April 16, 1996

Donald J. Garvey, CIH, CSP
Senior Construction Industrial Hygienist
St. Paul Fire and Marine Insurance Company
385 Washington Street
St. Paul, MN 55102-1396

Dear Mr. Garvey:

We have received and reviewed your letter dated March 12. Under the criteria outlined in your letter, both the exposure assessment and the selection of respirators would be acceptable.

OSHA expects that if the periodic monitoring required by 29 CFR 1926.62 indicates an increase in lead exposure, then the level of respiratory protection would be upgraded.

OSHA's Interim Final Rule for Lead in Construction also requires that, if any of the work conditions were to be changed or altered such as increased exposure time, working in a closed work environment, or using shortened acetylene cutting torches, then the level of respiratory protection would be increased to positive pressure supplied air for the interim period until another exposure assessment is completed. With any of these types of changes, once a new exposure assessment has been conducted, the respiratory protection can be adjusted accordingly.

Should you have any questions or if we can be of any further assistance, please contact the Office of Health Compliance Assistance at 202 219-8036.

Sincerely,



John B. Miles, Jr., Director
Directorate of Compliance Programs




March 12, 1996

Ms. Ruth McCully
OSHA Health Compliance Assistance
200 Constitution Avenue, NW.
Washington, DC 20210

Dear Ms.: McCully,

Some of our contractors routinely demolish bridges which requires torch cutting of lead-coated surfaces. Under the Lead in Construction Standard, 29 CFR 1926.62, until the contractor conducts an employee exposure assessment, the contractor must assume the airborne exposure exceeds 2500 ug/M⁽³⁾, and the torch cutters should wear full-face, positive pressure air supplied respirators. Occasionally this work must be done at heights. In some situations the contractors have felt that wearing an air line respirator under these conditions can increase the risk of a fall. Also, many times the cutting jobs are of limited duration, 1 to 2 hours per day, for 510 days. The contractors would prefer to avoid the extra logistics, training, and expense of setting up an air line system for such a limited operation.

Below is an actual scenario from one bridge site. The questions are:

• Is this an acceptable employee exposure assessment under the stated conditions?
• Is this selection of respirators acceptable under the stated conditions?

The project is to remove truss diaphragms from a bridge. The worker will make a total of 10 cuts per day with a maximum duration of 12 minutes per cut. This is approximately 2 total hours of cutting per day. Long handle torches will be used as an engineering control, the work will be done outdoors - no enclosure - so there will be natural ventilation.

Section 29 CFR 1926.62 states that contractors should assume torch cutting airborne lead concentrations exceed 2500 micrograms per cubic meter (ug/M⁽³⁾). Air monitoring by the St. Paul over the last 3 years at bridge renovation projects and reports published by the Steel Structures Painting Council (SSPC Publication 95-05) indicate this level is rarely reached. Typical results have been around 500 to 600 ug/M⁽³⁾. For this discussion however, we will err on the conservative side and assume the worker exposure is twice the OSHA assumption and use 5000 ug/M⁽³⁾.

At 5000 ug/M⁽³⁾, assuming only 2 hours of cutting per day and assuming no other lead exposure to the worker in the remaining 6 hours, the worker's time weighted average (TWA) exposure would be:

(For Figure, click here)

If the worker wears a tight fitting powered air purifying respirator (PAPR) with HEPA filters, the allowable maximum concentration is 2500 ug/M⁽³⁾ according to Table 1. Therefore, even if the original exposure estimate of 5000 was off by a factor of two (exposure was actually 10,000 ug/M⁽³⁾), the PAPR should still provide adequate protection.

The above discussion assumes one person does all the cutting.

Would OSHA consider this an acceptable exposure assessment and a correct selection of respirator?

If you have any questions regarding this please call me at 612 310-7785. I look forward to hearing from you.

Sincerely,



Donald J. Garvey, CIH, CSP
Senior Construction Industrial Hygienist
St. Paul Fire and Marine Insurance Company