Estimating airborne benzene exposures from air monitoring data for mineral spirits

"Low aromatics" vs. "regular" mineral spirits differ substantially in their aromatic hydrocarbon content. Mineral spirits contain benzene and other compounds that boil at temperatures below the cited boiling point range of 300 ° to 415 °F. Available published information shows that until at least 2000, the benzene content of regular mineral spirits was typically 0.1% wt/wt and at times could have been 1.0% wt/wt. The present analysis accounts for benzene's higher volatility compared to mineral spirits as a whole and applies thermodynamic principles to estimate benzene vapor exposure as a subset of measured exposure to total hydrocarbons generated by the evaporation of mineral spirits. For a scenario in which the bulk mineral spirits only partially evaporate, this analysis explains the error in assuming that the mole fraction of benzene to "everything else" is the same in the vapor and liquid phases. It is shown that for a given concentration of total hydrocarbon vapor, the benzene vapor concentration can be more than 65-fold greater during mineral spirits evaporation compared to after all the mineral spirits has evaporated. In turn, it is reasonable to expect that during the use of regular mineral spirits, containing benzene typically at 0.1% wt/wt (as applies to usage prior to 2000), benzene vapor exposures could have exceeded 1 ppm even though the mineral spirits vapor exposure did not exceed 100 ppm, the ACGIH? TLV? time-weighted average (TWA) value for mineral spirits. The same analysis can be applied to current petrochemical products, such as toluene, that contain benzene and for which the required physico-chemical information is available. The analysis provides evidence that the material safety data sheet (MSDS) for a petrochemical product containing benzene at less than 0.1% wt/wt should, pursuant to Hazard Communication Standard requirements, identify the benzene as a hazardous ingredient.     

Estimating cancer risk from outdoor concentrations of hazardous air pollutants in 1990

A public health concern regarding hazardous air pollutants (HAPs) is their potential to cause cancer. It has been difficult to assess potential cancer risks from HAPs, due primarily to lack of ambient concentration data for the general population. The Environmental Protection Agency's Cumulative Exposure Project modeled 1990 outdoor concentrations of HAPs across the United States, which were combined with inhalation unit risk estimates to estimate the potential increase in excess cancer risk for individual carcinogenic HAPs. These were summed to provide an estimate of cancer risk from multiple HAPs. The analysis estimates a median excess cancer risk of 18 lifetime cancer cases per 100,000 people for all HAP concentrations. About 75% of estimated cancer risk was attributable to exposure to polycyclic organic matter, 1,3-butadiene, formaldehyde, benzene, and chromium. Consideration of some specific uncertainties, including underestimation of ambient concentrations, combining upper 95% confidence bound potency estimates, and changes to potency estimates, found that cancer risk may be underestimated by 15% or overestimated by 40-50%. Other unanalyzed uncertainties could make these under- or overestimates larger. This analysis used 1990 estimates of concentrations and can be used to track progress toward reducing cancer risk to the general population.     

Estimating changes in river faecal coliform loading using nonparametric multiplicative regression

Faecal coliform (FC) concentration was monitored weekly in the Tangipahoa River over an eight year period. Available USGS discharge and precipitation data were used to construct a nonparametric multiplicative regression (NPMR) model for both forecasting and backcasting of FC density. NPMR backcasting and forecasting of FC allowed for estimation of concentration for any flow regime. During this study a remediation effort was undertaken to improve disinfection systems of contributing municipal waste water treatment plants in the watershed. Time-series analysis of FC concentrations demonstrated a drop in FC levels coinciding with remediation efforts. The NPMR model suggested the reduction in FC levels was not due to climate variance (i.e. discharge and precipitation changes) alone. Use of the NPMR method circumvented the need for construction of a more complex physical watershed model to estimate FC loading in the river. This method can be used to detect and estimate new discharge impacts, or forecast daily FC estimates.     

