Mean Time-weighted Average Research Articles

Evaluating the impact of occupational noise exposure on workplace fatal and nonfatal injuries in the U.S. (2006–2020)

ObjectivesThis study assessed the relationship between occupational noise exposure and the incidence of workplace fatal injury (FI) and nonfatal injury (NFI) in the United States from 2006 to 2020. It also examined whether distinct occupational and industrial clusters based on noise exposure characteristics demonstrated varying risks for FI and NFI. MethodsAn ecological study design was utilized, employing data from the U.S. Bureau of Labor Statistics for FI and NFI and demographic data, the U.S. Census Bureau for occupation/industry classification code lists, and the U.S./Canada Occupational Noise Job Exposure Matrix for noise measurements. We examined four noise metrics as predictors of FI and NFI rates: mean Time-Weighted Average (TWA), maximum TWA, standard deviation of TWA, and percentage of work shifts exceeding 85 or 90 dBA for 619 occupation-years and 591 industry-years. K-means clustering was used to identify clusters of noise exposure characteristics. Mixed-effects negative binomial regression examined the relationship between the noise characteristics and FI/NFI rates separately for occupation and industry. ResultsAmong occupations, we found significant associations between increased FI rates and higher mean TWA (IRR: 1.06, 95% CI: 1.01–1.12) and maximum TWA (IRR: 1.10, 95% CI: 1.07–1.14), as well as TWA exceedance (IRR: 1.04, 95% CI: 1.01–1.07). Increased rates of NFI were found to be significantly associated with maximum TWA (IRR: 1.06, 95% CI: 1.04–1.09) and TWA exceedance (IRR: 1.03, 95% CI: 1.01–1.05). In addition, occupations with both higher exposure variability (IRR with FI rate: 1.49, 95% CI: 1.23–1.80; IRR with NFI rate: 1.40, 95% CI: 1.14–1.73) and higher level of sustained exposure (IRR with FI rate: 1.27, 95% CI: 1.12–1.44; IRR with NFI rate: 1.21, 95% CI: 1.05–1.39) were associated with higher rates of FI and NFI compared to occupations with low noise exposure. Among industries, significant associations between increased NFI rates and higher mean TWA (IRR: 1.05, 95% CI: 1.02–1.08) and maximum TWA (IRR: 1.06, 95% CI: 1.04–1.08) were observed. Unlike the occupation-specific analysis, industries with higher exposure variability and higher sustained exposures did not display significantly higher FI/NFI rates compared to industries with low exposure. ConclusionsThe results suggest that occupational noise exposure may be an independent risk factor for workplace FIs/NFIs, particularly for workplaces with highly variable noise exposures. The study highlights the importance of comprehensive occupational noise assessments.

Acute Recreational Noise-Induced Cochlear Synaptic Dysfunction in Humans With Normal Hearing: A Prospective Cohort Study

