May 22, 2001
Mr. Bruno Santucci
Safety Advisor - BC Interior Service Area
Canadian Pacific Railway
Golden, BC
Subject: Air Sampling for Metals During Field Frog Welding and Grinding
Background
On April 9 and 10, 2001, an industrial hygiene assessment was conducted to determine the level of exposure to airborne metals that an employee incurs while welding and grinding frogs. The assessment was commissioned in order to determine the need for any protective measures to prevent employee overexposure to airborne metals. The major concern for welders and welder helpers (Labourers) working with rail frogs is the potential for exposure to manganese (a major component of rail frogs). The following people were present for the sampling:
· John Mott, Welder, Engineering Services - Golden
· Leo Shuist, Labourer, Engineering Services - Golden
· Bruno Santucci, Safety Advisor - BC Interior
· Bob Tully, Industrial Hygiene Specialist, Canadian Pacific Railway
Legislative Requirements and Corporate Guidelines
Worker Health and Safety at Canadian Pacific Railway is legislated by, “Regulations Respecting Occupational Safety and Health made under Part II of the Canada Labour Code”.
Section 10 of the Regulations pertain specifically to Hazardous Substances and Section 10.19 states that:
An employee shall be kept free from exposure to a concentration of an airborne chemical agent, other than grain dust or airborne chrysotile asbestos, in excess of the value for that chemical agent adopted by the American Conference of Governmental Industrial Hygienists, in its publication entitled Threshold Limit Values and Biological Exposure Indices, 1994-1995, as amended from time to time.
Approach to Air Sampling Measurements
All air sampling measurements for airborne metals was conducted in accordance to the National Institute for Occupational Safety and Health (NIOSH) Method 7300, "Elements by ICP". Air samples were collected inside the employees breathing zone, where possible. In Golden the sampling filter cassette was placed inside the welding helmet to best represent his personal exposure.
Once the sampling train was in place, a battery powered air sampling pump was used to draw a known volume of air through a 37-mm matched weight, MCE filter. At the commencement of the sampling period the filter cassette was removed, sealed and sent to an accredited laboratory for analysis.
The sampling train was calibrated before and after the sampling period using a BIOS DryCal calibrator.
Results
The results of each sample are shown in Table 1, along with the appropriate TLV, where applicable. Although there were no airborne metal concentrations that exceeded the corresponding TLV, the airborne concentrations of manganese did exceed our recommended action limit of 100 mg/m3 and showed that there is the potential for overexposure to the employee, in the absence of respiratory protection.
Table 1
Air Sampling Results for Metals (mg/m3)
April 9 and 10, 2001
|
Metal |
Sample 1 Frog Welder Golden |
Sample 2 Labourer Golden |
Sample 3 Welder Tappen |
Sample 4 Area Sample on Truck - Tappen |
ACGIH TLV-TWA mg/m3 |
|
Aluminum |
16.82 |
0.97 |
194.61 |
<1.15 |
5000 |
|
Arsenic |
0.15 |
<0.12 |
<0.24 |
<0.29 |
10 |
|
Barium |
<0.13 |
<0.12 |
<0.24 |
<0.29 |
500 |
|
Beryllium |
<0.13 |
<0.12 |
<0.24 |
<0.29 |
2 |
|
Calcium |
<0.50 |
<0.49 |
<0.97 |
<1.15 |
2000 |
|
Cadmium |
<0.03 |
<0.02 |
<0.05 |
<0.06 |
10 |
|
Cobalt |
<0.13 |
<0.12 |
<0.24 |
<0.29 |
20 |
|
Chromium |
18.83 |
1.21 |
23.18 |
<1.15 |
500 |
|
Copper |
0.78 |
<0.12 |
<0.24 |
<0.29 |
200 |
|
Iron |
296.18 |
28.13 |
540.85 |
4.59 |
5000 |
|
Mercury |
<0.03 |
<0.02 |
<0.05 |
<0.06 |
25 |
|
Potassium |
<12.55 |
<12.13 |
<24.15 |
<28.69 |
2000 |
|
Magnesium |
0.75 |
0.49 |
11.11 |
<1.15 |
10000 |
|
Manganese |
63.00 |
9.23 |
136.18 |
2.98 |
200 |
|
Molybdenum |
<0.50 |
<0.49 |
2.41 |
<1.15 |
10 |
|
Sodium |
<12.55 |
<12.13 |
<24.15 |
<28.69 |
na |
|
Nickel |
4.09 |
0.34 |
10.38 |
0.34 |
1500 |
|
Lead |
<0.50 |
<0.49 |
<0.96 |
<1.15 |
50 |
|
Antimony |
<0.13 |
<0.12 |
<0.24 |
<0.29 |
500 |
|
Selenium |
<0.13 |
<0.12 |
<0.24 |
<0.29 |
200 |
|
Tin |
<1.26 |
<1.21 |
<2.41 |
<2.89 |
na |
|
Strontium |
<0.25 |
<0.24 |
<0.48 |
<0.57 |
na |
|
Vanadium |
<0.25 |
<0.24 |
<0.48 |
<0.57 |
50 |
|
Tungsten |
<1.26 |
<1.21 |
<2.41 |
<2.87 |
5000 |
|
Zinc |
<0.13 |
<0.12 |
0.34 |
0.46 |
5000 |
|
Zirconium |
<0.25 |
<0.24 |
<0.48 |
<0.57 |
5000 |
As shown by Table 1, there were no metals that exceeded the applicable TLV. Significant levels of airborne manganese were detected in the breathing zone samples of each welder. The measured airborne concentration for the welders in Golden and Tappen were 31.5% and 68% of the TLV respectively. These sampling concentrations show that the potential does exist for a worker's exposure to exceed the action level of 100 mg/m3 and the TLV of 200mg/m3.
