects in Helsinki, 50 in Athens, 50 in Basel, 50 in Milan and, 50 in Oxford and 50 in Prague were selected for the final exposure sample. The microenvironmental and personal exposure concentrations of VOCs were the lowest in Helsinki and Basel, while the highest concentrations were measured in Athens and Milan; Oxford and Prague were in between. In all cities, home indoor air was the most significant exposure agent. Workplace indoor air concentrations measured in this study were generally lower than the home indoor concentrations and home outdoor air played a minor role as an exposure agent. When estimating the measured personal exposure concentrations using the measured concentrations and time fractions spent at home indoors, at home outdoors, and at the workplace, it could be concluded that these three microenvironments do not fully explain the personal exposure. Other important sources for personal exposure must be encountered, the most important being traffic/transportation and other indoor environments not measured in this study.     

Personal exposure of graduate students attending the college of natural sciences or social sciences to volatile organic compounds on campus

The present study measured the levels of 24 selected volatile organic compounds (VOCs) in the personal air samples obtained from graduate students attending the college of natural sciences (GSNSs) or social science (GSSSs) during their daily activities on campus along with associated indoor and outdoor air samples. In addition, the sources of their personal exposure were characterized using multivariate statistical models. In the personal samples of GSNSs and GSSSs, 16 and 15 different VOCs were always detected, respectively. The personal exposure of five chlorinated hydrocarbons and six aromatics was significantly higher for GSNSs than for GSSSs. Consistently, the indoor levels of these compounds were higher for GSNSs (in research and laboratory rooms) than for GSSSs (in research rooms). However, the personal exposure of two aromatic VOCs (1,2,4- and 1,3,5-trimethylbenzene) was higher for GSSSs. Moreover, the personal exposure of the five chlorinated and six aromatic compounds was significantly correlated with VOC concentrations both in the research and laboratory rooms of GSNSs and with those in the research rooms of GSSSs. For certain VOCs, outdoor sources were also a major contributor to the personal exposure of both GSNSs and GSSSs. The multivariate models identified five factors that accounted for 81% of the total variance and four factors that explained 76% of the total variance. It was further suggested that multiple indoor sources in research rooms such as office equipment, building finishing materials, and air fresheners were the main source for the personal exposure to VOCs for GSNSs, whereas building finishing materials were the main source for GSSSs.     

Exposure to carbonyl compounds in charcoal production plants in Bahia, Brazil

Studies have investigated the exposure levels of carbonyl compounds (CC) in the indoor and outdoor air of homes, vehicles, workplaces, urban and industrial areas, and rural sites. However, an investigation of these emissions and occupational exposure to CC in charcoal production facilities has not been previously conducted. The objective of this study was to measure the atmospheric concentrations of several CC to assess the exposure of workers of two charcoal plants located north of Salvador, Bahia, Brazil. Stationary and personal samples were collected using Sep-Pak® C18 cartridges that were coated with a 0.2 % acidic solution of 2,4-dinitrophenylhydrazine. The quantification of the resulting 2,4-dinitrophenylhydrazone derivatives was conducted using a high-performance liquid chromatography system with UV detection. In the personal samples, the concentrations of formaldehyde, acetaldehyde, propanone, furfural, and C4 isomers (n-butanal-isobutanal-butanone) ranged from 12 to 139, 38 to 165, 136 to 483, 39 to 114, and 63 to 132 μg?m^?3, respectively. In the stationary samples, the concentrations of these CC ranged from 20 to 160, 111 to 284, 328 to 644, 70 to 163, and 100 to 176 μg?m^?3, respectively. When compared to the occupational exposure limits for 8 h, the concentrations of formaldehyde were often greater than the levels recommended by the American National Institute for Occupational Safety and Health, which indicates a health risk for charcoal workers. These results are the first reported concerning the occupational exposure to CC in charcoal plants.     

