Household and personal air pollution exposure measurements from 120 communities in eight countries: results from the PURE-AIR study

BACKGROUND

Approximately 2·8 billion people are exposed to household air pollution from cooking with polluting fuels. Few monitoring studies have systematically measured health-damaging air pollutant (ie, fine particulate matter [PM2·5] and black carbon) concentrations from a wide range of cooking fuels across diverse populations. This multinational study aimed to assess the magnitude of kitchen concentrations and personal exposures to PM2·5 and black carbon in rural communities with a wide range of cooking environments.

METHODS

As part of the Prospective Urban and Rural Epidemiological (PURE) cohort, the PURE-AIR study was done in 120 rural communities in eight countries (Bangladesh, Chile, China, Colombia, India, Pakistan, Tanzania, and Zimbabwe). Data were collected from 2541 households and from 998 individuals (442 men and 556 women). Gravimetric (or filter-based) 48 h kitchen and personal PM2·5 measurements were collected. Light absorbance (10-5m-1) of the PM2·5 filters, a proxy for black carbon concentrations, was calculated via an image-based reflectance method. Surveys of household characteristics and cooking patterns were collected before and after the 48 h monitoring period.

FINDINGS

Monitoring of household air pollution for the PURE-AIR study was done from June, 2017, to September, 2019. A mean PM2·5 kitchen concentration gradient emerged across primary cooking fuels: gas (45 μg/m3 [95% CI 43-48]), electricity (53 μg/m3 [47-60]), coal (68 μg/m3 [61-77]), charcoal (92 μg/m3 [58-146]), agricultural or crop waste (106 μg/m3 [91-125]), wood (109 μg/m3 [102-118]), animal dung (224 μg/m3 [197-254]), and shrubs or grass (276 μg/m3 [223-342]). Among households cooking primarily with wood, average PM2·5 concentrations varied ten-fold (range: 40-380 μg/m3). Fuel stacking was prevalent (981 [39%] of 2541 households); using wood as a primary cooking fuel with clean secondary cooking fuels (eg, gas) was associated with 50% lower PM2·5 and black carbon concentrations than using only wood as a primary cooking fuel. Similar average PM2·5 personal exposures between women (67 μg/m3 [95% CI 62-72]) and men (62 [58-67]) were observed. Nearly equivalent average personal exposure to kitchen exposure ratios were observed for PM2·5 (0·79 [95% 0·71-0·88] for men and 0·82 [0·74-0·91] for women) and black carbon (0·64 [0·45-0·92] for men and 0·68 [0·46-1·02] for women).

INTERPRETATION

Using clean primary fuels substantially lowers kitchen PM2·5 concentrations. Importantly, average kitchen and personal PM2·5 measurements for all primary fuel types exceeded WHO's Interim Target-1 (35 μg/m3 annual average), highlighting the need for comprehensive pollution mitigation strategies.

FUNDING

Canadian Institutes for Health Research, National Institutes of Health.

Nanotoxicology: The Need for a Human Touch?

With the ever-expanding number of manufactured nanomaterials (MNMs) under development there is a vital need for nanotoxicology studies that test the potential for MNMs to cause harm to health. An extensive body of work in cell cultures and animal models is vital to understanding the physicochemical characteristics of MNMs and the biological mechanisms that underlie any detrimental actions to cells and organs. In human subjects, exposure monitoring is combined with measurement of selected health parameters in small panel studies, especially in occupational settings. However, the availability of further in vivo human data would greatly assist the risk assessment of MNMs. Here, the potential for controlled inhalation exposures of MNMs in human subjects is discussed. Controlled exposures to carbon, gold, aluminum, and zinc nanoparticles in humans have already set a precedence to demonstrate the feasibility of this approach. These studies have provided considerable insight into the potential (or not) of nanoparticles to induce inflammation, alter lung function, affect the vasculature, reach the systemic circulation, and accumulate in other organs. The need for further controlled exposures of MNMs in human volunteers - to establish no-effect limits, biological mechanisms, and provide vital data for the risk assessment of MNMs - is advocated.

A Procedure to Standardize Puff Topography During Evaluations of Acute Tobacco or Electronic Cigarette Exposure

INTRODUCTION

Documenting factors that influence differential sensitivity to acutely inhaled nicotine products requires carefully controlling the amount of exposure (dose), and thus a procedure by which to control such exposure.

METHODS

We evaluated consistency of puff volume from intermittent acute exposures to smoked tobacco cigarettes (study 1, n = 45, plus a comparison study of uninstructed use with n = 59) and to vaped electronic cigarettes (e-cigarettes; study 2, n = 27 naive to e-cigarettes) in adult-dependent smokers. All in primary studies 1 and 2 participated in research administering different nicotine levels in each product under blind conditions, one per session using within-subject designs. In both studies, participants followed an automated instructional procedure on a computer monitor standardizing the timing and amount of exposure to each product during a given trial, with four trials per session, each separated by 20 minutes. Puff volume per trial via Clinical Research Support System (CReSS) was the primary dependent measure to determine consistency across trials via intraclass correlation coefficients (ICCs).

RESULTS

Control over topography with both inhaled products was demonstrated by highly significant ICCs for puff volume across trials. Instructed control with own brand was generally better in study 1 than with uninstructed smoking in the comparison sample, as expected. As intended, reliability of puff volume generally did not differ by menthol preference or sex in either study, but ICCs in study 2 tended to be lower for some men using the placebo e-cigarette.

CONCLUSIONS

This instructional procedure may substantially improve control over amounts of acute exposure to tobacco or e-cigarette use.

IMPLICATIONS

Control over topography in studies of acute exposure to these inhaled products can potentially aid validity of research into differential sensitivity to use, so findings can be attributed to factors of interest and not to variable exposure. Our procedure minimized variability in exposure to the same product and between moderate nicotine products, but remaining differences suggest that compensation for very low or no nicotine commercial products may be difficult to totally eliminate with these instructions alone. Further study is needed to determine this procedure's utility with other inhaled products among experienced users and when comparing different products in between-groups analyses.

Trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E) (2018)

Trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-133mzz-E) is an odorless gas that finds uses as a foam transfer agent, heat transfer fluid, and specialty gas. The acute 4-h LC₅₀ (in rats) for HFO-133mzz-E is > 17,000 ppm; it was not an eye or dermal irritant in 3- and 13-week repeated-dose inhalation studies in rats at concentrations up to 1.5% (15,000 ppm). HFO-133mzz-E was not a cardiac sensitizer at 70,000 ppm in a standard epinephrine challenge study in Beagle dogs. In a 3-week, repeated-dose (non-GLP) inhalation range-finding study in male and female rats, HFO-133mzz-E concentrations of 7500 and 15,000 ppm were determined to be well-tolerated. In the follow-up, GLP-compliant, 28-day repeated-dose inhalation study (as per OECD 412), male and female rats were exposed to 0, 1000, 10,000, or 15,000/20,000 ppm (20,000 ppm concentration was decreased to 15,000 ppm after week 1 because of deaths and body weight loss). The study no-observed-adverse-effect level (NOAEL) was established at 10,000 ppm based on reduced body weight gain and mortality observed at 15,000 ppm. In a 90-day GLP-compliant repeated-dose study (as per OECD 413), male and female rats were exposed to 0, 1000, 5000, 7500, or 15,000 ppm HFO-133mzz-E. Three male rats exposed to 15,000 ppm HFO-133mzz-E died during exposure; clinical signs such as restlessness, blepharospasm, and myoclonic jerks were also observed, during the first month of the study, at 15,000 ppm. There were no significant gross or histopathological organ/tissue lesions attributable to HFO-133mzz-E exposure. The study NOAEL was established at 7500 ppm. In a GLP prenatal developmental study (OECD 414), groups of time-mated nulliparous female rats were exposed via inhalation to 0, 1000, 5000, 7500, or 15,000 ppm HFO-1336mzz-E beginning on gestation day (GD) 6 up to and including GD 19. Under the conditions of this study, the NOAEL for maternal and fetal effects was established at 7500 ppm. HFO-1336mzz-E was not genotoxic in either in vitro or in vivo assays. Based on the results of the 90-day inhalation study, 7500 ppm was determined to be the NOAEL and was selected as the point of departure for the derivation of the 8-h time-weighted average (TWA), health-based workplace environmental exposure level (WEEL) value. This subchronic inhalation NOAEL was adjusted to account for duration of exposure, interindividual variability, and intraindividual variability. The resulting 8-h TWA WEEL value of 400 ppm is fully expected to provide a significant margin of safety against the production of any potential adverse health effects in workers following long-term inhalation exposure to HFO-1336mzz-E.

Heavy metals (Cr, Pb, Cd, Ni) in aerosols emitted from electronic cigarettes sold in Malaysia

While past studies have detected heavy metals in aerosols emitted from electronic cigarettes (ECIG), they have provided little information detailing the practical implications of the findings to the Malaysian population due to variations between products. The aims of this study were to analyse heavy metals of interest (HMOI) in the aerosols emitted from selected ECIG and to evaluate potential health risks by referring to the permissible daily exposure (PDE) from inhalational medications defined by the United States Pharmacopeia Chapter 232. All four HMOI were detected in aerosols emitted from the selected ECIG in Sarawak. Among the four, Cr was present at the highest median levels (6.86 ng/m³), followed by Ni (0.30 ng/m³), Pb (0.19 ng/m³) and Cd (0.01 ng/m³). Five out of 100 combinations (5%) of ECIG and ECIG liquids were found to emit Cr that exceed the recommended PDE. Future studies examining more heavy metal variants, using a larger sample size and different analytical techniques to compare various ECIGs are recommended.

The quantitative assessment of the public excess disease burden advanced by inhalable particulate matter under different air quality standard targets in Tianjin, China

Currently, the quantitative assessment of the public excess risk for the update of the air quality guidelines only considered the mortality and morbidity without disease burden indicators. To provide evidences for the update of air quality guidelines and the policy analysis of air control, a simple framework to identify the excess disease burden of PM₁₀ was used in this study. Daily data on PM₁₀, meteorological factors, and deaths were collected in this 10-year (2001-2010) time series study in Tianjin, China. The excess disease burden advanced by PM₁₀ was assessed when the PM₁₀ levels exceeded the expected levels. Generalized additive model was used to estimate the associations of PM₁₀ with mortality and years of life lost (YLL). Our study found that the exposure of PM₁₀ was associated with the increasing of mortality and YLL in different diseases. The excess deaths and YLL of different diseases advanced by PM₁₀ when the PM₁₀ levels exceeded the expected levels were high and showed a decreasing trend from 2001 to 2010. The annual deaths and YLL standardized per million population advanced by PM₁₀ when the annual PM₁₀ levels exceeded the China national ambient air quality secondary standard targets (70 μg/m³) and WHO guideline (20 μg/m³) were 126 persons, 2670 person years and 260 persons, 5449 person years, respectively. This study may provide a simple framework to identify the excess disease burden of PM and provide basic and intuitive evidences to update the air quality guidelines. Furthermore, these findings may also provide decisionmakers with intuitive quantitative information for policymaking and emphasize health considerations in air quality policy discussions.

Sources and Characteristics of Polycyclic Aromatic Hydrocarbons in Ambient Total Suspended Particles in Ulaanbaatar City, Mongolia

The purpose of this study was to identify pollution sources by characterizing polycyclic aromatic hydrocarbons from total suspended particles in Ulaanbaatar City. Fifteen polycyclic aromatic hydrocarbons were measured in total suspended particle samples collected from different sites, such as the urban center, industrial district and ger (Mongolian traditional house) areas, and residential areas both in heating (January, March), and non-heating (September) periods in 2017. Polycyclic aromatic hydrocarbon concentration ranged between 131 and 773 ng·m-3 in winter, 22.2 and 530.6 ng·m-3 in spring, and between 1.4 and 54.6 ng·m-3 in autumn. Concentrations of specific polycyclic aromatic hydrocarbons such as phenanthrene were higher in the ger area in winter and spring seasons, and the pyrene concentration was dominant in late summer in the residential area. Polycyclic aromatic hydrocarbons concentrations in the ger area were particularly higher than the other sites, especially in winter. Polycyclic aromatic hydrocarbon ratios indicated that vehicle emissions were likely the main source at the city center in the winter time. Mixed contributions from biomass, coal, and petroleum combustion were responsible for the particulate polycyclic aromatic hydrocarbon pollution at other sampling sites during the whole observation period. The lifetime inhalation cancer risk values in the ger area due to winter pollution were estimated to be 1.2 × 10-5 and 2.1 × 10-5 for child and adult exposures, respectively, which significantly exceed Environmental Protection Agency guidelines.

Health risk of swimming pool disinfection by-products: a regulatory perspective

While disinfection of swimming pools is indispensable for microbiological safety, it may lead to the formation of disinfection by-products. Most studies agree that inhalation exposure is the predominant pathway of the associated health risks, but assumptions are based on concentrations measured in water and evaporation models. Pool water and air were sampled in 19 swimming pools. Trihalomethanes were detected in all sites; chloroform being the most abundant species. Concentrations ranged between 12.8-71.2 μg/L and 11.1-102.2 μg/m³ in pool water and air, respectively. The individual lifetime carcinogenic risk associated with chloroform in swimming pools exceeded 10^-6 in all age groups for recreational swimmers and 10^-5 for elite swimmers and staff, even if the pool complied with the national standards. Inhalation exposure was estimated and found to be the most relevant, however, different mass transfer models from water measurements significantly under- or overestimated the health burden compared to direct calculation from the concentration in air. The observed health risks call for defining regulatory values and monitoring requirement of indoor air quality in swimming pools.

Concentration-time extrapolation of short-term inhalation exposure levels: dimethyl sulfide, a case study using a chemical-specific toxic load exponent

OBJECTIVE

Dimethyl sulfide (DMS, CAS 75-18-3) is an industrial chemical. It is both an irritant and neurotoxicant that may be life-threatening because of accidental release. The effects of DMS on public health and associated public health response depend on the exposure concentration and duration. However, currently, public health advisory information exists for only a 1 h exposure duration, developed by the American Industrial Hygiene Association (AIHA). In the present work, the AIHA-reviewed data were computationally extrapolated to other common short-term durations.

