해외산업간호정보 - 미국 산업안전보건연구원(National Institute for Occupational Safety and Health) 소개

Objective
Manganese (Mn), an established neurotoxicant, is a common component of welding fume. The neurological phenotype associated with welding exposures has not been well described. Prior epidemiologic evidence linking occupational welding to parkinsonism is mixed, and remains controversial.

Increased risk of parkinsonism associated with welding exposure

Background: Welders are frequently exposed to Manganese (Mn), which may increase the risk of neurological impairment. Historical exposure estimates for welding-exposed workers are needed for epidemiological studies evaluating the relationship between welding and neurological or other health outcomes. The objective of this study was to develop and validate a multivariate model to estimate quantitative levels of welding fume exposures based on welding particulate mass and Mn concentrations reported in the published literature.

Methods: Articles that described welding particulate and Mn exposures during field welding activities were identified through a comprehensive literature search. Summary measures of exposure and related determinants such as year of sampling, welding process performed, type of ventilation used, degree of enclosure, base metal, and location of sampling filter were extracted from each article. The natural log of the reported arithmetic mean exposure level was used as the dependent variable in model building, while the independent variables included the exposure determinants. Cross-validation was performed to aid in model selection and to evaluate the generalizability of the models.

Results: A total of 33 particulate and 27 Mn means were included in the regression analysis. The final model explained 76% of the variability in the mean exposures and included welding process and degree of enclosure as predictors. There was very little change in the explained variability and root mean squared error between the final model and its cross-validation model indicating the final model is robust given the available data.

Conclusions: This model may be improved with more detailed exposure determinants; however, the relatively large amount of variance explained by the final model along with the positive generalizability results of the cross-validation increases the confidence that the estimates derived from this model can be used for estimating welder exposures in absence of individual measurement data.

/pdf/estimation-of-particulate-mass-and-manganese-exposure-levels-23jipw6gt2.pdf

Estimation of particulate mass and manganese exposure levels among welders.

http://digital.csic.es/bitstream/10261/200215/1/Source%20specific%20exposure%20and%20risk%20assessment%20for%20indoor%20aerosols.pdf

Source specific exposure and risk assessment for indoor aerosols

Welding is a major industrial process used for joining metals. Occupational exposure to welding fumes is a serious occupational health problem all over the world. The degree of risk to welder’s health from fumes depends on composition, concentration, and the length of exposure. The aim of this study was to investigate workers’ welding fume exposure levels in some industries in Jeddah, Saudi Arabia. In each factory, the air in the breathing zone within 0.5 m from welders was sampled during 8-hour shifts. Total particulates, manganese, copper, and molybdenum concentrations of welding fumes were determined. Mean values of eight-hour average particulate concentrations measured during welding at the welders breathing zone were 6.3 mg/m3 (Factory 1), 5.3 mg/m3 (Factory 2), 11.3 mg/m3 (Factory 3), 6.8 mg/m3 (Factory 4), 4.7 mg/m3 (Factory 5), and 3.0 mg/m3 (Factory 6). Mean values of airborne manganese, copper, and molybdenum levels measured during welding were in the range of 0.010 mg/m3–0.477 mg/m3, 0.001 mg/m3–0.080 mg/m3 and 0.001 mg/m3–0.058 mg/m3 respectively. Mean values of calculated equivalent exposure values were: 1.50 (Factory 1), 1.56 (Factory 2), 5.14 (Factory 3), 2.21 (Factory 4), 2.89 (Factory 5), and 1.20 (Factory 6). The welders in factories 1, 2, 3, and 4 were exposed to welding fume concentration above the SASO limit value, which may increase the risk of respiratory health problems.

https://www.mdpi.com/1660-4601/7/7/2978/pdf

Total Fume and Metal Concentrations during Welding in Selected Factories in Jeddah, Saudi Arabia

