Full-shift Exposure Research Articles

Assessing reasonable worst-case full-shift exposure levels from data of variable quality.

Exposure assessors involved in regulatory risk assessments often need to estimate a reasonable worst-case full-shift exposure level from very limited exposure information. Full-shift exposure data of very high quality are rare. A full-shift value can also be calculated from (short term) task-based values, either derived from measured data or from models. The most simple option is to use the task based exposure levels as the full-shift value. A second option is to calculate a time-weighted average (TWA), using (reasonable worst case) estimates of the duration and the exposure level of the relevant tasks. The third option is to use a Monte Carlo analysis with estimated input distributions for exposure level and duration of exposure. If an estimated distribution of respiratory volume is also included, this leads to a distribution of inhaled amounts. The 90th percentile of such a distribution is generally substantially lower than the fixed point estimates calculated using high end values for each parameter. This technique can thus prevent unnecessary conservative estimates in risk assessment. The output distribution can also be used as valuable input to the risk management process, because it provides information on probabilities of exposure levels, that can influence the cost-benefit analysis of the risk management process. Finally, the sensitivity analysis of Monte Carlo simulation can give guidance for further studies to increase the accuracy of the exposure assessment.

Hydrocarbon solvent exposure data: compilation and analysis of the literature.

An occupational exposure database for hydrocarbon solvent end-use applications was constructed from the published literature. The database provides exposure assessment information for such purposes as regulatory risk assessments, support of industry product stewardship initiatives, and identification of applications in which limited exposure data are available. It is quantitative, documented, and based on credible data. Approximately 350 articles containing quantitative hydrocarbon solvent exposure data were identified using a search of computer databases of published literature. Many articles did not report sufficient details of the exposure data for inclusion in the database (e.g., full-shift exposure or task-based exposure data). Others were excluded because only limited summary statistics were provided, which precluded statistical analysis of the data (e.g., arithmetic mean concentration presented, but no sample number). Following evaluation, 16,880 hydrocarbon solvent exposure measurements from 99 articles were entered into a database for analysis. Methods used to identify and evaluate published solvent exposure data are described along with more detailed analysis of worker exposure to hydrocarbon solvents in three major end-use applications: painting and coating, printing, and adhesives. Solvent exposures were evaluated against current ACGIH threshold limit values (TLVs) and trends were identified. Limited quantitative data are available prior to 1970. In general, reported hydrocarbon solvent exposures decreased fourfold from 1960 to 1998, were below the TLVs applicable to specific hydrocarbon solvents at the time, and on average have been below 40% of the TLV since 1980. The database already has proved valuable; however, the utility of published exposure data could be further improved if authors consistently reported essential data elements and supporting information.

An Evaluation of Worker Lead Exposures and Cleaning Effectiveness During Removal of Deteriorated Lead-Based Paint

We evaluated worker lead exposures and cleaning effectiveness during initial cleanup of 19th-century buildings with highly deteriorated lead-based paint. Eighteen rooms of similar size and condition in two university-owned buildings were selected for a pilot project to compare three methods for removing loose paint, paint chips, and dust. The methods used were: dry scraping followed by dry sweeping (no engineering or work practice controls); wet scraping and high-efficiency particulate air (HEPA) vacuuming; and the latter method with the addition of a portable HEPA-filtered exhaust fan in the room providing about 40 air changes per hour. The final step for all methods was wet-mopping once with tri-sodium phosphate solution. During a single day 18 rooms were cleaned; each of three two-person work crews cleaned six rooms, two with each method. Air and surface samples were collected before, during, and after cleaning. All of the methods were potentially hazardous to workers: 44 percent of the method-based exposures (range: 5.0-360 micrograms/m3) and one of five full-shift exposures exceeded the OSHA PEL (range 9.4-110 micrograms/m3). Lowest worker exposures were during the wet scraping and vacuuming method (mean: 24 micrograms/m3). Providing general ventilation in rooms did not reduce worker exposures and appeared to increase them (mean: 73 micrograms/m3). Overall, the mean floor surface lead levels were reduced 50 percent after cleaning (from 2,600 to 1,300 micrograms/ft2), but the effectiveness of the three methods in reducing floor lead levels did not differ significantly. Overall, the method, mean paint lead concentration, pre-cleaning surface lead concentration, and work crew were significantly associated with the mean worker exposures during cleaning (p = 0.023), but not with the post-cleaning surface lead concentrations (p = 0.13).