METHODS

The extrapolation was carried out using the toxic load equation, Cn × t = TL, where C and t are exposure concentration and duration, TL is toxic load, and n is a chemical-specific toxic load exponent derived in the present work using probit meta-analysis. The developed threshold levels were vetted against the AIHA database of clinical and animal health effects induced by DMS.

RESULTS

Tier-1 levels were derived based on human exposures that resulted in an easily detectable odor, because DMS is known to have a disagreeable odor that may cause nausea. Tier-2 levels were derived from the lower 95% confidence bounds on a benchmark concentration that caused 10% incidence (BMCL10) of coma in rats during a 15 min inhalation exposure to DMS. Tier-3 levels were based on a BMCL05 for mortality in rats.

CONCLUSION

Emergency responders and health assessors may consider these computationally derived threshold levels as a supplement to traditional chemical risk assessment procedures in instances where AIHA developed public health advisory levels do not exist.

Polybrominated diphenyl ethers (PBDEs) in car and house dust from Thailand: Implication for human exposure

This study examines concentrations of tri- to hexa-bromodiphenylethers (BDEs 17, 28, 47, 49, 66, 85, 99, 100, 153 and 154; Σ₁₀PBDEs (polybrominated diphenyl ethers)) in car (n = 30) and house dust samples (n = 53) collected from different provinces in Thailand. The specific objectives of this study were: (i) to monitor levels of tri- to hexa-bromodiphenylethers (BDEs 17, 28, 47, 49, 66, 85, 99, 100, 153 and 154; Σ₁₀PBDEs) in vehicle and residential dust sampled from various provinces in Thailand; (ii) to compare PBDE concentrations with those detected for domestic and automobile dust in studies from other countries and (iii) to estimate exposure of the Thai population to the target PBDEs via dust ingestion. Levels of Σ₁₀PBDEs in vehicle and domestic dust were 0.68-38 and 0.59-260 ng g^-1, respectively. BDEs 99 and 47 were the most abundant congeners in all automobile and residential dust samples. A t-test analysis indicated that Σ₁₀PBDE concentrations in dust samples from dwellings exceeded significantly those from cars (p = 0.001). Furthermore, contents in dust of all PBDEs studied, except for BDE-28, were significantly higher in homes than in vehicles (p = 0.000-0.004). Principal Component Analysis (PCA) demonstrated no differences in PBDE congener patterns between Thai house and automobile dust, but revealed some subtle differences in the congener pattern between household dust samples in Thailand and those reported previously for the United Kingdom. Estimated environmental exposure of Thai adults and children for BDE-99 via dust ingestion were well within a chronic oral reference dose (RfD) for BDE-99 (100 ng/kg bw/day) proposed by the United States Environmental Protection Agency (US EPA).

Water-Based Automobile Paints Potentially Reduce the Exposure of Refinish Painters to Toxic Metals

Exposure to lead-containing dusts is a global public health concern. This work addresses an important issue of whether eco-friendly water-based paints reduce the exposure potential of auto-repainting workers to metals. With this aim, metal levels in automobile paints and worker metal exposure were measured using both solvent- and water-based paints. The levels of metals, and particularly Pb, Cr (total), Fe, and Cu, in solvent-based paints varied greatly among colors and brands. Lead concentrations ranged from below the detection limit (~0.25 μg/g) to 107,928 μg/g (dry film) across all samples. In water-based paints, the concentrations of Pb and Cr (total) were generally two to three orders of magnitude lower, but the concentrations of Al and Cu exceeded those in some solvent-based paints. The personal short-term exposure of workers who applied water-based paints of popular colors, such as black and white, were generally low, with Pb levels of less than <4 µg/m³ and Cr (total) levels of less than 1 µg/m³. Conversely, mean short-term exposure to Pb during the painting of a yellow cab using solvent-based paints were 2028 µg/m³, which was ~14 times the Taiwan short-term permissible exposure limit, while the mean level of exposure to Cr (total) was 290 µg/m³, which was well below the exposure limit. This study demonstrates that water-based paints reduce the exposure potential to lead, and highlights the importance of source control in limiting the toxic metals in paints.

Re-evaluation of the WHO (2010) formaldehyde indoor air quality guideline for cancer risk assessment

In 2010, the World Health Organization (WHO) established an indoor air quality guideline for short- and long-term exposures to formaldehyde (FA) of 0.1 mg/m3 (0.08 ppm) for all 30-min periods at lifelong exposure. This guideline was supported by studies from 2010 to 2013. Since 2013, new key studies have been published and key cancer cohorts have been updated, which we have evaluated and compared with the WHO guideline. FA is genotoxic, causing DNA adduct formation, and has a clastogenic effect; exposure-response relationships were nonlinear. Relevant genetic polymorphisms were not identified. Normal indoor air FA concentrations do not pass beyond the respiratory epithelium, and therefore FA's direct effects are limited to portal-of-entry effects. However, systemic effects have been observed in rats and mice, which may be due to secondary effects as airway inflammation and (sensory) irritation of eyes and the upper airways, which inter alia decreases respiratory ventilation. Both secondary effects are prevented at the guideline level. Nasopharyngeal cancer and leukaemia were observed inconsistently among studies; new updates of the US National Cancer Institute (NCI) cohort confirmed that the relative risk was not increased with mean FA exposures below 1 ppm and peak exposures below 4 ppm. Hodgkin's lymphoma, not observed in the other studies reviewed and not considered FA dependent, was increased in the NCI cohort at a mean concentration ≥0.6 mg/m3 and at peak exposures ≥2.5 mg/m3; both levels are above the WHO guideline. Overall, the credibility of the WHO guideline has not been challenged by new studies.

Setting Occupational Exposure Limits for Genotoxic Substances in the Pharmaceutical Industry

In the pharmaceutical industry, genotoxic drug substances are developed for life-threatening indications such as cancer. Healthy employees handle these substances during research, development, and manufacturing; therefore, safe handling of genotoxic substances is essential. When an adequate preclinical dataset is available, a risk-based decision related to exposure controls for manufacturing is made following a determination of safe health-based limits, such as an occupational exposure limit (OEL). OELs are calculated for substances based on a threshold dose-response once a threshold is identified. In this review, we present examples of genotoxic mechanisms where thresholds can be demonstrated and OELs can be calculated, including a holistic toxicity assessment. We also propose a novel approach for inhalation Threshold of Toxicological Concern (TTC) limit for genotoxic substances in cases where the database is not adequate to determine a threshold.

