Gas-phase organics in environmental tobacco smoke: 2. Exposure-relevant emission factors and indirect exposures from habitual smoking

Sorption of emitted gas-phase organic compounds onto material surfaces affects environmental tobacco smoke (ETS) composition and exposures indoors. We have introduced a new metric, the exposure relevant emission factor (EREF) that accounts for sorptive uptake and reemission to give the mass of individual ETS constituents available for exposure over a day in which smoking occurs. This paper describes month-long experiments to investigate sorption effects on EREFs and potential ETS exposures under habitual smoking conditions. Cigarettes were smoked in a 50-m³ furnished room over a 3-h period 6–7 days per week, with continuous ventilation at 0.3, 0.6, or 2.1 h⁻¹. Organic gas concentrations were measured every few days over 4-h “smoking”, 10-h “post-smoking” and 10-h “background” periods. Concentration patterns of volatile ETS components including 1,3-butadiene, benzene and acrolein were similar to those calculated for a theoretical non-sorbing tracer, indicating limited sorption. Concentrations of ETS tracers, e.g. 3-ethenylpyridine (3-EP) and nicotine, and lower volatility toxic air contaminants including phenol, cresols, and naphthalene increased as experiments progressed, indicating mass accumulation on surfaces and higher desorption rates. Daily patterns stabilized after week 2, yielding a steady daily cycle of ETS concentrations associated with habitual smoking. EREFs for sorbing compounds were higher under steady cycle versus single-day smoking conditions by 50% for 3-EP, and by 2–3 times for nicotine, phenol, cresols, naphthalene, and methylnaphthalenes. Our results provide relevant information about potential indirect exposures from residual ETS (non-smoker enters room shortly after smoker finishes) and from reemission, and their importance relative to direct exposures (non-smoker present during smoking). Under the conditions examined, indirect exposures accounted for a larger fraction of total potential exposures for sorbing versus non-sorbing compounds, and at lower versus higher ventilation rates. Increasing ventilation can reduce indirect exposures to very low levels for non-sorbing ETS components, but indirect routes accounted for 50% of potential nicotine exposures during non-smoking periods at all ventilation rates.     

Exposure to benzene,toluene, xylenes and total hydrocarbons among snowmobile drivers in Sweden

The exposure to benzene, toluene, xylenes and total hydrocarbons among 25 individuals exposed to exhaust from a snowmobile equipped with a two-stroke engine has been evaluated. Sampling was performed by pumped and diffusive sampling in parallel. There was a relatively bad agreement between the two air-sampling methods. The bad agreement can in part be explained by back diffusion of the substances from the samplers, a high face velocity, and deposition of droplets of unburned gasoline onto or in the vicinity of the samplers.

The levels of benzene ranged from not detectable (0.01 mg m⁻³) to 2.5 mg m⁻³. For toluene, xylenes and total hydrocarbons the exposure was 0.10–12.0, 0.05–13.0 and 0.90–273 mg m⁻³ respectively. The result from two measurements on individuals travelling on an open sleigh at the rear of the vehicle indicated higher levels of benzene, 0.7–0.8 mg m⁻³. Children are often riding as a passenger on a sledge and may thus have a higher exposure than their parents. This study indicates that spare time driving a snowmobile may cause a considerable exposure to benzene. Using a four-stroke engine equipped with a catalyst could reduce the exposure. To reduce the exposure for the passenger on a sleigh an extension of the exhaust pipe may be effective.     

Occupational exposure assessment of phthalate esters in indoor and outdoor microenvironments

Phthalate esters(PAEs) are widely used as plasticizers in consumer products. PAEs are a group of environmental hormone which disrupts human and animals' endocrine systems. Different occupational groups are exposed to various levels of PAEs. In the present study, four typical occupational groups were chosen, including doctors, college teachers, college students, and drivers who worked in public traffic system. In order to understand the exposure levels to PAEs via inhalation, air samples were collected from multiple microenvironments including indoor and outdoor in Hangzhou to measure the gas and particle concentrations of six PAEs, together with time spent in different microenvironments of these four groups. A comprehensive PAEs exposure model was built to estimate the daily PAEs exposure through inhalation, oral and dermal pathways. The Monte Carlo simulation results show that doctors were exposed to the highest level of PAEs, and consequently had the highest health risk among these four occupational groups. In contrast, college students had the lowest health risk. By setting the exposure level of staying in residences as the baseline, doctors and drivers were two occupations exposed to high PAEs health risk. Di-(2-ethylhexyl) phthalate(DEHP) was the largest contributor among the six phthalates, posing moderate health risk(10-5–10-6) to every occupation. For traffic microenvironments alone, the total exposure levels for different transportation modes were in the descending order of busses, cars, cabs, tubes, motor bikes, and walking.     

Upscaling heterogeneity in aquifer reactivity via exposure-time concept: forward model

Reactive properties of aquifer solid phase materials play an important role in solute fate and transport in the natural subsurface on time scales ranging from years in contaminant remediation to millennia in dynamics of aqueous geochemistry. Quantitative tools for dealing with the impact of natural heterogeneity in solid phase reactivity on solute fate and transport are limited. Here we describe the use of a structural variable to keep track of solute flux exposure to reactive surfaces. With this approach, we develop a non-reactive tracer model that is useful for determining the signature of multi-scale reactive solid heterogeneity in terms of solute flux distributions at the field scale, given realizations of three-dimensional reactive site density fields. First, a governing Eulerian equation for the non-reactive tracer model is determined by an upscaling technique in which it is found that the exposure time of solution to reactive surface areas evolves via both a macroscopic velocity and a macroscopic dispersion in the artificial dimension of exposure time. Second, we focus on the Lagrangian approach in the context of a streamtube ensemble and demonstrate the use of the distribution of solute flux over the exposure time dimension in modeling two-dimensional transport of a solute undergoing simplified linear reversible reactions, in hypothetical conditions following prior laboratory experiments. The distribution of solute flux over exposure time in a given case is a signature of the impact of heterogeneous aquifer reactivity coupled with a particular physical heterogeneity, boundary conditions, and hydraulic gradient. Rigorous application of this approach in a simulation sense is limited here to linear kinetically controlled reactions.     