ObjectivesThe objective of the study was to identify the acute high-intensity recreational noise-induced effects on auditory function, especially the cochlear synaptopathy-related audiological metrics, in humans with normal hearing.MethodsThis prospective cohort study enrolled 32 young adults (14 males and 18 females); the mean age was 24.1 ± 2.4 years (ranging from 20 to 29). All participants with normal hearing (audiometric thresholds ≤25 dB HL at frequencies of 0.25, 0.5, 1, 2, 3, 4, 6, and 8 kHz for both ears) had already decided to participate in the outdoor music festival. Participants were asked to measure the noise exposure dose and complete auditory examinations, including the air-conduction pure-tone audiometry (PTA), distortion product otoacoustic emission (DPOAE), contralateral suppression (CS) on transient evoked otoacoustic emission (TEOAE), auditory brainstem response (ABR) test and Mandarin Hearing in Noise Test (MHINT), at baseline and 1 day and 14 days after music festival noise exposure.ResultsThe mean time of attending the music festival was 7.34 ± 0.63 h (ranging from 6.4 to 9.5), the mean time-weighted average (TWA) of noise exposure dose was 93.2 ± 2.39 dB(A) (ranging from 87.9 to 97.7). At neither 1 day nor 14 days post exposure, there were no statistically significant effects on PTA thresholds, DPOAE amplitudes, CS on TEOAEs, or MHINT signal-to-noise ratios (SNRs) of acute outdoor music festival noise exposure, regardless of sex. While the ABR wave I amplitudes significantly decreased at 1 day after exposure and recovered at 14 days after exposure, the exposed/unexposed ABR wave I amplitude ratio was significantly correlated with MHINT SNR change at 1 day after exposure, although it was not correlated with the noise exposure dose.ConclusionIn young adults with normal hearing, we found the self-compared decrement of ABR wave I amplitudes at 1 day post acute recreational noise exposure at high intensity, which also contributes to the change in speech perceptual ability in noisy backgrounds. This study indicated that auditory electrophysiological metric changes might be a more sensitive and efficient indicator of noise-induced cochlear synaptic dysfunction in humans. More attention should be paid to the recreational noise-induced cochlear synaptopathy and auditory perceptual disorder.

Inhalation health risk assessment of occupational exposure to cypermethrin in farmers

ABSTRACT Exposure to cypermethrin is common and can lead to acute and chronic health effects. This study aimed to determine the quantitative inhalation risk ofcypermethrinamong the farmers. This cross-sectional study was conducted in nine areas of Shiraz, Iran. Sampling of the respiratory zone was performed by OSHA PV-2063 method using XAD-2 adsorbent andquestionnaire was used to collect the required demographic characteristics and occupational information. Finally, the inhalation risk assessment for exposure to cypermethrin was performed by the Environmental Protection Agency (EPA) method.The mean time-weighted average (TWA) and hazard quotients (HQ) ranged from 0.21 ± 0.1 to 1.68 ± 0.65 and 0.58 ± 0.11 to 1.68 ± 0.46, respectively. 55.6% and 15.2% of the tree spraying and field spraying of the exposed group had HQ more than 1, respectively. Investigation shows that there is no significant relationship between demographic characteristics and HQ values (except height). Exposure frequency (EF), TWA and exposure hour per day had the strongest relationship with HQ.This study showed that the kind of spraying is effective in the amount of risk exposure. The most focus to reduce the health effects associated with inhalation exposure to cypermethrin should be on lowering TWA and exposure hour per day.Due to the high risk of exposure in farmers, it is necessary to identify other effective factors by conducting further studies and presenting their related practical plans.

Assessment of respiratory exposure to cypermethrin among farmers and farm workers of Shiraz, Iran.

Cypermethrin, a member of the synthetic pyrethroids group, is a popular insecticide used to eliminate a broad range of common bugs in agricultural lands and households. However, studies of farmers' exposure to this insecticide are limited. The present study aimed to measure the respiratory exposure to cypermethrin among farmers and farm workers of Shiraz, as one of the biggest cities in Fars province, Iran. Totally, nine target regions were selected, where 42 individual samples were taken using XAD-2 sorbents and were analyzed by gas chromatography-electron capture detector (GC-ECD). This is the first study on farmers' exposure to insecticides during spraying in Iran. The average concentration of cypermethrin vapor in farmers' respiratory area during spraying was 0.982 ± 0.421mg/m3, which was lower than the permitted threshold value for cypermethrin recommended by the Occupational Safety and Health Administration (OSHA). The mean time-weighted average (TWA) was also evaluated in two distinct occupational groups (tree operators and field operators). The exposure was significantly higher in tree operators than in field operators. A direct correlation was also found between the height of the workers and the amount of cypermethrin (Spearman's r = 0.555). Findings support that farm workers' respiratory exposure to cypermethrin was within the permissible range, but this situation cannot guarantee workers' safety. Total respiratory exposure and skin exposure studies are recommended in future research.