Estimation of the Human Extrathoracic Deposition Fraction of Inhaled Particles Using a Polyurethane Foam Collection Substrate in an IOM Sampler

Extrathoracic deposition of inhaled particles (i.e., in the head and throat) is an important exposure route for many hazardous materials. Current best practices for exposure assessment of aerosols in the workplace involve particle size selective sampling methods based on particle penetration into the human respiratory tract (i.e., inhalable or respirable sampling). However, the International Organization for Standardization (ISO) has recently adopted particle deposition sampling conventions (ISO 13138), including conventions for extrathoracic (ET) deposition into the anterior nasal passage (ET₁) and the posterior nasal and oral passages (ET₂). For this study, polyurethane foam was used as a collection substrate inside an inhalable aerosol sampler to provide an estimate of extrathoracic particle deposition. Aerosols of fused aluminum oxide (five sizes, 4.9 µm-44.3 µm) were used as a test dust in a low speed (0.2 m/s) wind tunnel. Samplers were placed on a rotating mannequin inside the wind tunnel to simulate orientation-averaged personal sampling. Collection efficiency data for the foam insert matched well to the extrathoracic deposition convention for the particle sizes tested. The concept of using a foam insert to match a particle deposition sampling convention was explored in this study and shows promise for future use as a sampling device.

Advances in Inhalation Dosimetry Models and Methods for Occupational Risk Assessment and Exposure Limit Derivation

The purpose of this article is to provide an overview and practical guide to occupational health professionals concerning the derivation and use of dose estimates in risk assessment for development of occupational exposure limits (OELs) for inhaled substances. Dosimetry is the study and practice of measuring or estimating the internal dose of a substance in individuals or a population. Dosimetry thus provides an essential link to understanding the relationship between an external exposure and a biological response. Use of dosimetry principles and tools can improve the accuracy of risk assessment, and reduce the uncertainty, by providing reliable estimates of the internal dose at the target tissue. This is accomplished through specific measurement data or predictive models, when available, or the use of basic dosimetry principles for broad classes of materials. Accurate dose estimation is essential not only for dose-response assessment, but also for interspecies extrapolation and for risk characterization at given exposures. Inhalation dosimetry is the focus of this paper since it is a major route of exposure in the workplace. Practical examples of dose estimation and OEL derivation are provided for inhaled gases and particulates.

Radon and thoron levels, their spatial and seasonal variations in adobe dwellings - a case study at the great Hungarian plain

Radon and thoron isotopes are responsible for approximately half of the average annual effective dose to humans. Although the half-life of thoron is short, it can potentially enter indoor air from adobe walls. Adobe was a traditional construction material in the Great Hungarian Plain. Its major raw materials are the alluvial sediments of the area. Here, seasonal radon and thoron activity concentrations were measured in 53 adobe dwellings in 7 settlements by pairs of etched track detectors. The results show that the annual average radon and thoron activity concentrations are elevated in these dwellings and that the proportions with values higher than 300 Bq m(-3) are 14-17 and 29-32% for radon and thoron, respectively. The calculated radon inhalation dose is significantly higher than the world average value, exceeding 10 mSv y(-1) in 7% of the dwellings of this study. Thoron also can be a significant contributor to the inhalation dose with about 30% in the total inhalation dose. The changes of weather conditions seem to be more relevant in the variation of measurement results than the differences in the local sedimentary geology. Still, the highest values were detected on clay. Through the year, radon follows the average temperature changes and is affected by the ventilation, whereas thoron rather seems to follow the amount of precipitation.

Perlite toxicology and epidemiology--a review

Perlite is a generic name for an amorphous volcanic alumina-silicate rock that expands by a factor of 4-20 when rapidly heated to 1400-1800 °F (760-980 °C). Both the ore and the expanded product have extensive and widespread commercial applications. Limited data on the toxicology of perlite in animal studies indicate that the LD₅₀ (oral ingestion) is more than 10 g/kg and, from a chronic inhalation study in guinea pigs and rats, that the NOAEL for the inhalation pathway is 226 mg/m³. Health surveillance studies of workers in US perlite mines and expansion plants (including some workers exposed to levels greater than prevailing occupational exposure limits (OELs) conducted over 20 years indicate that the respiratory health of workers is not adversely affected. Studies in Turkish mines and expanding plants had generally similar results, but are more difficult to interpret because of high smoking rates in these populations. A recent mortality study of permanent residents of the island of Milos (Greece) exposed to various mining dusts (including perlite) resulted in non-significant increases in standard mortality ratios for pneumonia and chronic obstructive pulmonary disease (COPD), whereas a companion morbidity study revealed elevated odds ratios for allergic rhinitis, pneumonia, and COPD when compared to another industrial area of Greece. Residents were exposed to other mining dusts and other possible causes or contributing factors and no ambient monitoring data were presented so it is not possible to use this study for risk calculations of perlite-exposed populations. Perlite is regulated as a "nuisance dust" in most countries.

[Indoor air guide values for 2-ethylhexanol]

The German Ad-hoc Working Group on Indoor Guidelines of the Indoor Air Hygiene Committee and of the Supreme State Health Authorities is issuing indoor air guide values to protect public health. 2-Ethylhexan-1-ol (EH) is used amongst others as an intermediate in the production of plasticisers or as a flavouring agent in food, cosmetics and cleaning agents. EH is detectable in nearly all indoor air samples. Indoor air concentrations in Germany were reported to be in the range of 0.002 to 0.006 mg/m3 (median), the 95-percentiles were in the range of 0.009 to 0.03 mg/m3. Toxicity after acute exposure to EH is low. EH is irritating to skin and eyes after direct contact. Acute exposure of humans to 54 mg EH/m3 caused sensory irritation (NOAEC 8 mg EH/m3). In a subchronic inhalation study in rats, neither local nor systemic effects were detectable up to the highest concentration tested (638 mg/m3). EH is not genotoxic and not carcinogenic in rats and male mice after oral application. There is no evidence that EH impairs fertility. Developmental toxicity was only observed at doses, which already caused maternal toxicity (650 mg/kg bw/d). Sensory irritation is the most relevant effect for the derivation of indoor air guide values. Based on a LOAEC of 54 mg/m3 and a NOAEC of 8 mg/m3 in a short time (4 h) inhalation study with volunteers, and applying an intraspecies extrapolation factor of 10 and a factor of 6 for time extrapolation, a preliminary hazard-based guide value of 1 mg EH/m3 and a preliminary precautionary value of 0.1 mg EH/m3 have been derived.

Asbestos Exposures during Reprocessing of Automobile Brakes and Clutches

Asbestos exposures of workers in three small factories reprocessing automobile brakes and clutches in Japan were investigated. Airborne asbestos was collected on a membrane filter using an air sampler. From 1982 to 1989, asbestos counting was performed on 295 samples (198 personal and 97 stationary), using phase contrast microscopy. Only chrysotile asbestos was detected. Workers who reprocessed automobile brakes and clutches were exposed to asbestos concentrations of 0.025-76.4 fibers/cm3. Geometric mean asbestos concentrations during attaching linings to brake shoes and attaching facings to clutch disks were 0.859 fibers/cm3 and 0.780 fibers/cm3, respectively. Concentrations during stripping worn brake linings and clutch facings were 0.484 fibers/cm3 and 0.382 fibers/cm3, respectively. Machine grinding and leveling of new brake-lining surfaces represent potential sources of heavy asbestos exposures, unless enclosures and local ventilation are efficient.