Evaluation of hazardous airborne carbonyls on a university campus in southern China

A comprehensive assessment of indoor carbonyl compounds for the academic staff, workers, and students was conducted on a university campus in Xiamen, China. A total of 15 representative environment categories, including 12 indoor workplaces and three residential units, were selected. The potential indoor pollution sources were identified based on the variability in the molar compositions and correlation analyses for the target carbonyls. Furnishing materials, cooking emissions, and electronic equipment, such as photocopiers, can generate various carbonyls in the workplace. Comparison studies were conducted in the clerical offices, demonstrating that off-gases from wooden furniture and lacquer coatings, environmental tobacco smoke (ETS), and the use of cleaning reagents elevated the indoor carbonyl levels. The measured concentrations of formaldehyde and acetaldehyde in most locations surpassed the exposure limit levels. The lifetime cancer hazard risk (R) associated with formaldehyde was above the concern risk level (1 × 10^?6) in all of the workplaces. The results indicate that formaldehyde exposure is a valid occupational health and safety concern. Wooden furniture and refurbishing materials can pose serious health threats to occupants. The information in this study could act as a basis for future indoor air quality monitoring in Mainland China.

Implications:A university campus represents a microscale city environment consisting of all the working, living, and commercial needs of staff and students. The scope of this investigation covers 21 hazardous carbonyl species based on samples collected from 15 categories of workplaces and residential building in a university campus in southern China. Findings of the study provide a comprehensive assessment of indoor air quality with regards to workers’ health and safety. No similar study has been carried out in China.     

Source investigation of personal particulates in relation to identify major routes of exposure among urban residentials

Multiple 24-h average outdoor, indoor and personal respirable particulate matter (RPM) measurements were made in different urban residential colonies to determine major routes of personal exposure. The study area was Bhilai-Durg, District Durg, Chhattisgarh, India. About 100 residentials from each of two selected colonies have been surveyed for consent to participate in the study and for preparation of time–activity diary. On the basis of their time–activity diary, residentials have been categorized into three types: type-A, purely residential; type-B, residents who go out, and type-C, residence who go into work, specially in industrial area. A total of 28 adult participants (14 males and 14 females; mean age 40±15, range 21–61 years) were selected and monitored longitudinally during the summer (15 March–15 June) of 2004. Participants’ residential indoor RPM level and also local ambient outdoor RPM levels were measured,and these are done simultaneous with personal monitoring. Residential indoor and ambient outdoors RPM monitoring sessions were throughout the year to obtain infiltration factor more precisely. To compare RPM levels with Indian National Ambient Air Quality Standards (NAAQS) of PM₁₀, simultaneous measurements of PM₁₀ were also done with the course of ambient outdoor RPM monitoring. RPM levels in indoors were higher compared to ambient outdoors. The annual average ratio RPM/PM₁₀ was found to vary significantly among residential sites due to variation in surroundings. Source contribution estimates (SCE) of personal exposure to RPM in selected 12 residences (six from each colony) have been investigated using chemical mass balance model CMB8. Ambient outdoors, residential indoors, soils and road-traffic borne RPM were identified as main routes and principal sources of personal RPM. Results of model output have shown that residential indoors and soil-borne RPM are the major routes of personal exposure.     

Personal carbon monoxide exposure in five European cities and its determinants

Studies involving carbon monoxide (CO) exposure assessment are mainly based on measurements at outdoor fixed sites or in various indoor micro-environments. Few studies have been based on personal exposure measurements. In this paper, we report results on personal measurements of CO in five European cities and we investigate determinants which may influence this personal exposure.Within the multi-centre European EXPOLIS study, personal exposure to CO, measured every minute for 48 h, of 401 randomly selected study participants (mainly non-smokers) was monitored in Athens, Basle, Helsinki, Milan and Prague. Each participant also completed a time-microenvironment-activity diary and an extended questionnaire. In addition, for the same time period, ambient levels of CO from fixed site stations were collected.There are significant differences in both personal exposure and ambient levels within the five cities, ranging from high values in Milan and Athens to low in Helsinki. Ambient levels are a significant correlate and determinant of CO 48-h personal exposure in all cities. From the other determinants studied (time spent in street traffic, time of exposure to ETS and time of exposure to gas burning devices) none was consistently significant for all cities. Change of the ambient CO levels from the 25th to the 75th percentile of its distribution resulted in a 1.5–2 fold increase of 48-h personal exposure. Short time personal exposure was also studied in order to assess the influence of specific sources. Exposure levels were significantly higher when participants were in street traffic and in indoor locations in the presence of smokers.Personal 48-h exposure of non-smokers to CO varies among urban populations depending primarily on the ambient levels. For a CO source to be a significant determinant of the personal 48-h CO exposure, it has to affect the levels of CO in the person's proximity for an adequate length of time. Activities of individuals affect shorter term personal exposure.     