Platinum Mine Workers' Exposure to Dust Particles Emitted at Mine Waste Rock Crusher Plants in Limpopo, South Africa.

The South African mining industry is one of the largest producers of platinum (Pt) in the world. Workers in this industry are exposed to significant amounts of dust, and this dust consists of particles sizes that can penetrate deep inside the respiratory region. A cross-sectional study was conducted to evaluate dust exposure risk at two Pt mine waste rock crusher plants (Facility A and B) in Limpopo, South Africa. Workers’ demographic and occupational information was collected through a structured questionnaire, a walk-through observation on facilities’ processes, and static dust sampling for the collection of inhalable and respirable dust particles using the National Institute for Occupational Safety and Health (NIOH) 7602 and the Methods for Determination of Hazardous Substance (MDHS) 14/4 as guidelines. Only 79% of Pt mine workers, used their respiratory protective equipment (RPE), sixty-five percent were exposed to work shifts exceeding the recommended eight hours and 8.8% had been employed for more than ten years. The mean time-weighted average (TWA) dust concentrations between Facility A and B showed a significant difference (p < 0.026). The Pt mine’s inhalable concentrations (range 0.03–2.2 mg/m3) were higher than the respirable concentrations (range 0.02–0.7 mg/m3), however were all below the respective international and local occupational exposure limits (OELs). The Pt mine’s respirable crystalline silica (SiO2) quartz levels were all found below the detectable limit (<0.01 mg/m3). The Pt miners had increased health risks due to accumulated low levels of dust exposure and lack of usage of RPE. It is recommended that an improved dust control program be put in place which includes, but is not limited to, stockpile enclosures, tire stops with water sprays, and education on the importance of RPE usage.

Comparative Assessment of Formaldehyde Concentrations in Public and Private Mortuaries in Rivers State, Nigeria

Introduction: Formaldehyde is an industrial chemical that is classified as a volatile organic compound (VOC). It is commonly use in mortuaries for the preservation (embalmment) of the dead in Rivers State. Mortuary workers are occupationally exposed to formaldehyde by inhalation and skin contact. This objective/aim of the study was to measure and compare the concentration of formaldehyde in public and private mortuaries of Rivers State, Nigeria.&#x0D; Methodology: This cross-sectional (field) survey was carried out in 9 public and 6 private mortuaries in Rivers State. The Time-Weighted Average (TWA) and short- Term Exposure Limit (STEL) of formaldehyde concentrations in the embalmment sections of the mortuaries were measured using a suitable formaldehyde gas detector instrument. The mortuaries were selected by a multistage sampling technique. Data were collected, entered and analyzed using XL STATA and SPSS and presented in tables and graphs.&#x0D; Results: The mean TWA concentration of formaldehyde in public and private mortuaries was 2.42+-1.77 and 2.52+-0.99 ppm respectively. Also, the STEL concentration measured in public and private mortuaries were 0.91+-0.99 and 1.93+-1.22 ppm. The 8 hour TWA values exceeded OSHA (0.75) and NIOSH (0.016 ppm) standards.&#x0D; Conclusion: There was a high concentration of formaldehyde in both public and private mortuaries which may pose high risk to the health of the mortuary workers of Rivers State. The study recommended health education and surveillance among mortuary workers and good engineering design in the mortuary.

Peripheral tissue oxygenation and the number of organs transplanted per donor.