Development of worker inhalation derived no effect levels for tungsten compounds

Under the European Community (EC) Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), the risk to humans may be considered controlled if the estimated exposure levels to a substance do not exceed the appropriate derived no-effect level (DNEL). In order to address worker exposure, DNELs are derived for the worker population. The most significant route of exposure to workers to both soluble and sparingly soluble tungsten substances is through inhalation. In order to meet the REACH registration requirements, occupational long-term inhalation DNELs were developed according to the European Chemical Agency (ECHA) REACH guidance on characterization of dose-response for human health. The inhalation DNELlong-term for sodium tungstate, from which all other soluble tungsten substance DNELs were derived, is 3 mg sodium tungstate/m(3) (1.7 mg W/m(3)), and the inhalation DNELlong-term for tungsten blue oxide, from which all other sparingly soluble tungsten substance DNELs were derived, is 7.3 mg tungsten blue oxide/m(3) (5.8 mg tungsten/m(3)). Although derived using different methodologies and supported by different studies, the occupational inhalation DNELslong-term for soluble and sparingly soluble tungsten compounds are similar to the current National Institute for Occupational Safety and Health (NIOSH) recommended exposure level (REL) and the American Conference of Industrial Hygienists (ACGIH) threshold limit value (TLV) 8-h time weighted average (TWA) of 1 mg tungsten/m(3) for soluble tungsten compounds and 5 mg tungsten/m(3) as metal and insoluble tungsten compounds.

[Validation of measurement methods and estimation of uncertainty of measurement of chemical agents in the air at workstations]

This paper reviews the requirements for measurement methods of chemical agents in the air at workstations. European standards, which have a status of Polish standards, comprise some requirements and information on sampling strategy, measuring techniques, type of samplers, sampling pumps and methods of occupational exposure evaluation at a given technological process. Measurement methods, including air sampling and analytical procedure in a laboratory, should be appropriately validated before intended use. In the validation process, selected methods are tested and budget of uncertainty is set up. The validation procedure that should be implemented in the laboratory together with suitable statistical tools and major components of uncertainity to be taken into consideration, were presented in this paper. Methods of quality control, including sampling and laboratory analyses were discussed. Relative expanded uncertainty for each measurement expressed as a percentage, should not exceed the limit of values set depending on the type of occupational exposure (short-term or long-term) and the magnitude of exposure to chemical agents in the work environment.

Critical evaluation of approaches in setting indoor air quality guidelines and reference values

The importance of good indoor air quality for the health of the individual was recognized as long as 150 years ago and that period also saw recommendations, which essentially related to questions of ventilation and carbon dioxide. The first evaluation standards for organic and inorganic substances were laid down in the 1970s, often on an empirical basis. It was in the mid-1980s of the 20th century that a shift occurred towards systematically evaluating the results of indoor air measurements, carrying out representative environmental surveys and deriving guideline values and reference values on the basis of toxicological, epidemiological and statistical criteria. Generally speaking the indoor environment is an area which can only be assessed with difficulty since its occupants are in most cases exposed to mixtures of substances and there can be great local and temporal variations in the substance spectrum. Data are available today for a large number of substances and this makes it possible, with the aid of statistically derived reference values and toxicologically based guideline values, to make useful recommendations regarding good indoor air quality. Nevertheless, it is still difficult to evaluate reactive compounds and reaction products. What is disadvantageous, however, is the fact that different guideline values may be published for one and the same substance, whose justification and area of application are often not transparent. A guideline or reference value can only be regarded as rational when necessary and when a strategy for its verification is available.

Health impact assessment of a reduction in ambient PM(2.5) levels in Spain

BACKGROUND

Health effects linked to exposure to high air pollutant levels have been described in depth, and many recent epidemiologic studies have also consistently reported positive associations between exposure to air pollutants at low concentrations (particularly PM(2.5)) and adverse health outcomes.

OBJECTIVE

To estimate the number of avoidable deaths associated with reducing PM(2.5) levels in Spain.

MATERIALS AND METHODS

For exposure assessment, we used the US Environmental Protection Agency's Community Multiscale Air Quality model to simulate air pollution levels with a spatial resolution of 18×18 km(2). Two different scenarios were compared, namely, a baseline 2004 scenario based on Spain's National Emissions Inventory and a projected 2011 scenario in which a reduction in PM(2.5) was estimated on the basis of the benefits that might be attained if specific air quality policies were implemented. Using an 18×18 km(2) grid, air pollution data were estimated for the entire Iberian Peninsula, the Balearic Islands, Ceuta and Melilla. For these strata, crude all-cause mortality rates (ICD-10: A00-Y98) were then calculated for the over-30 and 25-74 age groups, taking into account the 2004 population figures corresponding to these same age groups, selected in accordance with the concentration-response functions (Pope CA 3rd, Burnett RT, Thun MJ, Calle EE, Krewski D, Ito K et al. Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA 2002; 287:1132-41; Laden F, Schwartz J, Speizer FE, Dockery DW. Reduction in fine particulate air pollution and mortality: extended follow-up of the Harvard Six Cities study. Am J Respir Crit Care Med 2006; 173:667-72.). Health impacts were assessed using the Environmental Benefits Mapping and Analysis Program (BenMAP).

RESULTS

Air quality improvement was defined as an average annual reduction of 0.7 μg/m(3) in PM(2.5) levels. Using long-term health impact assessment analysis, we estimated that 1720 (673-2760) all-cause deaths (6 per 100,000 population) in the over-30 age group and 1450 (780-2108) all-cause deaths (5 per 100,000 population) in the 25-74 age group could be prevented annually.

CONCLUSIONS

The results showed the potential benefits in general mortality which could be expected if pollution control policies were successfully implemented by 2011. A specifically adapted BenMAP could be used as a tool for estimating health impacts associated with changes in air pollution in Spain.

Proposal for a revised reference concentration (RfC) for mercury vapour in adults

Worldwide, approximately 30-50 millions of people are living in small scale gold mining areas and are primarily burdened by mercury vapour. In the frame of our study, 306 mercury (Hg) vapour burdened adults, working and/ or living in two small scale gold mining areas in Zimbabwe and Tanzania and 58 volunteers from near-by unburdened communities were medically investigated. In addition, blood, urine and hair samples from each participant were analyzed for mercury. Altogether, 26 anamnestic and 24 clinical signs and symptoms, which may be caused by Hg vapour, were evaluated. Multivariate analysis was performed to investigate the influence of the mercury concentration in the bio-monitors on the evaluated anamnestic and clinical signs and symptoms taking into account age, gender, health status, alcohol consumption, use of pesticides and gasoline sniffing. Out of the resulting correlations between concentration and effect, ROC-curves were calculated to determine best estimates of the cut-off-values in the bio monitors. For the parameters ataxia of gait and sadness cut-off-values of 4.7 and 3.6 microg Hg/g crea in urine were calculated. These values were converted to a rounded LOAEL of 3.5 microg Hg vapour/m(3) air. In analogy to the US EPA Report (U.S. Environmental Protection Agency 1997) and the European Position Paper (Pirrone et al. 2001), uncertainty factors of 30 and 50 were applied, resulting in a proposed reference concentration (RfC) in ambient air of 0.1 microg Hg vapour/m(3) and 0.07 microg Hg vapour/m(3), respectively.