Outdoor/Indoor/Personal ozone exposures of children in Nashville, Tennessee

An ozone (O3) exposure study was conducted in Nashville, TN, using passive O3 samplers to measure six weekly outdoor, indoor, and personal O3 exposure estimates for a group of 10- to 12-yr-old elementary school children. Thirty-six children from two Nashville area communities (Inglewood and Hendersonville) participated in the O3 sampling program, and 99 children provided additional time-activity information by telephone interview. By design, this study coincided with the 1994 Nashville/Middle Tennessee Ozone Study conducted by the Southern Oxidants Study, which provided enhanced continuous ambient O3 monitoring across the Nashville area. Passive sampling estimated weekly average outdoor O3 concentrations from 0.011 to 0.O30 ppm in the urban Inglewood community and from 0.015 to 0.042 ppm in suburban Hendersonville. The maximum 1- and 8-hr ambient concentrations encountered at the Hendersonville continuous monitor exceeded the levels of the 1- and 8-hr metrics for the O3 National Ambient Air Quality Standard. Weekly average personal O3 exposures ranged from 0.0013 to 0.0064 ppm (7-31% of outdoor levels). Personal O3 exposures reflected the proportional amount of time spent in indoor and outdoor environments. Air-conditioned homes displayed very low indoor O3 concentrations, and homes using open windows and fans for ventilation displayed much higher concentrations.     

Personal Exposure to Fine Particulate Matter in Elderly Subjects: Relation between Personal,Indoor, and Outdoor Concentrations

ABSTRACT

The time-series correlation between ambient levels, indoor levels, and personal exposure to PM_2.5 was assessed in panels of elderly subjects with cardiovascular disease in Amsterdam, the Netherlands, and Helsinki, Finland. Subjects were followed for 6 months with biweekly clinical visits. Each subject's indoor and personal exposure to PM_2.5 was measured biweekly, during the 24-hr period preceding the clinical visits. Outdoor PM_2.5 concentrations were measured at fixed sites. The absorption coefficients of all PM_2.5 filters were measured as a marker for elemental carbon (EC). Regression analyses were conducted for each subject separately, and the distribution of the individual regression and correlation coefficients was investigated. Personal, indoor, and ambient concentrations were highly correlated within subjects over time. Median Pearson's R between personal and outdoor PM_2.5 was 0.79 in Amsterdam and 0.76 in Helsinki. For absorption, these values were 0.93 and 0.81 for Amsterdam and Helsinki, respectively. The findings of this study provide further support for using fixed-site measurements as a measure of exposure to PM_2.5 in epidemiological time-series studies.     

Parameter Evaluation and Model Validation of Ozone Exposure Assessment Using Harvard Southern California Chronic Ozone Exposure Study Data

Abstract

To examine factors influencing long‐term ozone (O₃) exposures by children living in urban communities, the authors analyzed longitudinal data on personal, indoor, and outdoor O₃ concentrations, as well as related housing and other questionnaire information collected in the one‐year‐long Harvard Southern California Chronic Ozone Exposure Study. Of 224 children contained in the original data set, 160 children were found to have longitudinal measurements of O₃ concentrations in at least six months of 12 months of the study period. Data for these children were randomly split into two equal sets: one for model development and the other for model validation. Mixed models with various variance‐covariance structures were developed to evaluate statistically important predictors for chronic personal ozone exposures. Model predictions were then validated against the field measurements using an empirical best‐linear unbiased prediction technique.The results of model fitting showed that the most important predictors for personal ozone exposure include indoor O₃ concentration, central ambient O₃ concentration, outdoor O₃ concentration, season, gender, outdoor time, house fan usage, and the presence of a gas range in the house. Hierarchical models of personal O₃ concentrations indicate the following levels of explanatory power for each of the predictive models: indoor and outdoor O₃ concentrations plus questionnaire variables, central and indoor O₃ concentrations plus questionnaire variables, indoor O₃ concentrations plus questionnaire variables, central O₃ concentrations plus questionnaire variables, and questionnaire data alone on time activity and housing characteristics. These results provide important information on key predictors of chronic human exposures to ambient O₃ for children and offer insights into how to reliably and cost‐effectively predict personal O₃ exposures in the future. Furthermore, the techniques and findings derived from this study also have strong implications for selecting the most reliable and cost‐effective exposure study design and modeling approaches for other ambient pollutants, such as fine particulate matter and selected urban air toxics.     