Current donor management practices target macrohaemodynamic parameters, but it is unclear if this leads to improvements in microvascular perfusion and tissue oxygenation; the latter may have more impact on organ status. In a recent preclinical study we determined that brain death impaired tissue perfusion and oxygen utilisation in swine while pharmacologic correction of these deficits improved organ function and reduced markers of tissue injury. As a first step in translating the preclinical findings, we conducted a prospective observational study to determine if there was an association between peripheral tissue oxygenation (measured by near-infrared spectroscopy) in deceased by neurological criteria human donors and the number of organs transplanted. In 60 donors, the mean time-weighted average of tissue oxygenation was 87.5% (standard deviation, SD, 5.2%) and the average number of organs transplanted was 3.5 (SD 2); there was a positive linear relationship between these two parameters. A 5% rise in tissue oxygenation was associated with an increase of 0.47 organs transplanted (95% confidence intervals 0.16 to 0.78) after adjusting for age (<i>P</i>=0.004). No such correlations were observed for the macrohaemodynamic or macro-oxygenation parameters (including arterial blood oxygenation). The results of this clinical trial are consistent with our preclinical work and support the postulate that targeting the microvasculature to improve tissue perfusion and tissue oxygen delivery in human donors has the potential to increase the quantity of organs suitable for transplant.

At-ear noise levels under the helmet: a field study on noise exposure of young motorcyclists

At-ear noise exposure assessments of motorcyclists, with the function of speed, would be unsafe as on-road data acquisition has certain constraints including the operations and portability of appropriate instrument. Currently, there are no standardized protocols and methods for measuring the noise under motorcycle helmets. Furthermore, standard permissible noise emission levels for commuter motorcyclists are also not defined. Therefore, this study was aimed to investigate the motorcycle noise exposure assessments in realistic environment among young riders. A personal dosimeter was utilized to calculate the daily noise exposure level (L Aeq , 8h) under three different standards including: OSHA-HC (Occupational Safety and Health Administration, Hearing Conservation), OSHA-PEL (Permissible Emission Level) and ACGIH/NIOSH (American Conference of Governmental Industrial Hygienists/ National Institute of Occupational Safety and Health). The study design consisted of noise assessment of riders (age range:19 to 25 years) at-ear under the open-face helmet in-realistic situation (main road to the motorway) motorcycling in dry weather conditions. Personal dosimeter results ( n =52) revealed the average noise exposure level of 93.64 dBA, 92.51 dBA, 95.29 dBA for OSHA-HC, OSHA-PEL and ACGIH/NIOSH respectively. The mean Time-Weighted Average (TWA) was 76.82 dBA, 75.69 dBA, 85.16 dBA for OSHAHC, OSHA-PEL and ACGIH/NIOSH respectively. Under the ACGIH and NIOSH standard, the TWA for motorcyclists is at hazardous limits, which requires further investigations associated with health effects on riders. Standardized methods and configurations should be set for assessing noise exposure related to the motorcycling. Keywords: Motorcycle noise, Wind noise, Dosimeter, OSHA, ACGIH

Toluene Diisocyanate Exposure: Exposure Assessment and Development of Cross-Facility Similar Exposure Groups Among Toluene Diisocyanate Production Plants.

The objective of this study was to characterize workplace toluene diisocyanate (TDI) exposures using standardized industrial hygiene exposure assessment procedures for use in a prospective epidemiologic study of occupational asthma. Over 2300 representative routine full shift time-weighted average (TWA) and short-term high potential exposure tasks (HPETs) air samples in groups across three TDI plants were collected over a nearly 7-year period. Data-derived similar exposure groups (SuperSEGs) were developed across the plants based on TWA sampling using cluster analysis. Individual cumulative exposure estimates were developed on the basis of the SuperSEGs. Workplace TWA exposures to TDI were adequately characterized quantitatively, but HPET exposures were adequately characterized only by qualitative measures. The mean TWA exposure was 0.65 parts per billion for 1594 routine samples. These TWA and HPET exposures can be used to support exposure-response analyses.

Low serum vitamin D levels are not associated with increased postoperative pain and opioid requirements: a historical cohort study.