Estimating the effects of energy imbalance on changes in body weight in children

BACKGROUND: Estimating changes in weight from changes in energy balance is important for predicting the effect of obesity prevention interventions. OBJECTIVE: The objective was to develop and validate an equation for predicting the mean weight of a population of children in response to a change in total energy intake (TEI) or total energy expenditure (TEE). DESIGN: In 963 children with a mean (+/-SD) age of 8.1 +/- 2.8 y (range: 4-18 y) and weight of 31.5 +/- 17.6 kg, TEE was measured by using doubly labeled water. Log weight (dependent variable) and log TEE (independent variable) were analyzed in a linear regression model with height, age, and sex as covariates. It was assumed that points of dynamic balance, called "settling points," occur for populations wherein energy is in balance (TEE = TEI), weight is stable (ignoring growth), and energy flux (EnFlux) equals TEE. RESULTS: TEE (or EnFlux) explained 74% of the variance in weight. The unstandardized regression coefficient was 0.45 (95% CI: 0.38, 0.51; R(2) = 0.86) after including covariates. Conversion into proportional changes (time(1) to time(2)) gave the equation (weight(2)/weight(1)) = (EnFlux(2)/EnFlux(1))(0.45). In 3 longitudinal studies (n = 212; mean follow-up of 3.4 y), the equation predicted the mean follow-up measured weight to within 0.5%. CONCLUSIONS: The relation of EnFlux with weight was positive, which implied that a high TEI (rather than low physical activity and low TEE) was the main determinant of high body weight. Two populations of children with a 10% difference in mean EnFlux would have a 4.5% difference in mean weight.     

Estimating long-term average particulate air pollution concentrations: application of traffic indicators and geographic information systems

BACKGROUND: As part of a multicenter study relating traffic-related air pollution with incidence of asthma in three birth cohort studies (TRAPCA), we used a measurement and modelling procedure to estimate long-term average exposure to traffic-related particulate air pollution in communities throughout the Netherlands; in Munich, Germany; and in Stockholm County, Sweden. METHODS: In each of the three locations, 40-42 measurement sites were selected to represent rural, urban background and urban traffic locations. At each site and fine particles and filter absorbance (a marker for diesel exhaust particles) were measured for four 2-week periods distributed over approximately 1-year periods between February 1999 and July 2000. We used these measurements to calculate annual average concentrations after adjustment for temporal variation. Traffic-related variables (eg, population density and traffic intensity) were collected using Geographic Information Systems and used in regression models predicting annual average concentrations. From these models we estimated ambient air concentrations at the home addresses of the cohort members. RESULTS: Regression models using traffic-related variables explained 73%, 56% and 50% of the variability in annual average fine particle concentrations for the Netherlands, Munich and Stockholm County, respectively. For filter absorbance, the regression models explained 81%, 67% and 66% of the variability in the annual average concentrations. Cross-validation to estimate the model prediction errors indicated root mean squared errors of 1.1-1.6 microg/m for PM(2.5) and 0.22-0.31 *10(-5) m for absorbance.CONCLUSIONS: A substantial fraction of the variability in annual average concentrations for all locations was explained by traffic-related variables. This approach can be used to estimate individual exposures for epidemiologic studies and offers advantages over alternative techniques relying on surrogate variables or traditional approaches that utilize ambient monitoring data alone.     