Characterization of Extremely Low Frequency Magnetic Field Exposures of Office Workers

Abstract The purpose of this study is to present results of an extremely low frequency magnetic field exposure assessment performed in a large office building environment. The extremely low frequency magnetic field assessment strategy included an evaluation of full-shift personal exposure for building occupants, a determination of average work area magnetic fields, and magnetic field characterizations of sources within each work area. An employee questionnaire regarding daily utilization patterns of workplace magnetic field sources was also used to help interpret exposure information. Magnetic field exposures were determined using EMDEX magnetic field exposure meters. For personal magnetic field characterization, each participant wore the monitor for a full shift, and office area magnetic fields were determined as the average of five equally spaced measurements. In situ source characterization included measuring magnetic fields at 30 and 50 cm from pieces of electrical equipment. 259 employees in the buil...

Worker Lead Exposures During Renovation of Homes with Lead-Based Paint

Abstract We evaluated lead exposures among full-time home renovators and part-time volunteers working primarily in pre-1960 homes with lead-based paint. Potentially hazardous lead exposures were measured during two tasks: exterior dry scraping and wet scraping. Maximum exposures were 120 and 63 μg/m3, respectively. Exposures during other tasks, including general repair, weatherization, exterior scraping/painting (mostly applying new paint), window replacement, demolition, and plumbing, were low (range: 0.1 to 16 μg/m3), as were all 13 full-shift personal exposures [geometric mean (GM) = 3.6 μg/m3; range: 0.2 to 12 μg/m3]. Blood lead levels for full-time workers ranged up to 17.5 μg/dl, with a GM of 5.2 μg/dl; the GM for volunteers was 3.2 μg/dl. All of the paint samples collected from work surfaces had detectable amounts of lead (GM = 1.05%), with 65 percent (32) of the work surfaces tested having an average lead concentration of >0.5 percent. Paired sampling results indicate that chemical spot test kits,...

Risk factors for sensitisation and respiratory symptoms among workers exposed to acid anhydrides: a cohort study.

OBJECTIVES: To examine the relation between exposure to acid anhydrides and the risk of developing immediate skin prick test responses to acid anhydride human serum albumin (AA-HSA) conjugates or work...

Exposure levels and determinants of inhalable dust exposure in bakeries

The study's objectives were to measure full-shift exposure to inhalable dust in bakeries and define the determinants of full-shift exposure. Inhalable dust was measured gravimetrically. Ninety-six bakery workers, employed in seven different bakeries, participated in the study. Two side-by-side full-shift inhalable dust samples were obtained from each study participant on a single occasion. Samples were collected on 18 days selected at random. During the entire sampling period, bakers were observed and information on 14 different tasks was recorded at 15 min intervals. Other production characteristics were also recorded for each sampling day. These task and production variables were used in statistical modelling to identify significant predictors of exposure. The mean full-shift inhalable dust exposure was 8.2 mg/m3 (range: 0.1–110 mg/m3). A regression model explained 79% of the variability in exposure. The model indicated that tasks such as weighing, pouring and operating dough-brakers and reversible sheeters increased the exposure, while packing, catching and decorating decreased the exposure. Bread and bun production lines were associated with increased full-shift inhalable dust exposure, while cake production and substitution of dusting with the use of divider oil were associated with decreased exposure. Production tasks and characteristics are strong predictors of personal full-shift exposures to flour dust among bakers; these can be altered to reduce exposure levels.