Vitamin D deficiency has been associated with chronic non-specific musculoskeletal pain syndromes; however, studies are lacking with respect to its relationship with postoperative pain. We tested the hypothesis that a lower preoperative vitamin D level is associated with increased postoperative pain and/or opioid consumption in morbidly obese patients who had laparoscopic bariatric surgery. Data from 185 patients who underwent laparoscopic bariatric surgery at the Cleveland Clinic from 2005-2009 and had a vitamin D level checked within three months of their surgery were included in the analysis. We assessed the relationship between vitamin D levels and the time-weighted average (TWA) of pain scores and total opioid consumption using multivariable regression models adjusted for potential confounders. As a secondary analysis, we compared the TWA of pain scores and opioid consumption between patients who were vitamin D deficient (≤ 20 ng·mL(-1)) and those who were not (vitamin D > 20 ng·mL(-1)). The mean (SD) TWA pain score was 3.8 (1.5) and the median interquartile range [IQR] total opioid consumption (morphine equivalent) was 15.6 [18.2] mg during the first 72 hr postoperatively. The median [IQR] vitamin D concentration was 21.8 [17.1] ng·mL(-1). The vitamin D level was not significantly associated with either the TWA pain score (Pearson correlation: -0.003; 97.5% confidence interval [CI]: -0.17 to 0.16) or opioid consumption (Spearman correlation: -0.13; 97.5% CI: -0.30 to 0.03). After adjusting for confounders, the estimated average change in TWA pain score was 0.01 (97.5% CI: -0.08 to 0.11) for a five-unit increase in vitamin D (P=0.77). The estimated ratio of geometric means of total opioid consumption was 0.94 (97.5% CI: 0.86 to 1.03) for a five-unit increase in vitamin D concentration (P=0.12). No difference was found between patients with vitamin D concentrations > 20 ng·mL(-1) and ≤ 20 ng·mL(-1) in either TWA pain score (P=0.91) or total opioid consumption (P=0.18). We did not find any association between preoperative vitamin D levels and postoperative pain scores/opioid consumption in morbidly obese patients undergoing bariatric surgery.

Concentration of Volatile Organic Chemicals in Small Businesses Located in a Low- Income Latino Community

Background: Although preventable, occupational disease is one of the leading causes of death in the United States, with a disproportionate burden faced by minorities. Small businesses pose a particular risk. They are more likely to employ low-wage minority workers, and often use solvents containing volatile organic chemicals (VOCs) that can cause asthma, cancer, cardiovascular, and neurological disease. These businesses are often minority owned and lack access to culturally and linguistically appropriate occupational health and pollution prevention information due to economic, physical and social factors. Aims: Our objective was to characterize workers’ exposure to VOCs in high-risk small businesses. The study was completed in the marginalized, predominately Latino, area of southern Tucson and focused on these business sectors: 1) auto repair and maintenance, 2) hair and nail salons, 3) print, and 4) woodworking shops. Businesses were recruited via promotoras. A photo-ionization detector, calibrated with isobutylene, was used to measure real-time VOC concentration for approximately 1 hour in 15 businesses. Results: The mean time-weighted average was 15, 5.8, 9.0 and 16 ppm for the auto-repair and maintenance, hair and nail salons, print, and woodworking shops, respectively. However, there was much variability within each sector and there was no significant difference between the sectors. The woodworking sector had the lowest (1.9 x 10-1 ppm) and the highest (3.3 x 101 ppm) mean concentrations, as well as the highest peak concentration (9.9 x 102 ppm). Peak exposures were associated with specific tasks at each business. The concentrations reported in this study are higher than those reported in previously published studies. Conclusions: The results of this study indicate that larger studies are warranted to better characterize the highly variable exposures of this at-risk population and identify tasks associated with peak exposures for intervention development.