Exposure assessment of air pollutants: a review on spatial heterogeneity and indoor/outdoor/personal exposure to suspended particulate matter,nitrogen dioxide and ozone

This review describes databases of small-scale spatial variations and indoor, outdoor and personal measurements of air pollutants with the main focus on suspended particulate matter, and to a lesser extent, nitrogen dioxide and photochemical pollutants. The basic definitions and concepts of an exposure measurement are introduced as well as some study design considerations and implications of imprecise exposure measurements. Suspended particulate matter is complex with respect to particle size distributions, the chemical composition and its sources. With respect to small-scale spatial variations in urban areas, largest variations occur in the ultrafine (<0.1 μm) and the coarse mode (PM_10–2.5, resuspended dust). Secondary aerosols which contribute to the accumulation mode (0.1–2 μm) show quite homogenous spatial distribution. In general, small-scale spatial variations of PM_2.5 were described to be smaller than the spatial variations of PM₁₀. Recent studies in outdoor air show that ultrafine particle number counts have large spatial variations and that they are not well correlated to mass data. Sources of indoor particles are from outdoors and some specific indoor sources such as smoking and cooking for fine particles or moving of people (resuspension of dust) for coarse particles. The relationships between indoor, outdoor and personal levels are complex. The finer the particle size, the better becomes the correlation between indoor, outdoor and personal levels. Furthermore, correlations between these parameters are better in longitudinal analyses than in cross-sectional analyses. For NO₂ and O₃, the air chemistry is important. Both have considerable small-scale spatial variations within urban areas. In the absence of indoor sources such as gas appliances, NO₂ indoor/outdoor relationships are strong. For ozone, indoor levels are quite small. The study hypothesis largely determines the choice of a specific concept in exposure assessment, i.e. whether personal sampling is needed or if ambient monitoring is sufficient. Careful evaluation of the validity and improvements in precision of an exposure measure reduce error in the measurements and bias in the exposure–effect relationship.     

Personal exposure levels and microenvironmental concentrations of formaldehyde and acetaldehyde in the Helsinki metropolitan area, Finland

Personal 48-hr exposures to formaldehyde and acetaldehyde of 15 randomly selected participants were measured during the summer/autumn of 1997 using Sep-Pak DNPH-Silica cartridges as a part of the EXPOLIS study in Helsinki, Finland. In addition to personal exposures, simultaneous measurements of microenvironmental concentrations were conducted at each participant's residence (indoor and outdoor) and workplace. Mean personal exposure levels were 21.4 ppb for formaldehyde and 7.9 ppb for acetaldehyde. Personal exposures were systematically lower than indoor residential concentrations for both compounds, and ambient air concentrations were lower than both indoor residential concentrations and personal exposure levels. Mean workplace concentrations of both compounds were lower than mean indoor residential concentrations. Correlation between personal exposures and indoor residential concentrations was statistically significant for both compounds. This indicated that indoor residential concentrations of formaldehyde and acetaldehyde are a better estimate of personal exposures than are concentrations in ambient air. In addition, a time-weighted exposure model did not improve the estimation of personal exposures above that obtained using indoor residential concentrations as a surrogate for personal exposures. Correlation between formaldehyde and acetaldehyde was statistically significant in outdoor microenvironments, suggesting that both compounds have similar sources and sinks in ambient urban air.     

Parameter evaluation and model validation of ozone exposure assessment using Harvard Southern California Chronic Ozone Exposure Study data

To examine factors influencing long-term ozone (O3) exposures by children living in urban communities, the authors analyzed longitudinal data on personal, indoor, and outdoor O3 concentrations, as well as related housing and other questionnaire information collected in the one-year-long Harvard Southern California Chronic Ozone Exposure Study. Of 224 children contained in the original data set, 160 children were found to have longitudinal measurements of O3 concentrations in at least six months of 12 months of the study period. Data for these children were randomly split into two equal sets: one for model development and the other for model validation. Mixed models with various variance-covariance structures were developed to evaluate statistically important predictors for chronic personal ozone exposures. Model predictions were then validated against the field measurements using an empirical best-linear unbiased prediction technique. The results of model fitting showed that the most important predictors for personal ozone exposure include indoor O3 concentration, central ambient O3 concentration, outdoor O3 concentration, season, gender, outdoor time, house fan usage, and the presence of a gas range in the house. Hierarchical models of personal O3 concentrations indicate the following levels of explanatory power for each of the predictive models: indoor and outdoor O3 concentrations plus questionnaire variables, central and indoor O3 concentrations plus questionnaire variables, indoor O3 concentrations plus questionnaire variables, central O3 concentrations plus questionnaire variables, and questionnaire data alone on time activity and housing characteristics. These results provide important information on key predictors of chronic human exposures to ambient O3 for children and offer insights into how to reliably and cost-effectively predict personal O3 exposures in the future. Furthermore, the techniques and findings derived from this study also have strong implications for selecting the most reliable and cost-effective exposure study design and modeling approaches for other ambient pollutants, such as fine particulate matter and selected urban air toxics.     