BBQ charcoal combustion as an important source of trace metal exposure to humans

To provide information about charcoal combustion as an important source of atmospheric trace metal pollution, 11 charcoal products were combusted and PM(10) filter samples were collected. The PM-bound metal elements were extracted by microwave acid digestion and analyzed by ICP-AES. The concentrations of trace metal elements ranged from a few to 10(5)ng m(-3) in the following order of magnitude: Zn>Pb>Mg>Ba>Cu>V>Cr>Co>Cd>Ni>Mn>Se>As. Emissions of most elements from charcoal combustion were high compared to other sources. In case of Cd, Co, and Ni, their concentrations exceeded the inhalation minimum risk levels (MRLs) of the United States Agency for Toxic Substances and Disease Registry (US-ATSDR) for chronic duration exposure by a factor of 30, 3.9, and 2.2, respectively. Likewise, Cd levels exceeded the US-ATSDR MRLs for acute-duration exposure by a factor of 10, while those of Pb and Cd exceeded air quality guideline (AQG) of the World Health Organization (WHO) by a factor of 29 and 59, respectively. Mn levels also exceeded the United States Environmental Protection Agency (US EPA) Reference Air Concentrations (RfCs) by a factor of 2.7. This study shows that barbecue charcoal combustion can be an important source of trace metal emissions to the atmosphere with potential health risks.

Comparison of two in vitro models of cigarette smoke exposure

Cigarette smoke is associated with a high morbidity and mortality, and affects particularly the respiratory tract. Various in vitro models have been developed to study the effects of cigarette smoke on bronchial epithelial cells. To identify an adequate exposure model of cigarette smoke, we analysed the effects of cigarette smoke extract (CSE) and a smoking chamber on bronchial epithelial cells. The release of monocyte chemoattractant protein (MCP)-1, interleukin (IL)-10, and vascular endothelial growth factor (VEGF) was measured. Bronchial epithelial cells isolated from Sprague-Dawley rat (NRBE) were exposed to 3% CSE or air control every day for 3 days. In the second model, NRBE were placed in an air/liquid interface and exposed, in a smoking chamber, to whole smoke from 2 cigarettes, twice daily for 3 days. Levels of MCP-1, IL-10, and VEGF were measured by enzyme-linked immunosorbent assay (ELISA), 24 h after the last exposure. The pattern of MCP-1 production by bronchial epithelial cells was different between the two models. MCP-1 release was increased after 3 days of exposure in the CSE model, but was inhibited using the smoking chamber model. Production of IL-10 by NRBE was reduced after 3 days in both models. Finally, no difference was observed in the production of VEGF between the two models. CSE and the smoking chamber differently modulate bronchial epithelial cell mediator production, demonstrating that the model of cigarette smoke exposure used can influence the data obtained.

Equipment, exposure, emission review--specification of process equipment for worker exposure control

Worker exposure to chemical agents may occur from equipment leaks in closed processes and from open system activities and maintenance (e.g., sampling, tank gauging, line breaking, equipment flushing, and drainage). To prevent worker overexposure to chemical agents, an Equipment, Exposure, Emission Review (EEER) was developed to consistently match equipment properties to the leakage-related inhalation risk posed by each stream. For streams where gas or liquid leakage could cause worker exposure above occupational exposure limits (OEL), the EEER recommended a high performance, low leakage equipment category. Conversely, where standard engineering offered reliable containment for lower health risk streams, the EEER did not recommend over-control. The EEER matched equipment to stream health hazard as follows: (1) the composition of each stream was determined, with particular attention to chemical substances with stringent exposure limits; (2) a mixture exposure limit was calculated for each stream based on stream composition and the OEL for stream constituent chemicals; (3) each stream was classified as to its respiratory exposure hazard on the basis of the stream exposure limit; (4) equipment was recommended as a function of respiratory exposure hazard class using an Equipment Selection Matrix. Equipment options were based, in part, on the emission performance of the equipment and a near-field dispersion model that was used to relate equipment emissions to an OEL. Over a 5-yr implementation period, nearly 1700 streams of 78 refining process units were reviewed. Standard engineering practice was selected for about 70% of the streams reviewed. Benzene, hydrogen sulfide, ethanolamine, and high boiling aromatic oil streams were the primary chemical agents responsible for more stringent controls. Although the EEER criteria for stream classification and control options were arranged in order of magnitude--a form of control banding--the correct selection of control technology was based on detailed assessment of stream composition and risk, rather than on process unit name or function. The EEER and Equipment Selection Matrix provided reproducible recommendations and helped manage cost and complexity of equipment specification for health protection.

Beryllium surface levels in a military ammunition plant

This study evaluated the presence of beryllium surface contamination in a U.S. conventional munitions plant as an indicator of possible past beryllium airborne and skin exposure and used these measurements to classify job categories by potential level of exposure. Surface samples were collected from production and nonproduction areas of the plant and at regional industrial reference sites with no known history of beryllium use. Surface samples of premoistened wiping material were analyzed for beryllium mass content using inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and results expressed as micrograms of beryllium per 100 square centimeters (micro g/100 cm(2)). Beryllium was detected in 87% of samples collected at the munitions plant and in 72% of the samples collected at regional reference sites. Two munitions plant samples from areas near sanders and grinders were above 3.0 micro g/100 cm(2) (U.S. Department of Energy surface contamination limit). The highest surface level found at the reference sites was 0.44 micro g/100 cm(2). Workers in areas where beryllium-containing alloy tools were sanded or ground, but not other work areas, may have been exposed to airborne beryllium concentrations above levels encountered in other industries where metal work is conducted. Surface sampling provided information useful for categorizing munitions plant jobs by level of past beryllium airborne and skin exposure and, subsequently, for identifying employees within exposure strata to be screened for beryllium sensitization.

[Assessment of carcinogenicity of formaldehyde based on the newest literature data]

In 2004, the category of formaldehyde carcinogenicity was changed in Poland so that it is now coherent with the requirements of the European Union classification of carcinogenicity. Formaldehyde was categorized into group 3 as the substance not classifiable as to its carcinogenecity to humans because the collected information was not adequate for making a satisfactory assessment. There is some evidence from appropriate animal studies, but it is insufficient to categorize this substance in group 2: probably carcinogenic to humans. In 2006, the International Agency for Research on Cancer categorized formaldehyde in group 1 as the substance carcinogenic to humans. Three types of cancer were assessed: nasopharyngeal cancer, leukemia and sinonasal cancer. There was sufficient evidence that formaldehyde causes nasopharyngeal cancer, strong but not sufficient evidence that the substance induces leukemia and limited evidence for sinonasal cancer. Based on the irritation effect, the value of maximum admissible concentration of formaldehyde in the work environment has been established in Poland at 0.5 mg/m3 as average weighed concentration, and 1 mg/m3 as short-term concentration. In the European Union, the values of 0.2 ppm and 0.4 ppm, respectively are now being considered. It is assumed that the MAC value for formaldehyde in the work environment will be soon verified in Poland and adapted to European Union standards.