Using SPMDs to Assess Natural Recovery of PCB-contaminated Sediments in Lake Hartwell, SC: I. A Field Test of New In-Situ Deployment Methods

Results from the field testing of some innovative sampling methods developed to evaluate risk management strategies for polychlorinated biphenyl (PCB) contaminated sediments are presented. Semipermeable membrane devices (SPMDs) were combined with novel deployment methods to quantify the availability of PCBs at the Sangamo-Weston Lake Hartwell Superfund Site in SC. Three locations in Lake Hartwell were examined: a background site (BKG) with little detectable contamination and two contaminated sites (T-M/N and T-O). PCB availability was quantified using sediment surface samplers designed to hold SPMDs in contact with surface sediments, benthic dome samplers designed to enclose and suspend SPMDs at the sediment-water interface, and commercially obtained SPMD cages suspended in the water column. A two-way analysis of variance showed significant effects by sampler type (P < 0.0001) and site (P < 0.0001) for mean time-weighted average (TWA) total PCBs (t-PCBs). Regardless of the SPMD sampler used, mean TWA t-PCBs were directly proportional to the level of contamination present (BKG < T-M/N < T-O). Water column and surface sediment sampler t-PCB uptake patterns were described by a significant linear fit of the data (r2 = 0.9625, p < 0.0001, and r2 = 0.8188, p < 0.0001, respectively). Dome and sediment surface SPMD samples had a higher percentage of higher chlorinated PCBs compared to water column samples.

Exposure Assessment and Modeling of Quartz in Swedish Iron Foundries for a Nested Case-Control Study on Lung Cancer

Exposure assessment of quartz in Swedish iron foundries was performed based on historical and current measurement data. To evaluate the exposure-response relationship between quartz exposure and lung cancer, we modeled quartz exposure from our database of measurements using determinants job title, time period, and company. Based on these modeled exposure data, we conducted a nested case-control evaluation. In our database, the overall individual, daily time-weighted average (TWA) quartz concentrations of current and historical data varied between 0.0018 and 4.9 mg/m3, averaging 0.083 mg/m3. Job titles with mean TWAs for the whole study period exceeding the European Union recommended occupational exposure limit of 0.05 mg/m3 were fettlers (0.087 mg/m3), furnace and ladle repair (0.42 mg/m3), and maintenance (0.054 mg/m3) workers. The mixed model analysis demonstrated significant determinants on the job level for furnace and ladle repair (β = 4.06; 95% confidence interval [CI] 2.78–5.93). For all jobs, significantly higher exposure levels occurred only during the first time period, 1968–1979 (β = 2.08; 95% CI 1.75–2.47), and a decreasing but not significant trend was noted for the three following 10-year time periods up to 2006 (β = 1.0, 0.96 and 1, respectively). Two iron foundries had significantly higher quartz concentration levels than the others (β = 1.31; 95% CI 1.00–1.71 and β = 1.63; 95% CI 1.00–2.65, respectively). The individual cumulative quartz exposure measures were categorized in low, medium, and high exposure (0.5–<1, 1–1.9 and ≥ 2 mg/m3 *years, respectively). In the nested case-control analysis, we found the highest odds ratios of lung cancer (OR 1.17; 95% CI 0.53–2.55) for the medium exposure group. No dose-response trend or significantly increased risk was determined for our high exposed group (≥2 mg/m3), representing 40 years of exposure at >0.05 mg/m3 of quartz. To conclude, certain foundry workers are still exposed to high levels of quartz, but an increased risk of lung cancer caused by quartz exposure in these Swedish iron foundries could not be confirmed at our exposure levels.

P77 Children's exposure to airborne fine particulate matter at home and asthma outcomes

ObjectivesThe relationship between indoor air exposure to fine particulate (PM2.5) and asthma symptoms in children is uncertain. The aim of the present study was to relate PM2.5 exposure to indices...