EXPOSURE LEVELS AND DETERMINANTS OF INHALABLE DUST EXPOSURE IN BAKERIES

The study's objectives were to measure full-shift exposure to inhalable dust in bakeries and define the determinants of full-shift exposure. Inhalable dust was measured gravimetrically. Ninety-six bakery workers, employed in seven different bakeries, participated in the study. Two side-by-side full-shift inhalable dust samples were obtained from each study participant on a single occasion. Samples were collected on 18 days selected at random. During the entire sampling period, bakers were observed and information on 14 different tasks was recorded at 15 min intervals. Other production characteristics were also recorded for each sampling day. These task and production variables were used in statistical modelling to identify significant predictors of exposure. The mean full-shift inhalable dust exposure was 8.2 mg/m3 (range: 0.1–1 10 mg/m3). A regression model explained 79% of the variability in exposure. The model indicated that tasks such as weighing, pouring and operating dough-brakers and reversible sheeters increased the exposure, while packing, catching and decorating decreased the exposure. Bread and bun production lines were associated with increased full-shift inhalable dust exposure, while cake production and substitution of dusting with the use of divider oil were associated with decreased exposure. Production tasks and characteristics are strong predictors of personal full-shift exposures to flour dust among bakers; these can be altered to reduce exposure levels. © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

Exposure assessment in occupational epidemiology: measuring present exposures with an example of a study of occupational asthma.

The aim of the present paper is to present a comprehensive review of the issues involved in exposure assessment for occupational epidemiology studies and to provide an example. Exposure assessment for occupational epidemiology studies is becoming more quantitatively refined. This paper discusses important issues that need to be taken into account for exposure assessment, with particular reference to occupational asthma. It discusses issues such as survey design, data collection, the effect of measurement error and data interpretation. It presents recently developed methodology to evaluate exposure variability and its effect on the attenuation of risk estimates. It also presents methodology to control for such variability. It uses examples from a recent cohort study of flour millers and bakers. This example shows various characteristics of exposure and demonstrates that various measures of exposure, such as peak and full-shift exposure measurements, are regularly correlated, which has consequences for the analyses of exposure-response relationships. This paper stresses the importance of the recognition and evaluation of exposure variability and its effect on risk estimates and shows that with different exposure grouping schemes, different health risk estimates can be obtained. Quantitative exposure assessment is generally difficult, time-consuming and expensive and many issues need to be taken into account, but it can be rewarding and has become an absolute necessity for many occupational epidemiology studies. Evaluation of components of exposure variance is absolutely necessary. Exposure variability could lead to serious attenuation of risk estimates.

Carbon Monoxide Poisoning Related to the Indoor Use of Propane-Fueled Forklifts in Colorado Workplaces

Abstract The Colorado Department of Public Health and Environment (CDPHE) measured area carbon monoxide concentrations at three separate workplaces where workers had experienced acute carbon monoxide poisoning related to the indoor use of propane-fueled fork-lifts. Follow-up investigations were conducted at two of these workplaces where full-shift carbon monoxide exposure and end-exhaled carbon monoxide concentrations were measured to estimate carboxyhemoglobin concentrations. Draeger dataloggers equipped with carbon monoxide sensors were used to measure full-shift personal exposure and area airborne carbon monoxide concentrations. The dataloggers were also used to measure preshift and postshift end-exhaled carbon monoxide concentrations, which were then used to calculate carboxyhemoglobin concentrations. At the first workplace, a beverage distributing warehouse using two propane-fueled Nissan forklifts, carbon monoxide exposures ranged from 25 to 68 ppm (mean = 44 ppm) as work shift time-weighted average...