Cardiac arrhythmias and heart rate changes in prolonged hyperbaric air exposures

Daily resting and exercise electrocardiograms from 81 healthy subjects taking part in eight different air saturation chamber experiments at depths of 2-132 ft sea water gauge (fswg) were recorded and interpreted. Scalar and planar characteristics were measured and analyzed in addition to noting changes in rhythm. Of the measured variables, only the heart rate and QT-interval changed significantly in the majority of exposures. Heart rate decrements of 14%-23% were observed, generally with normalization after several days at depth, and in some cases a rebound immediately postexposure. The observed increase in QT-interval can be explained entirely by the bradycardia, which seems to be due to a combination of pressure, hyperoxia, and a chamber effect. Further distinction among these factors was not possible. Associated with the decrements in heart rate were asymptomatic supraventricular arrhythmias, generally AV-nodal escape rhythms or beats, in 10% of the subjects. One incident of symptomatic ventricular tachycardia was noted 20 h after surfacing during an exercise test. Otherwise, only infrequent, isolated premature ventricular beats were detected at depth, but were not more frequent than in the predive periods. These findings are consistent with the premise that exposure to hyperbaric air and other nitrogen-oxygen mixtures causes an increase in parasympathetic tone of sufficient magnitude to cause cardiac arrhythmias. That autonomic imbalance in diving activities may cause more malignant arrhythmias is discussed.     

模拟大气污染所致大鼠气管的病理学改变

目的 探讨大气污染物对大鼠气管的病理学改变。方法80只Wistar大鼠（体重180～220g）随机分为4组，即1个对照组和3个实验组（低、中、高剂量组）。实验组大鼠分别注入含7．5，15或30mg的总悬浮颗粒物（TSP）生理盐水混悬液1ml，然后静式吸入浓度分别为8和5，16和10，32和20mg/m^3的SO2和NO2的空气混合气，每天2h，连续染毒7d。对照组大鼠注入1ml生理盐水并吸入一般空气。电镜下观察大鼠气管的超微结构变化。结果气管上皮纤毛粘连、紊乱、倒伏及鳞状化生，上皮细胞空泡变性，并可见新生的纤毛上皮细胞。结论大气污染物可引起大鼠气管纤毛的摆动功能减弱及丧失，导致其排出功能障碍。     

Repolarization changes induced by air pollution in ischemic heart disease patients

Epidemiologic studies report associations between particulate air pollution and cardiovascular morbidity and mortality, but the underlying pathophysiologic mechanisms are still unclear. We tested the hypothesis that patients with preexisting coronary heart disease experience changes in the repolarization parameters in association with rising concentrations of air pollution. A prospective panel study was conducted in Erfurt, East Germany, with 12 repeated electrocardiogram (ECG) recordings in 56 males with ischemic heart disease. Hourly particulate and gaseous air pollution and meteorologic data were acquired. The following ECG parameters reflecting myocardial substrate and vulnerability were measured: QT duration, T-wave amplitude, T-wave complexity, and variability of T-wave complexity. Fixed effect regression analysis was used adjusting for subject, trend, weekday, and meteorology. The analysis showed a significant increase in QT duration in response to exposure to organic carbon; a significant decrease in T-wave amplitude with exposure to ultrafine, accumulation mode, and PM2.5 particles (particles < 2.5 microm in aerodynamic diameter); and a corresponding significant increase of T-wave complexity in association with PM2.5 particles for the 24 hr before ECG recordings. Variability of T-wave complexity showed a significant increase with organic and elemental carbon in the same time interval. This study provides evidence suggesting an immediate effect of air pollution on repolarization duration, morphology, and variability representing myocardial substrate and vulnerability, key factors in the mechanisms of cardiac death.     

Meeting report: Estimating the benefits of reducing hazardous air pollutants--summary of 2009 workshop and future considerations

Background

Quantifying the benefits of reducing hazardous air pollutants (HAPs, or air toxics) has been limited by gaps in toxicological data, uncertainties in extrapolating results from high-dose animal experiments to estimate human effects at lower doses, limited ambient and personal exposure monitoring data, and insufficient economic research to support valuation of the health impacts often associated with exposure to individual air toxics.

Objectives

To address some of these issues, the U.S. Environmental Protection Agency held the Workshop on Estimating the Benefits of Reducing Hazardous Air Pollutants (HAPs) in Washington, DC, from 30 April to 1 May 2009.