Hexavalent Chromium Exposures During Full-Aircraft Corrosion Control

Aluminum alloys used in the construction of modern aircraft are subject to corrosion. The principal means of controlling this corrosion in the U.S. Air Force are organic coatings. The organic coating system consists of a chromate conversion coat, epoxy resin primer, and polyurethane enamel topcoat. Hexavalent chromium (CrVI) is present in the conversion coat in the form of chromic acid and in the primer in the form of strontium chromate. CrVI inhalation exposures can occur when workers spray conversion coat onto bare metal and apply primer to the treated metal surface. In addition, mechanical abrasion of aircraft surfaces can generate particulates that contain chromates from previously applied primers and conversion coats. This study measured CrVI exposures during these corrosion control procedures. Mean time-weighted average (TWA) exposure to chromic acid during conversion coat treatment was 0.48 µg/m3, below the current American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV®) TWA of 50 µg/m3 for water-soluble CrVI compounds. Mean TWA exposures to strontium chromate were 5.33 µg/m3 during mechanical abrasion and 83.8 µg/m3 during primer application. These levels are in excess of the current ACGIH TLV-TWA of 0.5 µg/m3 for strontium chromate. In the absence of a change from chromated to nonchromated conversion coats and primers, additional control measures are needed to reduce these exposures.

Visual and ocular changes associated with exposure to two tertiary amines

Aims: To determine if exposure to dimethylisopropanolamine (DMIPA) and dimethylaminoethanol (DMAE) in a label printing plant was associated with visual disturbances and/or ocular changes. Methods: Questionnaires, eye examinations (visual acuity,...

Hexavalent chromium exposures during full-aircraft corrosion control.

Aluminum alloys used in the construction of modern aircraft are subject to corrosion. The principal means of controlling this corrosion in the U.S. Air Force are organic coatings. The organic coating system consists of a chromate conversion coat, epoxy resin primer, and polyurethane enamel topcoat. Hexavalent chromium (CrVI) is present in the conversion coat in the form of chromic acid and in the primer in the form of strontium chromate. CrVI inhalation exposures can occur when workers spray conversion coat onto bare metal and apply primer to the treated metal surface. In addition, mechanical abrasion of aircraft surfaces can generate particulates that contain chromates from previously applied primers and conversion coats. This study measured CrVI exposures during these corrosion control procedures. Mean time-weighted average (TWA) exposure to chromic acid during conversion coat treatment was 0.48 microg/m(3), below the current American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV(R)) TWA of 50 microg/m(3) for water-soluble CrVI compounds. Mean TWA exposures to strontium chromate were 5.33 microg/m(3) during mechanical abrasion and 83.8 microg/m(3) during primer application. These levels are in excess of the current ACGIH TLV-TWA of 0.5 microg/m(3) for strontium chromate. In the absence of a change from chromated to nonchromated conversion coats and primers, additional control measures are needed to reduce these exposures.

Correlation of year-to-year magnetic field exposure metrics among children in a leukemia survival study.

The Childhood Leukemia Survival Study is examining the possible association between magnetic field exposure and survival of children with newly diagnosed acute lymphocytic leukemia (ALL). We report the results of serial 24-h personal magnetic field monitoring for 412 US and Canadian children and present the correlations between annual values. The mean time-weighted average (TWA) and geometric mean (GM) were similar for first, second, and third year measurements [TWA: 0.11 microT (n = 412), 0.13 microT (n = 304), and 0.12 microT (n = 134), respectively]. There were no consistent differences in mean TWA or GM based on age or gender. Significantly lower mean TWA and GM were found for children living in rural areas. Higher exposures were noted among children living in urban areas, among apartments dwellers, and those living in rental homes. Measurements taken during summer months and among children residing in the northeast and Canada also tended to be higher. Correlations for most metrics were increased among children who had annual measurements performed during the same season. The metric with the highest year-to-year correlation was the GM. The lowest correlations were found for metrics estimating field intermittency and temporal stability. First to second year GMs were well correlated when taken in the same home (Spearman rank correlation = 0.70), but a lower correlation (0.44) was noted among residentially mobile children. Our findings suggest that summarizing exposure using a single measurement of GM can estimate exposures for residentially stable children, but is not a good predictor of personal exposures among children who change residence during the study interval.