Exposure to acid anhydrides in three resin and one cushioned flooring manufacturing plants

Acid anhydrides are reactive organic chemicals of low molecular weight which cause occupational asthma. No previous research on the relationship between exposure to these chemicals and respiratory sensitization and development of occupational asthma has been reported. A retrospective cohort study was carried out in four factories (three alkyd resin factories and one cushioned flooring factory) to investigate the nature of exposure-response relationships for sensitization to phthalic anhydride (PA), trimellitic anhydride (TMA) and maleic anhydride (MA). This paper describes the results of full-shift and task-specific exposure measurements. Exposure to PA was low in relation to the Occupational Exposure Standard (OES). The highest full-shift PA exposures occurred among resin operators in the resin factory that used solid PA as compared to other resin factories where liquid PA was used. Arithmetic mean exposure levels to TMA and MA in the resin factories were well below their respective OESs. Short-term high exposures occurred during loading of acid anhydrides into the reactors and sampling and testing of the resin. Relatively high full-shift exposure to TMA occurred in the cushioned flooring factory, although no high peak exposures were detected.

Exposure to air contaminants in chicken catching.

A cross-sectional study of chicken catchers was carried out by personal sampling of air contaminants. The catchers used either the drawer method (DM) or truck method (TM) for loading chickens into cages. DM catchers were exposed to higher concentrations of hazardous substances than TM catchers, except for ammonia. In terms of geometric means total dust concentrations were 11.3 mg/m3 (DM catchers) and 8.1 mg/m3 (TM catchers). Full-shift dust exposure exceeded the Danish occupational exposure limit (OEL) of 3 mg/m3 for organic dust by at least a factor of 2. From paired personal sampling data the concentration of respirable dust ranged from 18% to 28% of the total dust concentration. The average exposure level to bacterial endotoxin in total dust at 82 ng/m3 for DM catchers and 42 ng/m3 for TM catchers exceeded a limit of 10 ng/m3 recommended for poultry processing industry workers in the United States. Endotoxin content of airborne dust averaged 6.5 +/- 4.9 ng/mg. Exposure to microorganisms was determined by microscopy (total count) and by culturing (viable count). The geometric means for total count (microorganisms/m3) were 7.0 x 10(8) (DM catchers) and 4.9 x 10(8) (TM catchers) and for viable count 3.2 x 10(7) cfu/m3 (DM catchers) and 1.4 x 10(7) cfu/m3 (TM catchers). The ratio of microorganisms counted by microscopy to levels of viable microorganisms ranged from 5 to 200, implying a strong underestimation of exposure levels from viable counts alone. It was concluded that Danish chicken catchers were exposed beyond recommended limits for the air contaminants evaluated.(ABSTRACT TRUNCATED AT 250 WORDS)

60 hertz magnetic field exposure assessment for an investigation of leukemia in telephone lineworkers

The purpose of this paper is to present the assessment of magnetic field exposure conducted as a part of a nested case-control investigation of leukemia mortality in telephone lineworkers. For the purposes of exposure classification, telephone company jobs were initially divided into two classes: those with potential for working in an electric environment, referred to as linework jobs, and those not working in an electric environment, referred to as nonlinework jobs. Linework jobs were further divided into the following four categories: outside plant technicians (OPT), installation/maintenance/repair (IMR) technicians, central office technicians (COT), and cable splicing technicians (CST). These job groupings were based on similarity of work tasks and exposure environments. Emdex data-logging dosimeters were used to measure personal exposures to ELF magnetic fields for 204 telephone company workers. Three general classes of exposure indices were calculated for each exposure record: measures of central tendency, measures of peak or maximum exposure, and measures of exposure variability. CSTs had the highest full-shift mean and median exposure, 4.3 and 3.2 mG, respectively. CSTs also ranked the highest, with average peak, average 95th percentile, and average time above background equal to 99.2 mG, 11.1 mG, and 156 min, respectively. In addition, the results suggest the OPT and IMR technicians have exposures similar to nonlineworkers. Exposure classifications, therefore, which misclassify all lineworkers into one "telephone lineworker" job grouping are not appropriate and future studies should concentrate on cable splicing technicians.

