The Pliofilm cohort is the most intensely studied group of workers chronically exposed to benzene. Information on this cohort has been the basis for regulations and/or guidelines for occupational and environmental exposure to benzene. Rinsky et al. (1986, 1987) and Crump and Allen (1984) developed different approaches for reconstructing the exposure history of each member of the group. The predicted levels of exposure, combined with the data on the incidence of disease, have been used to estimate benzene's carcinogenic potency. In this paper, recent information from worker interviews and historical records from the National Archives and elsewhere were used to evaluate the accuracy of prior exposure estimates and to develop better ones for the cohort. The following factors were accounted for: (1) uptake of benzene due to short-term, high-level exposure to vapors, (2) uptake due to background concentrations in the manufacturing building, (3) uptake due to contact with the skin, (4) morbidity and mortality data on workers in the Pliofilm process, (5) the installation of industrial hygiene engineering controls, (6) extraordinarily long work weeks during the 1940s, (7) data indicating that airborne concentrations of benzene were underestimated due to inaccurate monitoring devices and the lack of adequate field calibration mated due to inaccurate monitoring devices and the lack of adequate field calibration of these devices, and (8) likely effectiveness of respirators and gloves. Our estimates suggest that Crump and Allen (1984) overestimated the exposure of workers in some job classifications and underestimated others, and that Rinsky et al. (1981, 1986) almost certainly underestimated the exposure of nearly all workers. Airborne concentrations of benzene at the St. Marys facility during the years of its operation were found (on average) to be about half those of the two Akron facilities. Our analysis indicates that short-term, high-level exposure to benzene vapors and dermal exposure significantly increased (by about 25-50%) the total absorbed dose of benzene for some workers. One of the key findings was that, unlike prior analyses, the three facilities probably had significantly different airborne concentrations of benzene, especially during the 1940s and 1950s.

Attaining the National Ambient Air Quality Standard (NAAQS) for ozone (O 3

The U.S. Environmental Protection Agency has established a federal reference method (FRM) for ozone (O 3 ) and allowed for designation of federal equivalent methods (FEMs). However, the ethylene-chemiluminescence FRM for O 3 has been replaced by the UV photometric FEM by most state and local monitoring agencies because of its relative ease of operation. Accumulating evidence indicates that the FEM is prone to bias under the hot, humid, and stagnant conditions conducive to high O 3 formation. This bias may lead to overreporting hourly O 3 concentrations by as much as 20 -40 ppb. Measurement bias is caused by contamination of the O 3 scrubber, a problem that is not detected by dry air calibration. An adequate wet test has not been codified, although a procedure has been proposed for agency consideration. This paper includes documentation of laboratory tests quantifying specific interferant responses, collocated ambient FRM/FEM monitoring results, and smog chamber comparisons of the FRM and FEMs with alternative scrubber designs. As

A pilot study was conducted using an occupied, single-family test house in Columbus, OH, to determine whether a script-based protocol could be used to obtain data useful in identifying the key factors affecting air-exchange rate (AER) and the relationship between indoor and outdoor concentrations of selected traffic-related air pollutants. The test script called for hourly changes to elements of the test house considered likely to influence air flow and AER, including the position (open or closed) of each window and door and the operation (on/off) of the furnace, air conditioner, and ceiling fans. The script was implemented over a 3-day period (January 30-February 1, 2002) during which technicians collected hourly-average data for AER, indoor, and outdoor air concentrations for six pollutants (benzene, formaldehyde (HCHO), polycyclic aromatic hydrocarbons (PAH), carbon monoxide (CO), nitric oxide (NO), and nitrogen oxides (NO x )), and selected meteorological variables. Consistent with expectations, AER tended to increase with the number of open exterior windows and doors. The 39 AER values measured during the study when all exterior doors and windows were closed varied from 0.36 to 2.29 h À1 with a geometric mean (GM) of 0.77 h À1 and a geometric standard deviation (GSD) of 1.435. The 27 AER values measured when at least one exterior door or window was opened varied from 0.50 to 15.8 h À1 with a GM of 1.98 h À1 and a GSD of 1.902. AER was also affected by temperature and wind speed, most noticeably when exterior windows and doors were closed. Results of a series of stepwise linear regression analyses suggest that (1) outdoor pollutant concentration and (2) indoor pollutant concentration during the preceding hour were the ''variables of choice'' for predicting indoor pollutant concentration in the test house under the conditions of this study. Depending on the pollutant and ventilation conditions, one or more of the following variables produced a small, but significant increase in the explained variance (R 2 -value) of the regression equations: AER, number and location of apertures, wind speed, air-conditioning operation, indoor temperature, outdoor temperature, and relative humidity. The indoor concentrations of CO, PAH, NO, and NO x were highly correlated with the corresponding outdoor concentrations. The indoor benzene concentrations showed only moderate correlation with outdoor benzene levels, possibly due to a weak indoor source. Indoor formaldehyde concentrations always exceeded outdoor levels, and the correlation between indoor and outdoor concentrations was not statistically significant, indicating the presence of a strong indoor source.

Multibillion-dollar strategies control ambient air ozone (O 3 ) levels in the United States, so it is essential that the measurements made to assess compliance with regulations be accurate. The predominant method employed to monitor O 3 is ultraviolet (UV) photometry. Instruments employ a selective manganese dioxide or heated silver wool "scrubber" to remove O 3 to provide a zero reference signal. Unfortunately, such scrubbers remove atmospheric constituents that absorb 254-nm light, causing measurement interference. Water vapor also interferes with the measurement under some circumstances. We report results of a 3-month field test of two new instruments designed to minimize interferences (2B Technologies model 211; Teledyne-API model 265E) that were operated in parallel with a conventional Thermo Scientific model 49C O 3 monitor. The field test was hosted by the Houston Regional Monitoring Corporation (HRM). The model 211 photometer scrubs O 3 with excess nitric oxide (NO) generated in situ by photolysis of added nitrous oxide (N 2 O) to provide a reference signal, eliminating the need for a conventional O 3 scrubber. The model 265E analyzer directly measures O 3 -NO chemiluminescence from added excess NO to quantify O 3 in the sample stream. Extensive quality control (QC) and collocated monitoring data are assessed to evaluate potential improvements to the accuracy of O 3 compliance monitoring.Implications: Two new-technology ozone monitors were compared with a conventional monitor under field conditions. Over 3 months the conventional monitor reported more exceedances of the current standard than the new instruments, which could potentially result in an area being misjudged as "nonattainment." Instrument drift can affect O 3 data accuracy, and the same degree of drift has a proportionally greater compliance effect as standard stringency is increased. Enhanced data quality assurance and data adjustment may be necessary to achieve the improved accuracy required to judge compliance with tighter standards.