This study assessed a professional pipefitter/welder performing shielded metal arc welding on carbon steel under field conditions. The resulting breathing zone (near field) and area (far field) welding fume concentration data were applied to the two-zone model for the purpose of determining field-derived personal exposure emission (generation) rates during actual welding work. The study is unique in that one welder was evaluated under high production conditions for 2 days at two different welding locations: a boiler room and a breezeway. Samples were collected and analyzed for total particulate following NIOSH Method 0500 and for select metals following NIOSH Method 7300. Breezeway average personal breathing zone sample total particulate concentrations ranged from 2.89 mg/m(3) to 4.38 mg/m(3), Fe concentrations ranged from 0.53 to 0.63 mg/m(3), and Mn concentrations ranged from 0.10 to 0.12 mg/m(3). The boiler room average personal breathing zone sample total particulate concentrations ranged from 4.73 mg/m(3) to 5.90 mg/m(3), Fe concentrations ranged from 0.48 to 0.85 mg/m(3), and Mn concentrations ranged from 0.06 to 0.16 mg/m(3). Average arc times ranged from 20 to 25% of the total sampling time. Both tracer gas and anemometer techniques were used to estimate ventilation of the boiler room. The steady-state form of the two-zone model was applied to long-term and short-term sample total particulate, Fe, and Mn concentrations obtained during welding in the boiler room and breezeway. The average generation rate in the boiler room was 39.2 mg/min for TP, 6.4 mg/min for Fe, and 1.3 mg/min for Mn. The average generation rate in the breezeway was 40.0 mg/min for TP, 6.6 mg/min for Fe, and 1.2 mg/min for Mn. The field-based generation rates were considerably lower than laboratory-derived published emission rates of between 280 and 650 mg/min for TP. This study emphasizes the need for field-derived welding fume generation rates and showed the personal breathing zone and area sample concentrations can be described by the two-zone model in a way that may help the industrial hygienist estimate exposures. [Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Occupational and Environmental Hygiene for the following free supplemental resource: Tables detailing the personal breathing zone and average area sample results for breezeway welding and boiler room welding, two-zone modeling results, and boiler room welding personal breathing zone and area sample results with mixing fans on.].

Two-Zone Model Application to Breathing Zone and Area Welding Fume Concentration Data

I am writing to comment on the article by Boelter et al., titled “Two-Zone Model Application to Breathing Zone and Area Welding Fume Concentration Data,” JOEH, Volume 6, pp. 298–306, 2009. I commend the authors for presenting a good deal of useful exposure data and for their attempt to apply a modeling analysis to estimate an average fume emission rate during actual welding work. Although I am a proponent of using modeling to estimate exposure intensity,(1) and of the near field/far field (NF/FF) model in particular,(2) the latter model as applied by the authors is not a valid descriptor for the welding scenario. In turn, I believe the authors overestimated the near field dilution ventilation rate. I also believe that the authors underestimated the fume emission rate and inappropriately estimated a “mixing factor” for the boiler room venue. The NF/FF model with a constant contaminant emission rate G (mg/min) assumes that 100% of the emitted mass mixes instantaneously into the NF zone air. However, the authors stated that “visual observation showed that the welding plume rose past the welder’s breathing zone and stratified in the upper portion of the room.”(p.304) Thus, 100% of the emitted fume did not mix instantaneously into the NF zone air. Instead, some fraction f1× G mixed into the NF zone, and the complementary fraction (1 − f1) × G passed directly into the lower room air zone. My experience in monitoring welding operations is that some portion of the plume that enters the lower room air zone also passes directly through it (without mixing into the lower zone air) into the upper room air zone. If f2 is the fraction of (1 − f1) × G that mixes into the lower room zone, the complementary fraction (1 − f2) × (1 − f1) × G passes directly into the upper room zone. This behavior is consistent with the “stratification” of the fume as noted by the authors. Where the room air inlets and outlets are all located in the lower room zone, as appears to have been the case in the authors’ boiler room setting, I believe a three-zone model is more appropriate. Let CNF, CLR, and CUR denote the fume concentration (mg/m3) in, respectively, the NF zone, the lower room zone, and the upper room zone. Let VNF, VLR, and VUR denote the respective zone volumes (m3). Let β (m3/min) denote the airflow rate between the NF and lower room zones, let β2 (m3/min) denote the airflow rate between the lower room and upper room zones, and let Q (m3/min) denote the airflow into and out of the room. The coupled mass balance equations for the fume in the NF, lower and upper zones are, respectively:

Laurel Berman

Papers

Two-Zone Model Application to Breathing Zone and Area Welding Fume Concentration Data

A three-zone model for welding fume concentrations.