Factors Affecting Worker Exposures to Metal-Working Fluids During Automotive Component Manufacturing

Abstract A two-stage personal impactor was used to collect fullshift exposure measurements of metal-working fluid exposures from workers in three automotive component manufacturing facilities. The 403 workers exposed to metal-working fluid in machining and grinding operations had an average total particulate exposure of 706 μg/m3 (standard error = 21 μg/m3). For a subset of 309 workers, information on factors that might influence the exposure level was also collected. This information included the metal-working fluid type, the machine type, the presence of local exhaust, the degree of machine enclosure, the age of the machine, the distance of the worker from the machine, and the indoor and outdoor temperature and humidity. Statistical analysis was used to investigate which factors contribute most significantly to the variability in exposures to large (> 9.8 μm aerodynamic diameter) and small (<3.5 μm) particles. For large particles, the factors of greatest importance in a stepwise analysis of covariance (...

Health effects of gasoline exposure. I. Exposure assessment for U.S. distribution workers.

Personal exposures were estimated for a large cohort of workers in the U.S. domestic system for distributing gasoline by trucks and marine vessels. This assessment included development of a rationale and methodology for extrapolating vapor exposures prior to the availability of measurement data, analysis of existing measurement data to estimate task and job exposures during 1975-1985, and extrapolation of truck and marine job exposures before 1975. A worker's vapor exposure was extrapolated from three sets of factors: the tasks in his or her job associated with vapor sources, the characteristics of vapor sources (equipment and other facilities) at the work site, and the composition of petroleum products producing vapors. Historical data were collected on the tasks in job definitions, on work-site facilities, and on product composition. These data were used in a model to estimate the overall time-weighted-average vapor exposure for jobs based on estimates of task exposures and their duration. Task exposures were highest during tank filling in trucks and marine vessels. Measured average annual, full-shift exposures during 1975-1985 ranged from 9 to 14 ppm of total hydrocarbon vapor for truck drivers and 2 to 35 ppm for marine workers on inland waterways. Extrapolated past average exposures in truck operations were highest for truck drivers before 1965 (range 140-220 ppm). Other jobs in truck operations resulted in much lower exposures. Because there were few changes in marine operations before 1979, exposures were assumed to be the same as those measured during 1975-1985. Well-defined exposure gradients were found across jobs within time periods, which were suitable for epidemiologic analyses.

Magnetic Field Exposures in a Petroleum Refinery

Abstract The purpose of this article is to present extremely low frequency magnetic field exposures to a group of electricians working in a large petroleum refinery. Petroleum refinery workers were classified into groups based on the type of exposure sources and work conducted. Electricians were divided into three categories: high voltage electrical distribution (HVED) workers; low voltage electrical distribution (LVED) workers; and operating unit electrical workers, referred to as maintenance electricians (MNTE). For comparison purposes nonelectrical workers in the refinery and nonoccupational exposures were also determined. The EMDEX-C dosimeter developed by the Electric Power Research Institute was used to determine full-shift magnetic flux density exposure estimates. A total of 48 individuals, 11 HVED electricians, 12 LVED electricians, 11 MNTE workers, and 14 nonelectrical workers were monitored for an 8-hour shift. Both the HVED and LVED groups were found to have average full-shift mean exposures sl...

Carbon Monoxide Exposure in Wildland Firefighting: A Comparison of Monitoring Methods

Abstract The goals of this study were to field test and compare three methods for assessing carbon monoxide (CO) exposures to wildland firefighters, and to acquire additional exposure data to indicate activities and conditions under which this population may be exposed to hazardous CO levels. The three monitoring methods were: 1) passive colorimetric diffusion tubes; 2) electronic datalogging monitors; and 3) end-exhaled air (breath) monitoring. Full-shift time-weighted average CO exposures, determined using passive diffusion monitors, were low for all employees monitored, with a mean of 8.2 ppm (n = 51). These monitors were found to be an easy means for collecting a large number of full-shift CO measurements. The job tasks on these shifts included line construction, backfiring, line holding, and mop-up. Efforts to collect detailed individual activity information by having firefighters make entries in logbooks were largely unsuccessful. Real-time CO exposures for 12 individuals were monitored using electr...

