Guidelines for personal exposure monitoring of chemicals: Part V

 

## Fig. a-24. target workplace (test room)
First, a risk assessment supervisor performed basic characterization of the workplace. It was decided that a personal exposure monitoring of toluene should be carried out because toluene was most frequently used. Interviews were conducted with the section manager and engineering staff regarding the organization of the Section, work division, and the contents of work. Observations of the workplace were also conducted.
As a result, a similar exposure group (SEG) was divided into the four groups A to D shown in [fig_ref] Table A - 24: [/fig_ref] SEG-A was mainly involved in physical tests of several chemical products and also half-finished products.
Exposure (eight-hour exposure) was estimated to be "high" for this group because a significant amount of toluene was used in the testing process. SEG-B principally conducted analyses of chemical substances using a gas chromatograph. The exposure to toluene was estimated to be "medium." Toluene was not directly handled in the SEG-C (in charge of the water quality test). However, as the entire room had a l Risk low and frequency low (interval long) [bib_ref] Comprehensive assessment of gasoline exposure of tank truck drivers, Nishikawa [/bib_ref] Initial (previous) control class 2) Risk due to various factors related to exposure risk High Medium Low -APPENDIX -Guidelines for personal exposure monitoring of chemicals: Part V 3 solvent odor, their exposure was still presumed, though estimated to be "low." SEG-D (the administrative staff) was involved in clerical work in a separate room for the majority of the day. Members of this group were limited to entering the workplace on only two or three occasions per day, with a combined time of less than 30 minutes. Their exposure was thus estimated to be "very low"; in fact, far lower than that of SEG-C. Both SEG-A and -B were monitored over a period of two days, collecting five samples from each SEG. To be on the safe side, monitoring was conducted on SEG-C too; in this case a simplified method was used and it took place over just one day. For SEG-C, the number of samples was two. No monitoring was conducted for SEG-D at this time, and it was determined that monitoring would only be performed if exposure of SEG-C turned out to be relatively high. As the result of interviews, it was determined that the contents of the work for each SEG did not change substantially throughout the course of the day and also that there was no work done involving abnormally high short-term exposure. As a result, short-term exposure monitoring was not conducted.
On the day of monitoring, the risk-assessment supervisor briefly explained the purpose of his visit and advised on relevant points in the staff meeting. The section chief selected in advance the workers of each SEG to be monitored among those with routine work scheduled for that particular day. Before starting work, the risk-assessment supervisor attached a passive sampler on the chest of each selected worker and handed a work-recording sheet to them. After observing the working conditions for a short period of time, the risk-assessment supervisor left the workplace. Upon completion of the day's work, the section technical staff (who had been briefed and requested in advance by the risk-assessment supervisor) collected the -APPENDIX -Guidelines for personal exposure monitoring of chemicals: Part V 5 samplers from the workers. They capped (sealed) the samplers, recorded the sampling completion time, and collected all the work-recording sheets. On the following day, and in a similar manner, the remaining monitoring was conducted for SEG-A and -B. Attachment and collection of samplers were again done by the section technical staff.
The risk assessment supervisor submitted the samplers to an external analytical laboratory for analysis.
Finally, after reviewing the contents of the work records, the supervisor verified that there had been no abnormal phenomenon present and also that no irregular work had been performed.
On the basis of the results of this analysis, the risk-assessment supervisor calculated an eight-hour time weighted average exposure. it was proposed to the section chief and the chief's agreement was obtained to change the procedures in the future to house the containers in the fume hood as much as possible, and also, if possible, to perform all work inside the fume hood. It was also communicated to the section chief to report any changes to the risk assessment supervisor.
The risk assessment supervisor submitted a monitoring report to the section chief. In addition, he reported the results of the measurements separately in writing to all the workers monitored. Thereafter, the risk assessment supervisor was invited to attend the section safety meeting. In the meeting, he explained and lectured to the section members regarding the current measurement results and implemented control measures, as well as the SDS for toluene and its toxicity.