Airborne particulate matter and premature deaths in urban Europe: the new WHO guidelines and the challenge ahead as illustrated by Spain

Twenty first century epidemiological publications on urban air pollution are confirming that inhalation of fine, airborne particulate matter (PM) has serious chronic human health effects and is a major cause of premature death worldwide. Recently updated recommendations by WHO identify three "Interim Targets" for the stepped reduction in PM levels within world cities in the quest to achieve an annual mean Air Quality Guideline (AQG) concentration of 20 mug/m(3) for particles less than 10 microns in size (PM(10)). In this paper we offer a perspective from Spain, a country with the longest record of reporting pollution data from large numbers of urban traffic sites to a central European database (AIRBASE). We can demonstrate that average annual PM concentrations at urban traffic monitoring stations in many European cities continue to be 50-100% above the WHO AQG, a situation exacerbated by high urban PM(2.5/10) ratios which indicate a dominance of finer, more deeply inhalable particles potentially more detrimental to health. Given that WHO has estimated in 2000 there were well over 250,000 premature deaths in Europe attributable to PM inhalation, such continuing high urban pollution levels are placing a huge burden on European medical resources.

Risk assessment of exposure to indoor aerosols associated with Chinese cooking

Cooking is an important source of indoor aerosols in residential homes and buildings with non-smokers, and thus has public health implications. However, limited information is currently available in the published literature on the physical and chemical characteristics of aerosols produced by gas cooking. Consequently, a comprehensive study was carried out to investigate the physical (number and mass concentrations and size distributions) and chemical (metals) properties in a typical Chinese food stall in Singapore where stir-frying in a wok is the most common cooking method using gas stove. To assess the contribution of cooking activities to indoor particle concentrations, aerosol measurements were performed in two distinct time periods, i.e., during cooking and non-cooking hours. The average mass concentrations of fine particles (PM(2.5)) and metals increased by a factor of 12 and 11, respectively, from 26.7 and 1.5microgm(-3) during non-cooking hours to 312.4 and 15.6microgm(-3) during cooking hours. The average number concentration was also elevated by a factor of 85, from 9.1x10(3)cm(-3) during non-cooking hours to 7.7x10(5)cm(-3) during cooking hours. Real-time particle measurements showed that about 80% of the particles associated with cooking are ultrafine particles in terms of particle counts. To evaluate the potential health threat due to inhalation of air pollutants released from gas cooking, the health risk estimates based on exposure and dose-response assessments of metals were calculated for a maximally exposed individual. The findings indicate that the indoor air quality existing at the food stall may pose adverse health effects over long-term exposure to cooking emissions.

Metalworking fluid mist occupational exposure limits: a discussion of alternative methods

NIOSH published a recommended exposure limit (REL) for metalworking fluids (MWF) in 1998 that was designed to prevent respiratory disorders associated with these industrial lubricants. The REL of 0.4 mg/m(3) (as a time-weighted average for up to 10 hours) was for the fraction of aerosol corresponding to deposition in the thoracic region of the lungs. This nonregulatory occupational exposure limit (OEL) corresponded to approximately 0.5 mg/m(3) for total particulate mass. Although this REL was designed to prevent respiratory disorders from MWF exposures, NIOSH acknowledged that exposures below the REL may still result in occupational asthma and hypersensitivity pneumonitis--two of the most significant respiratory illnesses associated with MWF. In the 8 years since the publication of the NIOSH MWF REL, neither the Occupational Safety and Health Administration (OSHA) nor the American Conference of Governmental Industrial Hygienists (ACGIH) has recommended an exposure limit for water-soluble MWF specifically, other than their previous exposure limits for mineral oil. An informal effort to benchmark companies involved in the manufacture of automobiles and automotive parts in North America indicated that most companies are using the NIOSH MWF REL as a guide for the purchase of new equipment. Furthermore, most companies have adopted a goal to limit exposures to below 1.0 mg/m3. We failed to find any company that has strictly enforced an OEL of 1.0 mg/m(3) through the use of either administrative controls or personal protective equipment, when engineering controls failed to bring the exposures to below this limit. We also found that most companies have failed to implement specific medical surveillance programs for those employees exposed to MWF mist above 1.0 mg/m(3). Organization Resources Counselors (ORC) published in 1999 (on their website) a "best practices" manual for maintaining MWF systems and reducing the likelihood of MWF-related illnesses. The emphasis of this approach was on control techniques, and there was no assignment of a specific OEL for MWF due to the wide variety of fluids that exist. The ORC did suggest that maintaining exposure levels to below 2.0 mg/m(3) would assist in minimizing upper respiratory complaints associated with MWF. Although the ORC manual indicated that MWF vary in composition and no single OEL is likely to be appropriate for all such fluids, it adopted a very similar concept to control banding, placing all MWF operations into a single band using similar (if not identical) controls. OSHA, in lieu of adopting a 6B health standard for MWF, has also published a voluntary "best practices" manual on their website. Their document drew heavily from the work of ORC and also incorporated information from the 1998 NIOSH MWF criteria document. Industrial users of MWF need to have guidance, such as an OEL, to determine when either engineering, administrative controls, or personal protective equipment must be implemented to protect their employees. The purpose of this article is to explore various approaches that might be taken to result in a single or multiple limits for exposures to MWF and its components. Approaches such as control banding are discussed in terms of an alternative to the use of an OEL.

Application of Physiologically Based Pharmacokinetic Modeling in Setting Acute Exposure Guideline Levels for Methylene Chloride

Acute exposure guideline levels (AEGLs) are derived to protect the human population from adverse health effects in case of single exposure due to an accidental release of chemicals into the atmosphere. AEGLs are set at three different levels of increasing toxicity for exposure durations ranging from 10 min to 8 h. In the AEGL setting for methylene chloride, specific additional topics had to be addressed. This included a change of relevant toxicity endpoint within the 10-min to 8-h exposure time range from central nervous system depression caused by the parent compound to formation of carboxyhemoglobin (COHb) via biotransformation to carbon monoxide. Additionally, the biotransformation of methylene chloride includes both a saturable step as well as genetic polymorphism of the glutathione transferase involved. Physiologically based pharmacokinetic modeling was considered to be the appropriate tool to address all these topics in an adequate way. Two available PBPK models were combined and extended with additional algorithms for the estimation of the maximum COHb levels. The model was validated and verified with data obtained from volunteer studies. It was concluded that all the mentioned topics could be adequately accounted for by the PBPK model. The AEGL values as calculated with the model were substantiated by experimental data with volunteers and are concluded to be practically applicable.

Probabilistic risk characterization: An example with di(2-ethylhexyl) phthalate

While probabilistic methods gain attention in hazard characterization and are increasingly used in exposure assessment, full use of the available probabilistic information in risk characterization is still uncommon. Usually, after probabilistic hazard characterization and/or exposure assessment, percentiles from the obtained distributions are used as point estimates in risk characterization. In this way, all information on variability and uncertainty is lost, while these aspects are crucial in any risk assessment. In this paper, we present a method to integrate the entire distributions from probabilistic hazard characterization and exposure assessment into one risk characterization plot. This method is illustrated using di(2-ethylhexyl) phthalate as an example. The final result of this probabilistic risk assessment is summarized in a single plot, containing two pieces of information: the confidence we may have in concluding there is no risk, and the fraction of the population this conclusion applies to. This information leads to a better informed conclusion on the risk of a substance, and may be very useful to define the necessary measures for risk reduction.