Impact of microenvironmental nitrogen dioxide concentrations on personal exposures in Australia

Indoor and outdoor NO2 concentrations were measured and compared with simultaneously measured personal exposures of 57 office workers in Brisbane, Australia. House characteristics and activity patterns were used to determine the impacts of these factors on personal exposure. Indoor NO2 levels and the presence of a gas range in the home were significantly associated with personal exposure. The time-weighted average of personal exposure was estimated using NO2 measurements in indoor home, indoor workplace, and outdoor home levels. The estimated personal exposures were closely correlated, but they significantly underestimated the measured personal exposures. Multiple regression analysis using other nonmeasured microenvironments indicated the importance of transportation in personal exposure models. The contribution of transportation to the error of prediction of personal exposure was confirmed in the regression analysis using the multinational study database.     

Impact of Microenvironmental Nitrogen Dioxide Concentrations on Personal Exposures in Australia

ABSTRACT

Indoor and outdoor NO₂ concentrations were measured and compared with simultaneously measured personal exposures of 57 office workers in Brisbane, Australia. House characteristics and activity patterns were used to determine the impacts of these factors on personal exposure. Indoor NO₂ levels and the presence of a gas range in the home were significantly associated with personal exposure. The time-weighted average of personal exposure was estimated using NO₂ measurements in indoor home, indoor workplace, and outdoor home levels. The estimated personal exposures were closely correlated, but they significantly underestimated the measured personal exposures. Multiple regression analysis using other nonmeasured microenvironments indicated the importance of transportation in personal exposure models. The contribution of transportation to the error of prediction of personal exposure was confirmed in the regression analysis using the multinational study database.     

Tetrachloroethylene Emissions and Exposure in Dry Cleaning

ABSTRACT

Tetrachloroethylene (PCE) emissions and the exposure of workers in six commercial and three industrial dry-cleaning establishments that use dry-to-dry machines were determined. The personal samples and area samples [8-hr time-weighted average (TWA) and short-term exposure] were collected with charcoal tubes and passive monitors. The temporal variation of PCE concentration in the workplace air was monitored using a Fourier transform infrared analyzer (FTIR). The PCE emission rates were determined by multiplying the average PCE concentration in the room and the total airflow rate in the room. The PCE emissions were related to the cleaning rate in units of kg/hr.

The operators' mean TWA exposure in commercial shops and industrial establishments was 28 (4.1 ppm) and 32 mg/m³ (4.6 ppm), and the pressers' exposure was 3.4 (0.5 ppm) and 7.7 mg/m³ (1.1 ppm), respectively. The customer service personnel had the lowest TWA exposure with a mean value of 0.8 mg/m³ (0.1 ppm). The highest peak concentration (2300 mg/m³; 334 ppm) was observed during cleaning of the lint and button trap, during which operation respirators were used. The PCE emission rates ranged from 4 to 118 g/hr corresponding to emission factors (mass of solvent evaporated per mass of cleaned cloths) of 0.3–3.6 g/kg. The workers' exposure to PCE was below the occupational limit values in the United States [according to the American Conference of Governmental Industrial Hygienists (ACGIH)] and in Finland. The outdoor PCE emissions were clearly below the limit values given in the European Union volatile organic compound (VOC) directive requirements.     

Filtration of Radioactive Aerosols By Glass Fibers

Abstract

An ozone (O₃) exposure assessment study was conducted in Toronto, Ontario, Canada during the winter and summer of 1992. A new passive O₃ sampler developed by Harvard was used to measure indoor, outdoor, and personal O₃ concentrations. Measurements were taken weekly and daily during the winter and summer, respectively. Indoor samples were collected at a total of 50 homes and workplaces of study participants. Outdoor O₃ concentrations were measured both at home sites using the passive sampler and at 20 ambient monitoring sites with continuous monitors. Personal O₃ measurements were collected from 123 participants, who also completed detailed time-activity diaries. A total of 2,274 O₃ samples were collected. In addition, weekly air exchange rates of homes were measured.