For the purposes of reassessment and monitoring, in consideration to the fact that this particular monitoring was the first one in this particular workplace, and also that the risk assessment supervisor did not have a good amount of experience, it was determined that reassessment and monitoring of both SEG-A and -B be carried out after a period of six months. If the results are equal to or better, then it would be considered appropriate for the frequency of reassessment and re-monitoring in the future to be reduced. At the moment, SEG-C is scheduled to undergo reassessment and monitoring after a year. However, if the results of SEG-A and -B after six months are sufficient, the instantaneous measurement shall be conducted for SEG-C instead of the regular monitoring. A Working Environment Measurement agency was requested by a painting Company B to conduct personal exposure monitoring. First, a risk assessment supervisor performed basic characterization of the workplace. The workplace was then divided into a preparation workplace and a painting workplace. [fig_ref] Table A - 24: [/fig_ref] -25.1 shows the work contents and the chemical substances used. In the preparation workplace, three workers were employed in cleaning the surface of the objects to be coated by using a cloth soaked in toluene. They then transported the objects to the painting workplace. In the painting workplace, one worker was employed in mixing the paint with thinner, adjusting its viscosity, and pouring it into a painting machine. This worker would then place the objects on a rotating table in front of the washing booth (which contained external local ventilation equipment). Following the completion of the painting process, the worker would place the objects into the drier for heating and remove them after the completion of drying.
The organic solvents contained in the paint were toluene and xylene, while the thinner itself only contained toluene. In both of these workplaces, ventilation fans were installed on the walls. Working hours ran from 8 a.m. to 5 p.m. with a noon recess of one hour.
In the preparation work, all the toluene in use evaporated into the air. Because local ventilation equipment had not been installed here, it was assumed that exposure was "high" [fig_ref] Table A - 24: [/fig_ref]. In the painting work, a major portion of the toluene and xylene used also evaporated. Although local ventilation equipment had been installed here, because the source of generation was removed a distance away from the hood, exposure was also assumed to be "high" [fig_ref] Table A - 24: [/fig_ref].
Similar exposure groups (SEGs) were formed such that the three preparation workers constituted an SEG-A, and the painting worker, a single individual, constituted an SEG-B. The concentration of toluene exposure was to be monitored for SEG-A, while that of toluene and xylene was to be monitored for SEG-B.
Every member of both SEGs was a target and they were monitored for two days [fig_ref] Table A - 24: [/fig_ref].
On the monitoring day, after arriving at the workplace, the risk assessment supervisor verified the regular work to be performed. This supervisor attached a passive sampler (consisting of activated charcoal)
to the chest of each worker in order to allow the sampling in the breathing zone. They removed the samplers one hour before the end of the work shift and sealed them. During the noon recess the samplers were also removed and closed with a cap due to the fact that they impeded the workers' movements. The sampling duration of the initial monitoring was basically eight hours, but since it took a certain amount of time to travel back and forth between the Working Environment Measurement agency and this particular workplace, the resultant sampling duration was 330 to 347 minutes (excluding the noon recess). Interview with the plant manager and workers indicated that the work during the time periods before and after sampling was the same as that during the sampling time period. The samplers were then transported back to the agency, and, on the following day, after extraction using carbon dioxide, they were analyzed using a gas chromatograph. Xylene also was assessed using the lower (i.e., 50 ppm) of the TLV-TWA (100 ppm) of ACGIH or the permissible concentration (50 ppm) according to the Japan Society for Occupational Health. [fig_ref] Table A - 24: [/fig_ref] shows the results of the assessment. For SEG-A, the AM of toluene was 18 ppm and X 95 was 75 ppm. The results were classified as control class 2B. For SEG-B, when assessed as a mixed exposure, the AM was 2.5 ppm and X 95 was 7.5 ppm (three times the AM because of two measured values). This resulted in its classification as control class 3. As such, it was decided to prepare an improvement proposal, and also to conduct re-monitoring in order to verify the effectiveness of these after improvements. In the mixing work, powdery stearate was handled. This process produced airborne particulates.