Are Bavarian Forests (southern Germany) at risk from ground-level ozone? Assessment using exposure and flux based ozone indices

Exposure and flux-based indices of O₃ risk were compared, at 19 forest locations across Bavaria in southern Germany from 2002 to 2005; leaf symptoms on mature beech trees found at these locations were also examined for O₃ injury. O₃ flux modelling was performed using continuously recorded O₃ concentrations in combination with meteorological and soil moisture data collected from Level II forest sites. O₃ measurements at nearby rural open-field sites proved appropriate as surrogates in cases where O₃ data were lacking at forest sites (with altitude-dependent average differences of about 10% between O₃ concentrations). Operational thresholds of biomass loss for both O₃ indices were exceeded at the majority of the forest locations, suggesting similar risk under long-term average climate conditions. However, exposure-based indices estimated higher O₃ risk during dry years as compared to the flux-based approach. In comparison, minor O₃-like leaf injury symptoms were detected only at a few of the forest sites investigated. Relationships between flux-based risk thresholds and tree response need to be established for mature forest stands for validation of predicted growth reductions under the prevailing O₃ regimes.     

Distribution of polybrominated diphenyl ethers in breast milk from North China: Implication of exposure pathways

The breast milk concentrations of polybrominated diphenyl ethers (PBDEs; sum of eight congeners: BDE-28, 47, 99, 100, 153, 154, 183 and 209) were determined (by high resolution gas chromatographic high resolution mass spectrometry) in samples from primiparous women collected in 2006 in Tianjin, China. Dietary and lifestyle habits of the participants were obtained by questionnaires. The median total PBDE concentration (including BDE-28, 47, 99, 100, 153, 154, 183) was 2500 pg g⁻¹ lipid weight, ranging from 1700 to 4500 pg g⁻¹ lipid weight. These levels were in the same range as those from Europe and Japan but much lower than those from North America. The congener profile in China was also different from other countries. The contribution of BDE-28 was around 15%, much higher than any other country, implying that a different Penta-BDE formulation might be used in the Chinese market. The lower ratio of the sum of BDE-47, 99, and 100 to the sum of BDE-153 and 154 suggested that Octa-products were in more demand in China. A significant correlation was found between a woman’s PBDE concentration and the time she used electronic appliances (h/d). This implies that electronics are a potential source of PBDEs to people. Inhalation or ingestion of particulate matter (such as dust) may also be an important exposure pathway. There was no significant correlation between the PBDE concentration and the consumption of meat, fish, and milk. Further research is needed to determine the specific contribution of each exposure route and their health effects.     

Skewed Riskscapes and Environmental Injustice: A Case Study of Metropolitan St. Louis

This article presents a case study of Toxics Release Inventory (TRI) air pollution exposure risks across metropolitan St. Louis. The first section critically reviews environmental justice research and related barriers to environmental risk management. Second, the paper offers a conventional analysis of the spatial patterns of TRI facilities and their surrounding census block group demographics for metropolitan St. Louis. Third, the article describes the use of an exposure risk characterization for 319 manufacturers and their air releases of more than 126 toxic pollutants. This information could lead to more practical resolutions of urban environmental injustices. The analysis of TRIs across metropolitan St. Louis shows that minority and low-income residents were disproportionately closer to industrial pollution sources at nonrandom significance levels. Spatial concentrations of minority residents averaged nearly 40% within one kilometer of St. Louis TRI sites compared to 25% elsewhere. However, one-fifth of the region's air pollution exposure risk over a decade was spatially concentrated among only six facilities on the southwestern border of East St. Louis. This disproportionate concentration of some of the greatest pollution risk would never be considered in most conventional environmental justice analyses. Not all pollution exposure risk is average, and the worst risks deserve more attention from environmental managers assessing and mitigating environmental injustices.     

Occupational risk from static magnetic fields of MRI scanners

The health care staff operating magnetic resonance imaging (MRI) scanners are exposed to static magnetic field of significant spatial heterogenity and high level of flux density—usually existing permanently during the shift. The personnel can also be exposed to pulses of magnetic field of high rate of rise/fall, so-called gradient fields, which exist only during examination of patients. The level of workers’ exposure depends both on the type of the magnet and on the ergonomical characteristic of design of the particular MRI scanner. This paper presents the current state of the art on occupational exposure to static magnetic field health effects, gaps in scientific data, MRI workers’ exposure characteristics, research needs, and suggestions for the exposure assessment protocol for future investigations.     

Practical aspects of occupational EMF exposure assessment

Electromagnetic fields exposure assessment methodology is briefly presented. The basic problems defined for the practical use of electromagnetic fields measurements and numerical calculations carried out for workers exposure assessment in real occupational situations are discussed. The examples of data from real workplace are presented, focusing: spatial distribution of electromagnetic fields affecting worker’s body, complex characteristics of the frequency content, workers activities/moving in the workplace, field impedance, etc. The situation when the use of calculations is required is discussed. The basic requirements for workers exposure assessment protocols are presented. The possible range of the use of internal and external measures of exposure level is also discussed.