Discussion
On April 9th (the day Golden samples collected) repair work was being conducted on the frog at switch No.17 in Golden Yard. There was a fairly strong breeze out of the northeast. The airflow was parallel to the track passing from the right side of the welder to the left. It was an overcast day, approximately 0 oC with sporadic precipitation. The welder was wearing a welding helmet (10-11 tint) safety boots and hearing protection. The was no tent/umbrella being used and the welder was not wearing any respiratory protection. The welder set-up a portable fan to discharge welding fume away from the his breathing zone however, the majority of the fumes were quickly removed by the natural breeze on the day of inspection. These sampling conditions would be considered a "best case" situation due to the instant fume dilution and removal resulting from the breeze.
During the first half hour of the sampling period the grinder was being used to prepare the frog for new material. The frog was being built up over a 9-12 inch area. The frog was then built up with "Track Weld 564" wire. The wire-feed unit was malfunctioning periodically which slowed the process down somewhat.
The samples collected on April 10, 2001, in Tappen, BC, were done so under slightly different conditions. There was a slight breeze and it was a clear sunny day. ARTEC wire was used. The first half hour was spent preheating the frog. 7/8 of the time was spent welding and 1/8 of the time was spent grinding. A Vortek fan was used to draw the fumes away from the welder. The welder wore respiratory protection in addition to the basic personal protective equipment (safety boots, coveralls and welding mask).
The sample results have been reported as a time-weighted average for the duration of the sample. The welder's 8-hour time-weighted average personal exposure to airborne metal fumes and particulates would be less on occasions where a portion of the shift is spent on activities that do not generate metal fume and particulate.
Recommendations
Based on the findings of this investigation, field frog welders require respiratory protection during welding, cutting or grinding operations. As a minimum, the appropriate respirator would be a half facepiece air purifying respirator. The appropriate respirators are specified in the CPR Respiratory Protection Program and are also listed below:
· 3M 6000 series half facepiece mask with 3M 2097 P100/OV filter cartridges
· 3M 8514 N95/OV particulate respirator
· North 77BP Series half facepiece backpack respirator with the North 7583 P100/OV filter cartridge
The Selection, Care and Use (including fit-testing) of any respirator must be in accordance with the CPR Respiratory Protection Program.
The practice of using portable fans to draw the fumes/particulates away from the welder's breathing zone is an effective way to reduce the risk of overexposure. As a best practice the welder should take advantage of any prevailing winds when setting up the fan.
Training that details the associated hazards to such agents as manganese should be provided to employees required to weld rail frogs. The training should also include information on best practices to minimize the potential for overexposure.
In addition to the inhalation concerns, ingestion of manganese must be prevented. Certain work practices such as smoking at the frog welding location can greatly increases the amount of manganese ingested during the shift. Employees working with materials such as manganese must be aware that activities such as cigarette smoking, eating and drinking must not be performed in a contaminated area and it is imperative that the proper hygiene precautions are taken.
CPR will be releasing the manganese control guidelines in 2001. Employees that are potentially exposed to the a concentration of 100 mg/m3 for at least 30 days a year are required to participate. The program will include elements such as awareness training and voluntary medical monitoring/tracking.
If you have any further questions, please do not hesitate to contact me at (403) 319-6226.
Sincerely,
Bob Tully
Industrial Hygiene Specialist
Safety and Program Development