Although local exhaust ventilation equipment was installed, it appeared that these particulates did not seem to be adequately removed. Thus, exposure was assumed to be "high" [fig_ref] Table A - 24: [/fig_ref]. In the rolling work, the material mixed by the mixer was kneaded while heated. Initially, this process generated particulates, but with time, and as the viscosity increased, the generation decreased. In this case, exposure was assumed to be "medium" [fig_ref] Table A - 24: [/fig_ref]. In the bagging work, the material was already in a formed pellet type.
Exposure here was assumed to be "low" [fig_ref] Table A - 24: [/fig_ref] were also removed since they disturbed the workers' movements. The sampling time in the initial monitoring was basically eight hours, but since it took a certain amount of time to travel back and forth between the Working Environment Measurement agency and this workplace, the actual sampling time was 350 to 360 minutes (excluding the noon recess). Interview with the plant manager and workers showed that the work during the time periods before and after sampling was the same as that during the sampling time period. The filters were then transported back to the agency, and, on the following day, after the lead was eluted with 2.5 M nitric acid, they were analyzed using an atomic absorption photometer. decided to prepare an improvement proposal and also to conduct re-monitoring in order to verify the effectiveness of these after improvements. Short-term personal exposure monitoring was conducted in the Manufacturing Section of the Plant E of Company D. This Section received ethyl t-butyl ether (ETBE) cargoes every two weeks by ships as an additive to petrochemical products. ETBE is an organic solvent with a boiling point of 73 C and a toxicity similar to that of other general solvents. The following outdoor work was conducted by this section. When a vessel loaded with ETBE arrived at the plant, several workers went onboard and opened the hatch of the hold (an opening and a cover), and then sampled ETBE for quality tests. This is shown in the photograph [fig_ref] Figure A- 27: Sampling work of ETBE [/fig_ref].
First, a risk assessment supervisor performed a basic characterization of the workplace. According to the manager, a certain level of odor emanated during the work. Thus a half-face respirator (with an organic vapor cartridge) was used on a temporary basis while at work. For this reason, it was decided to conduct monitoring without delay. Since workers were exposed to ETBE only during work on this one day, short-term rather than eight-hour monitoring was conducted. Three workers were engaged in the work for approximately 15 minutes or less, and the assumed exposure was "high." [fig_ref] Table A - 24: [/fig_ref] On the day of the monitoring, wind speed was minimal. Thus, the outdoor monitoring was appropriate.
Immediately prior to commencement of the work, a passive sampler was attached to each of the three workers to start sampling. The series of tasks consisted of opening the cover of the hatch (the opening seen surrounded by the three workers in the photograph) and inserting a metallic container (held by the worker on the right side in the photograph) into the hatch. Next, they were to draw it up, pour it into another container, and close the hatch cover. Upon completion of the work, the samplers were removed. The risk assessment supervisor conducted observation during the series of tasks. Thus, a value three times the 25 ppm, that is 75 ppm, was used as a short-term occupational exposure limit.
The Japan Society for Occupational Health has not set the permissible concentration for ETBE.
In this case, the control class turned out to be 2B. Since this work was conducted over a short period of time, its frequency was relatively low, and installation of ventilation equipment onboard was extremely difficult, protective respiratory equipment was required as a risk reduction measure. The protection factor of half-face respirator is 10. Theoretically, this allows for the use of the respirator for a concentration 10 times the reference concentration (occupational exposure limit). Thus the respirator in use was determined to be appropriate. In addition, training was provided on the procedure for the respirator as well as for the periodic maintenance of cartridges. A fit test of the masks (assessment of seal between face and mask) was also conducted. shown in the photograph [fig_ref] Figure A- 28: Loading work of gasoline to a tank truck [/fig_ref].
First, a risk assessment supervisor performed a basic characterization of the workplace. The work included opening the cover of the hatch (the hatch near the worker's feet in the photograph), inserting a gasoline injection pipe (held by the worker in the photograph) into the hatch, and pouring gasoline using a pump. A single injection took about three to four minutes, during which the worker observed the operation while standing at a distance of roughly 1.5 m from the hatch. After the injection, the pipe was pulled out and the hatch was closed. Upon removal of the injection pipe, the pipe was wet with gasoline liquid. As drawing it up, a bucket-type cover was placed on the lower part of the pipe. This was in order to prevent scattering of the liquid. Since one tank truck was loaded with two to six gasoline tanks, the series of work would be completed by repeating this procedure for the number of tanks. The total work time required for the task was 15 to 30 minutes. The worker commented that the odor was detected during the work. Because the work was carried out from the windward side as much as possible, the exposure was estimated to be "medium."