Discussion

Experts from multiple disciplines discussed how best to move forward on air toxics benefits assessment, with a focus on developing near-term capability to conduct quantitative benefits assessment. Proposed methodologies involved analysis of data-rich pollutants and application of this analysis to other pollutants, using dose–response modeling of animal data for estimating benefits to humans, determining dose-equivalence relationships for different chemicals with similar health effects, and analysis similar to that used for criteria pollutants. Limitations and uncertainties in economic valuation of benefits assessment for HAPS were discussed as well.

Conclusions

These discussions highlighted the complexities in estimating the benefits of reducing air toxics, and participants agreed that alternative methods for benefits assessment of HAPs are needed. Recommendations included clearly defining the key priorities of the Clean Air Act air toxics program to identify the most effective approaches for HAPs benefits analysis, focusing on susceptible and vulnerable populations, and improving dose–response estimation for quantification of benefits.     

空气供气循环紧闭麻醉环路氧浓度变化规律研究

目的 探讨空气循环紧闭麻醉呼吸环路内氧浓度变化规律.方法 ASA Ⅰ～Ⅱ级腹部择期手术患者和健康志愿者各20例,根据供气的不同,将手术患者和志愿者相应地分为纯氧对照组和空气实验组,每组各10例 以空气替代纯氧供应,每分钟记录一次氧浓度,手术患者环路内最低浓度不低于25%,低于25%直到最低耐受氧浓度段试验采用健康志愿者.结果 手术组和志愿者组在空气供气下氧浓度随时间延长逐渐下降,与对照组相比,有显著的统计学差异（P≤0.01）.手术实验组氧浓度与时间呈正相关（r=0.9999,t=894.381,P≤0.01）,直线回归方程是y=-3.0695x＋84.40 志愿者实验组氧浓度与时间也呈正相关（r=0.9899,t=28.001,P≤0.01）,直线回归方程是y=-3.0967x＋41.447.结论 空气循环紧闭麻醉呼吸环路内氧浓度随时间延长而降低,且氧浓度与时间的变化呈直线相关.     

Estimating the effect of air pollution from a coal-fired power station on the development of children's pulmonary function

Using geographical information systems (GIS) tools, the present study analyzed the association between children's lung function development and their long-term exposure to air pollution. The study covered the cohort of 1492 schoolchildren living in the vicinity of a major coal-fired power station in the Hadera sub-district of Israel. In 1996 and 1999, the children underwent subsequent pulmonary function tests (PFT) (forced vital capacity (FVC) and forced expiratory volume during the first second (FEV(1))), and the children's parents completed a detailed questionnaire on their health status and household characteristics. A negative association was found between changes in the results of PFT and the estimated individual levels of air pollution. A sensitivity test revealed a FEV(1) decline from -4.3% for the average pollution level to -10.2% for the high air pollution level. The results of a sensitivity test for FVC were found to be similar. Association with the reported health status was found to be insignificant. As we conclude, air pollution from a coal-fired power station, although not exceeding local pollution standards, had a negative effect on children's lung function development. As argued, previous studies carried out in the region failed to show the above association because they were based on zone approaches that assign average concentration levels of air pollutants to all individuals in each zone, leading to a misclassification bias of individual exposure.     

Estimating cumulative ambient concentrations of air pollutants: description and precision of methods used for an epidemiological study

Methods for estimating cumulative ambient air pollution concentrations for individuals enrolled in an epidemiological cohort study are described and studied. Monthly interpolations from fixed-site monitoring stations in California to zip code centroids were used. The precision of the interpolation methods for total suspended particulates and ozone was assessed, and fixed-site monitoring stations were used in turn as receptor sites. Actual versus interpolated 2-y mean concentrations did not differ significantly and were correlated with a Pearson correlation coefficient of .78 for total suspended particulates and .87 for ozone. The impact of the change from monitoring total oxidants to ozone on oxidant/ozone cumulations was evaluated, and monthly mean concentrations for total oxidants were compared with ozone for 435 station months during which both pollutants were measured simultaneously. Average concentrations did not differ significantly and were highly correlated (r = 0.94). Exceedance frequency statistics, which averaged slightly higher for ozone than for total oxidants, were also highly correlated.     