Evaluation of occupational exposure to toxic metals released in the process of aluminum welding.

The objective of this study was to evaluate occupational exposure to welding fumes and its elements on aluminum welders in Polish industry. The study included 52 MIG/Al fume samples and 18 TIG/Al samples in 3 plants. Air samples were collected in the breathing zone of welders (total and respirable dust). Dust concentration was determined gravimetrically, and the elements in the collected dust were determined by AAS. Mean time-weighted average (TWA) concentrations of the welding dusts/fumes and their components in the breathing zone obtained for different welding processes were, in mg/m3: MIG/Al fumes mean 6.0 (0.8-17.8), Al 2.1 (0.1-7.7), Mg 0.2 (< 0.1-0.9), Mn 0.014 (0.002-0.049), Cu 0.011 (0.002-0.092), Zn 0.016 (0.002-0.14), Pb 0.009 (0.005-0.025), Cr 0.003 (0.002-0.007), and TIG/Al fumes 0.7 (0.3-1.4), Al 0.17 (0.07-0.50). A correlation has been found between the concentration of the main components and the fume/dust concentrations in MIG/Al and TIG/Al fumes. Mean percentages of the individual components in MIG/Al fumes/dusts were Al: 30 (9-56) percent; Mg: 3 (1-5.6) percent; Mn: 0.2 (0.1-0.3) percent; Cu: 0.2 (< 0.1-1.8) percent; Zn: 0.2 (< 0.1-0.8) percent; Pb: 0.2 (< 0.1-1) percent; Cr: < 0.1 percent. The proportion of the respirable fraction in the fumes and their constituents varied between 10 percent and 100 percent. The results showed that MIG/Al fumes concentration was 1.2 times higher than the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV), and the index of the combined exposure to the determined agents was 2.3 (0.4-8.0), mostly because of high Al2O3 contribution. The background concentrations of the components (ca. 5-10 times lower than those in the breathing zone of the welders) did not exceed the Polish MAC value. The elemental composition of total and respirable fume/dust may differ considerably depending on welding methods, the nature of welding-related operations, and work environment conditions.

Urinary determination of N-acetyl- S-( N-methylcarbamoyl)cysteine and N-methylformamide in workers exposed to N, N-dimethylformamide.

We conducted this biomonitoring study with the aim of evaluating the correlation between the excretion of N-methylformamide (NMF) (mainly from N-hydroxy- N-methylformamide) and N-acetyl- S-( N-methylcarbamoyl)cysteine (AMCC), and levels of exposure to N, N-dimethylformamide (DMF) among occupationally exposed subjects. Exposure levels were determined by personal sampling: breathing zone air samples were collected by means of passive samplers. DMF collected by the charcoal in personal samplers was analysed after extraction with methanol by a gas chromatograph. For the purpose of biological monitoring the levels of NMF and AMCC were measured in pre-shift and post-shift samples. Determinations were carried out by, respectively, gas chromatography and high performance liquid chromatography (HPLC). The mean time-weighted average (TWA) exposure was approximately half (13.5 mg/m(3)) of the current threshold limit value, the range of the values was from 0.4 to 75.2 mg/m(3). Environmental DMF concentrations exhibited a significant correlation with the specific mercapturic acid (AMCC) collected at the end of the working week (AMCC Friday morning mg/l=1.384xDMF (mg/m(3))+8.708; r(2)=0.47; P<0.008]; hence urinary AMCC represents an index of the average exposure during several preceding working days, making it possible to calculate the approximate relationship between DMF uptake and excretion of this metabolite. A significant correlation was found also between the daily excretion of NMF and the corresponding levels of DMF in air. The equation of the regression line was: NMF (mg/g creatinine)=0.936xDMF (mg/m(3))+7.306; r(2)=0.522 ( P<0.0001).