This work is carried out daily, and its scale is very large. Since the total number of workers involved throughout Company E is 2,000, ensuring their safety is considered all-important. Thus, a large-scale monitoring plan was prepared [fig_ref] Table A - 24: [/fig_ref]. Since the protocols remained constant regardless of the workers or the workplace, all the drivers of tank trucks were grouped into one SEG (consisting of about 2,000 workers). For six workers in Plant F, short-term exposure monitoring of the work was conducted on a given day. In order to examine seasonal variance, this monitoring was conducted every two months for one
year, six times in total. Similar monitoring was also carried out in Plant G. As a result, the planned number of samples came to 72. It was planned to conduct monitoring on a day with wind speeds of 5 m/s or less and no rain.
Gasoline and benzene were selected as the substances to be monitored. Gasoline contains about 0.5% benzene, as well as 1% to 10% of toluene, n-hexane, ethyl benzene, and xylene. A past survey had revealed that the health risk of these substances was insignificant when compared to that of gasoline and benzene.
This was in consideration of the relationship between the airborne concentrations of these substances and the occupational exposure limits. Thus, no monitoring was performed for these chemicals. The tank trucks were used for loading and unloading of gasoline in the oil refinery for two to three cycles a day. Thus the drivers were subjected to gasoline exposure throughout the day. Eight-hour exposure monitoring had previously been conducted separately for drivers. The result was in an adequately safe zone.
Concerning the gasoline-to-truck loading work, it was difficult to identify the specific 15-minute period with the highest exposure during the work. For this reason, it was determined that monitoring was to be conducted throughout the work hours. Immediately before the commencement of the work (before workers got on their tank trucks), the risk assessment supervisor attached an active sampler (activated charcoal and explosion-proof sampling pump) to each worker in order to conduct sampling at a sampling rate of 200 mL/min. Immediately after the workers left their tank trucks, which indicated the completion of the work, the samplers were removed and the sampling was finished. The actual monitoring duration was 15 to 30 minutes. This was the same duration as the work hours. The risk assessment supervisor conducted observation during the entire work. were collected. Since all of the sampling times were 15 minutes or more, the concentration measured at each time weighted average was used to calculate statistical indices, and the control class was determined.
The resultant control class for both gasoline and benzene was determined to be 1B.
Analysis was conducted on the results in relation to the workplaces and also to the seasons. However, no significant trends were identified. It was considered that the effect of seasons (temperatures) was less likely to be detected since the compositions of gasoline were adjusted depending on them. It was alleged that the workers detected an odor, but the measurement results were lower than expected. It is possibly because the short term occupational exposure limit was considerably high (500 ppm), and the operators were close to the hatch only for a short period of time.
From the above results, it was determined that the current work procedure had no issues or problems.
For further safety, it was made well known to the tank truck drivers that unless absolutely necessary, during the loading work they should seek to position themselves as far back from the hatch as possible.
[fig] Figure A- 23: Conceptual diagram to determine the frequency of reassessment and monitoring Appendix 24: Example of Personal Exposure Monitoring (eight-hour monitoring, test work, organic solvents) [/fig]
[fig] Appendix 25: Example of Personal Exposure Monitoring (eight-hour monitoring, painting work, organic solvents) [/fig]
[fig] Figure A- 27: Sampling work of ETBE (outdoor, onboard) [/fig]
[fig] Figure A- 28: Loading work of gasoline to a tank truck (outdoor) [/fig]
[table] Table A -: 24.1. Classification of SEG and assumption of exposure [/table]
[table] Table A: Note: Occupational exposure limit of toluene is 20 ppm (ACGIH-TLV-TWA) * SEG; Similar Exposure Group: AM; Arithmetic Mean: [/table]