A national cross-sectional study of the working environment in the Danish wood and furniture industry--air pollution and noise.

A cross-sectional survey was carried out in the Danish wood and furniture industry at 200 factories. In this paper, representative estimates of employees' full-shift exposures to wood dust, vapours from organic solvents, formaldehyde and noise dose were calculated using a model for two-stage cluster designs. Exposures to air pollutants were generally below the occupational exposure limits (OELs), while noise doses were at the same level as OEL. The overall exposure to wood dust was 0.90 mg m-3, exposure to vapours from organic solvents was 0.13 C/OEL and noise dose, Leq (8 h), was 90.5 dB(A).

HYDROCARBON EXPOSURES AT PETROLEUM BULK TERMINALS AND AGENCIES

Occupational exposures to the 55 hydrocarbon components of gasoline and petroleum products were measured at the bulk terminals and agencies of six Ontario petroleum companies during the summer of 1986. A total of 82 long-term (full-shift) and 111 short-term personal samples were taken over 3 months. The data, expressed as concentrations in milligrams per cubic meter, were highly variable and appeared to fit the lognormal distribution well. Full-shift exposures of bulk terminal drivers, agency drivers, and plantmen to total hydrocarbons (THC), computed as an n-hexane equivalent, and other hydrocarbon components for which exposure limits exist can be expected to exceed their respective 1986-1987 threshold limit value-time-weighted average (TLV-TWA) no greater than 1% of the time on the basis of the lognormal model. The short-term THC exposures of agency truck drivers can be expected to exceed the 1986-1987 TLV-short-term exposure limits about 7% of the time while top-loading and more than 17% while off-loading. For benzene, the short-term exceedance percentages are 1% and 4% for top- and off-loading operations, respectively. For long-term benzene exposures, up to 69% of the assessments can be expected to exceed the 1990-1991 proposed TLV-TWA of 0.3 mg/m3 (0.1 ppm). The full-shift hydrocarbon exposures of agency drivers were significantly higher than those for bulk terminal drivers. At the bulk terminals, the short-term hydrocarbon exposures during top-loading were significantly higher than during bottom-loading.

Hydrocarbon Exposures at Petroleum Bulk Terminals and Agencies

Occupational exposures to the 55 hydrocarbon components of gasoline and petroleum products were measured at the bulk terminals and agencies of six Ontario petroleum companies during the summer of 1986. A total of 82 long-term (full-shift) and 111 short-term personal samples were taken over 3 months. The data, expressed as concentrations in milligrams per cubic meter, were highly variable and appeared to fit the lognormal distribution well. Full-shift exposures of bulk terminal drivers, agency drivers, and plantmen to total hydrocarbons (THC), computed as an n-hexane equivalent, and other hydrocarbon components for which exposure limits exist can be expected to exceed their respective 1986-1987 threshold limit value-time-weighted average (TLV-TWA) no greater than 1% of the time on the basis of the lognormal model. The short-term THC exposures of agency truck drivers can be expected to exceed the 1986–1987 TLV-short-term exposure limits about 7% of the time while top-loading and more than 17% while off-loading. For benzene, the short-term exceedance percentages are 1% and 4% for top- and off-loading operations, respectively. For long-term benzene exposures, up to 69% of the assessments can be expected to exceed the 1990–1991 proposed TLV-TWA of 0.3 mg/m3 (0.1 ppm). The full-shift hydrocarbon exposures of agency drivers were significantly higher than those for bulk terminal drivers. At the bulk terminals, the short-term hydrocarbon exposures during top-loading were significantly higher than during bottom-loading.