Acute inhalative exposure assessment: Derivation of guideline levels with special regard to sensitive subpopulations and time scaling

Risk assessment for acute airborne exposure to volatile organic compounds (VOCs), including exposure to chemical warfare agents, requires consideration of local and systemic effects at high concentrations. The operating procedure developed by the US Acute Exposure Guideline Level (AEGL) committee has gained special attention, in part because of the international collaboration in the project. The procedure defines three levels (AEGL-1: discomfort; AEGL-2: irreversible or other serious, long-lasting adverse effects; AEGL-3: life-threatening effects or death) for different exposure times (10 and 30 min, and 1, 4 and 8 h). In this article, the methodology for deriving AEGL values is reported. Extending the areas covered by the existing AEGL methodology, sensitive subpopulations are dealt with in more detail. Sensitive persons are expected to suffer from stronger effects when exposed to a given external concentration. Using a kinetic model with the sample substance dichloromethane (DCM), the higher internal exposure of children is quantified and compared to a healthy, young adult. The difference is shown to depend on age, on dose, and on duration of exposure. Furthermore, several ways are presented to derive AEGL values for exposure times which differ from the exposure duration in animal studies ('time scaling'). In comparison to the conventional procedure, the alternative approaches are based on mechanistic models of the toxicodynamic effect. Use of these models results in AEGL values which are biologically justified.

Acute toxicity and cancer risk assessment values for tert-butyl acetate

tert-Butyl acetate (TBAc) is an industrial chemical with potential uses as a degreaser and in architectural coatings. Limited chronic toxicity data exist for TBAc. However, acute inhalation exposure data are available for TBAc. Additionally, TBAc has been demonstrated to be substantially metabolized to tert-butanol (TBA) in rats, and a positive TBA genotoxicity study suggests that TBA may cause oxidative DNA damage. TBA has been shown to induce tumors in both rats and mice, and the Office of Environmental Health Hazard Assessment has calculated an oral cancer potency factor (CSF) for TBA of 3 x 10(-3)(mg/kg-day)(-1). Therefore, TBAc should be considered to pose a potential cancer risk to humans because of the metabolic conversion to TBA. An acute 1-h reference exposure level of 1 mg/m3 can be calculated from the extrapolated no observed adverse effect level of 50 mg/m3. A CSF of 0.002(mg/kg-day)(-1) can be derived for TBAc, assuming 100% metabolism of TBAc to TBA. An inhalation unit risk value for TBAc of 4 x 10(-7)(microg/m(3))(-1) can then be derived from the CSF value for TBAc by assuming a human breathing rate of 20 m3/day, 70% fractional absorption, and an average human body weight of 70 kg.

Measuring progress in the management of ambient air quality: the case for population health

Although progress has been made in the last few decades at reducing ambient concentrations of air pollutants, scientific evidence suggests that there remains a risk to human health from exposure to these pollutants at current levels in Canada. Much of the motivation for air pollution reduction efforts is to protect population health. This article presents a method of monitoring changes in air pollution-related health outcomes over time in conjunction with temporal changes in ambient pollution concentrations. The progress measure is a function of temporal changes in location-specific ambient concentrations and the potentially time-dependent association between those concentrations and daily deaths. The progress measure can be determined for a single location or at a national level. The measure can also be extended to include several pollutants. The progress measure is illustrated with an example of how changes in nitrogen dioxide levels in 12 Canadian cities from 1981 to 1999 have translated into changes in the percent of nonaccidental mortality burden attributable to this pollutant over time.

Characterizing and controlling industrial dust: a case study in small particle measurement

Instrumentation used to measure characteristics of fine particles entrained in gas or suspended in aerosols provides information needed to develop valid regulations for emission sources and to support the design of control technologies. This case study offers a brief history of "micromeritics," a term used by early researchers to describe the science of small particles, and the related invention of laboratory instruments for characterizing very fine particles. The historical view provides insights into the role that Progressive Era government agencies played in advancing esoteric science and applying this knowledge to the regulation of workplace air pollution. Micromeritics instrumentation developed in conjunction with federal research now has many commercial applications worldwide, with characterizing airborne pollutants only a minor one. However, the continuing advances in the micromeritics field provide important laboratory measurement capabilities to environmental research organizations, such as the National Institute for Occupational Safety and Health (NIOSH).

Health-related aerosol measurement: a review of existing sampling criteria and proposals for new ones

Interest in particle size-selective sampling for aerosols in working and ambient living environments began in the early 1900s when it became apparent that the penetration into-and deposition in-the respiratory tract of aerosol-exposed humans of inhaled particles was dependent on particle size. Coarse particles tended to be filtered out during inhalation and in the upper parts of the respiratory tract, so only progressively smaller particles penetrated down to the deep regions of the lung. Over time, following experimental studies with 'breathing' mannequins in wind tunnels and with human volunteer subjects in the laboratory, a clear picture has emerged of the physical, physiological and anatomical factors that control the extent to which particles may or may not reach certain parts of the respiratory tract. Such understanding has increasingly been the subject of discussions about aerosol standards, in particular the criteria by which exposure might be defined in relation to given classes of aerosol-related health effect-and in to turn aerosol monitoring. The ultimate goal has been to develop a set of criteria by which exposure standards are scientifically relevant to the health effects in question. This paper reviews the scientific basis for such criteria. It discusses the criteria that have already been widely discussed and so are either being applied or are on the threshold of practical application in standards. It also discusses how new advanced knowledge may allow us to extend the list of particle size-selective criteria to fractions that have not yet been widely discussed but which may be of importance in the future.

Total versus inhalable sampler comparison study for the determination of asphalt fume exposures within the road paving industry

Exposure to asphalt fumes has a threshold limit value (TLV of 0.5 mg m(-3) (benzene extractable inhalable particulate) as recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). This reflects a recent change (2000) whereby two variables are different from the previous recommendation. First is a 10-fold reduction in quantity from 5 mg m(-3) to 0.5 mg m(-3). Secondly, the new TLV specifies the "inhalable" fraction as compared to what is presumed to be total particulate. To assess the impact of these changes, this study compares the differences between measurements of paving asphalt fume exposure in the field using an "inhalable" instrument versus the historically used 'total' sampler. Particle size is also examined to assist in the understanding of the aerodynamic collection differences as related to asphalt fumes and confounders. Results show that when exposures are limited to asphalt fumes, a 1:1 relationship exists between samplers, showing no statistically significant differences in benzene soluble matter (BSM). This means that for the asphalt fume ACGIH TLV, the 'total' 37-mm sampler is an equivalent method to the "inhalable" method, referred to as IOM (Institute of Occupational Medicine), and should be acceptable for use against the TLV. However, the study found that when confounders (dust or old asphalt millings) are present in the workplace, there can be significant differences between the two samplers' reported exposure. The ratio of IOM/Total was 1.37 for milling asphalt sites, 1.41 for asphalt paving over granular base, and 1.02 for asphalt over asphalt pavements.