Respiratory symptoms and air pollution changes in children: the Gardanne Coal-Basin Study

The influence of daily changes in sulfur dioxide (SO2) levels on the induction of respiratory symptoms was studied during the 1983-1984 winter in 450 children, aged 9 to 11 yr, living in the Gardanne coal-basin, France. In this area, SO2 originates mainly from a coal-fueled power plant. The mean SO2 level during the winter was 22 micrograms/m3 in low-pollution areas and 93 micrograms/m3 in polluted areas, with daily SO2 levels up to 356 micrograms/m3. Children completed a daily diary about respiratory symptoms. In the polluted communities only we demonstrated a significant association between daily SO2 levels (after controlling for temperature and respirable particle variations) and prevalence of upper and lower respiratory symptoms. However, in each polluted town, and for each respiratory symptom, there was no evidence for either a latency period or a delay in the effects of pollutants. Mean daily temperature was also closely correlated with upper and lower respiratory symptoms in most of the polluted and some low-pollution communities. In a second step, the prevalence of respiratory symptoms in each town was compared, during two 2-wk periods, with air pollution levels; higher prevalences were found during the pollution period. In conclusion, moderate daily changes in SO2 levels induce a significant but transient increase in the prevalence of respiratory symptoms in children.     

Estimating the return-on-investment from changes in employee health risks on the Dow Chemical Company's health care costs

OBJECTIVE: We sought to estimate the impact of corporate health-management and risk-reduction programs for The Dow Chemical Company by using a prospective return-on-investment (ROI) model. METHODS: The risk and expenditure estimates were derived from multiple regression analyses showing relationships between worker demographics, health risks, and medical expenditures. RESULTS: A "break-even" scenario would require Dow to reduce each of 10 population health risks by 0.17% points per year over the course of 10 years. More successful efforts at reducing health risks in the population would produce a more significant ROI for the company. CONCLUSIONS: Findings from this study were incorporated into other components of a business case for health and productivity management, and these supported continued investments in health improvement programs designed to achieve risk reduction and cost savings.     

The experimental morphofunctional changes in the body under the influence of dry environmental air

Analysis of morphological changes in organs, tissues and cells of animal organisms (white rats) is presented in interrelations with shifts in somatometric parameters, fluctuations in water exchange induced by the decreased content of diluted liquid vapours in the air. On the basis of studies results the leading role of low humidity of the environment in the development of changes of the dehydration syndrome type has been proved.     

Mortality from asthma and chronic bronchitis associated with changes in sulfur oxides air pollution

Death certificates issued in Yokkaichi, Japan, during the 21 yr from 1963 until 1983 were surveyed to determine the relationship between changes in air pollution and mortality due to bronchial asthma and chronic bronchitis. The following results were obtained. In response to worsening air pollution, mortality for bronchial asthma and chronic bronchitis began to increase. Mortality due to bronchial asthma decreased immediately in response to improvement of pollution, whereas mortality due to chronic bronchitis decreased to the level in the control area 4 to 5 yr after the concentration of sulfur dioxide (SO2) began to satisfy the ambient air quality standard. In the polluted area, mortality due to bronchial asthma in subjects who were 20 yr of age was higher during the period in which higher concentrations of sulfur oxides were prevalent.     

Impact of short weather changes on the population's health risk from ambient air pollution

The paper considers the negative impact of weather changes in combination with the altered quality of ambient air on the economic and social spheres of society and on the population's health. It describes experience in assessing a possible damage to the health of the Moscow population from exposure to elevated concentrations of ambient air pollutants (suspended matter, nitrogen and sulfur dioxides, carbon oxide). The results of assessment simulation of dissemination of chemicals contained in the emission from the Moscow heat-and-power objects under poor weather conditions are presented.