This study demonstrates the performance of our O₃ sampler for exposure assessment. The data obtained are further used to examine the relationships between personal, indoor (home and workplace), and outdoor O₃ concentrations, and to investigate outdoor and indoor spatial variations in O₃ concentrations. Based on home outdoor and indoor, workplace, and ambient O₃ concentrations measured at the Ontario Ministry of the Environment (MOE) sites, the traditional microenvironmental model predicts 72% of the variability in measured personal exposures. An alternative personal O₃ exposure model based on outdoor measurements and time-activity information is able to predict the mean personal exposures in a large population, with the highest R² value of 0.41.     

Formaldehyde personal exposure measurements and time weighted exposure estimates in children

Residential concentrations of formaldehyde have been associated with poor respiratory health in children, where formaldehyde has been measured using stationary monitors inside homes. Although children spend most of their time indoors at home, there are few studies of children’s personal exposure to formaldehyde. The aim of this study was to investigate the relationship between personal exposure formaldehyde concentrations, microenvironmental concentrations and time weighted exposure estimates in children.Forty-one primary school children (aged between 9 and 12 years) wore a personal passive sampler over two 24 h periods in two seasons and completed 24 h daily activity diaries and a questionnaire about lifestyle and behaviour. Samplers were co located indoors at home, outdoors at centralised locations and indoors at school for the corresponding period.Personal exposure formaldehyde concentrations in this group of children were generally low with a geometric mean concentration of 9.1 ppb (range <detection limit to 27.3 ppb). There were strong correlations between personal exposure concentrations and both domestic indoor (r_s = .779, p < 0.001) and time weighted estimated (r_s = .802, p < 0.001) concentrations. The time weighted model did not improve the estimate of personal exposure compared with stationary indoor concentrations. Indoor air concentration measured with a single stationary monitor was a suitable surrogate for personal exposure.     

Evaluation and investigation of the effects of ventilation layout,rate, and room temperature on pollution dispersion across a laboratory indoor environment

The presence of chemicals in laboratories and research centers exposes the staff working at such indoor environment to health risks. In this piece of research, a study was performed on the indoor environment of the Center for Environmental Engineering Research at Sahand University of Technology (Tabriz, Iran). For this purpose, the parameters affecting the dispersion of volatile organic compounds (VOCs), including ventilation rate, room temperature, pollution emission time, venting location, air flow regime within the indoor environment, and the number of vents, were simulated via CFD modeling. The CFD modeling was performed three-dimensionally in unsteady state. In case of turbulent flow within the indoor environment, k–ε turbulence model was used to obtain air velocity profile. Experimental data was used to validate the model. Results of the present research showed that when the venting location is on the ceiling, pollution concentration of 25 ppm can be achieved at some low temperature under a particular set of conditions. However, when the venting location was on the walls close to the pollution source, concentrations as low as 5 ppm and lower were observed within the laboratory indoor environment.

     

Evaluation of a Probabilistic Exposure Model Applied

The probabilistic National Ambient Air Quality Standards (NAAQS) Exposure Model applied to carbon monoxide (pNEM/CO) was developed by the U.S. Environmental Protection Agency (EPA) to estimate frequency distributions of population exposure to carbon monoxide (CO) and the resulting carboxyhemoglobin (COHb) levels. To evaluate pNEM/CO, the model was set up to simulate CO exposure data collected during a Denver Personal Exposure Monitoring Study (PEM) conducted during the winter of 1982-1983.

This paper compares computer-simulated exposure distributions obtained by pNEM/CO with the observed cumulative

relative frequency distributions of population exposure to CO from 779 people in the Denver PEM study. The subjects were disaggregated into two categories depending upon whether they lived in a home with a gas stove or an electric stove. The observed and predicted population exposure frequency distributions were compared in terms of 1-hr daily maximum exposure (1DME) and 8-hr daily maximum moving average exposure (8DME) for people living in homes with gas stove or an electric stove. For 1DME, the computer-simulated results from pNEM/CO agreed most closely within the range of 6-13 ppm, but overestimated occurrences at low exposure (<6 ppm) and underestimated occurrences at high exposure (>13 ppm). For 8DME, the predicted exposures agreed best with observed exposures in the range of CO concentration between 5.5 and 7 ppm, and over-predicted occurrences below 5.5 ppm and under-predicted occurrences above 7 ppm.