June 8, 2021

OSHA Introduces “Sampling Groups” for Analytical Methods

By Ed Rutkowski

June 8, 2021—Three representatives from OSHA’s Salt Lake Technical Center (SLTC) discussed the agency’s efforts to update methods for industrial hygiene sampling and laboratory analysis in a recorded presentation delivered last week as part of Virtual AIHce EXP 2021. According to Phil Smith, director of the Division of Industrial Hygiene Chemistry at SLTC, the updates will benefit both field industrial hygienists and the labs that analyze IH samples by ensuring consistent procedures are used across laboratories for several of OSHA’s most used methods.

As part of its update, OSHA has created several “sampling groups”—aggregates of multiple analytes that can be sampled and analyzed by the same method. To illustrate sampling groups, Smith and Daren Pearce, a chemist with SLTC, explained the development of OSHA Method 5000 (PDF) for organic vapors such as benzene, n-hexane, isobutyl acetate, and others. Method 5000 replaces Method 7 (PDF), which the agency has withdrawn.

As written, Method 7—collection on charcoal, extraction with an organic solvent, and analysis by gas chromatography with a flame ionization detector—can apply to more than 70 substances. Laboratories often had to modify the method to obtain data on the wide variety of analytes submitted by their IH customers, Smith said. These modifications differed across laboratories, complicating attempts to compare results; sometimes, even chemists within the same laboratory would use different procedures under the auspices of Method 7. The method’s instructions were “almost taken as a license to do just about anything,” Smith said. “I think in a lot of instances, people would read the parts of this method that they wanted to read, and maybe [they] ignored other parts.”

“We’ve seen people really stretch this method beyond its limits,” Pearce said. “We’ve seen people use it for passive dosimeters. We’ve seen people use it for thermal desorption tubes. That really wasn’t the intent of OSHA Method 7.

“OSHA wanted to take the guesswork out of this and make it so everyone knows exactly how those samples were run and be able to compare the data across chemists and across laboratories.”

The result is OSHA Method 5000, which corresponds to what the agency calls Organic Vapor Sampling Group 1. According to this method, samples are collected on coconut charcoal sorbent tubes and extracted by carbon disulfide. The method can be used to sample and analyze 19 total analytes, and it replaces 12 old OSHA methods for active air sampling. The old methods have been withdrawn.

The use of Method 5000 allowed SLTC to reduce the number of gas chromatographs it maintains from two dozen to ten, Pearce said. It has also resulted in consistent sample preparation and analysis techniques, and the standardized process allows for easier quality-control checks.

“We don’t have to cite a bunch of internal work instructions or modifications,” Pearce said. “We can actually follow the method as written.”

Other new OSHA methods include Method 5001 for alcohols collected on synthetic charcoal sorbent tubes (PDF) and Method 5002 for diisocyanates collected on coated glass fiber filters (PDF). These methods correspond to OSHA Organic Vapor Sampling Groups 2 and 3, respectively. Together, these two methods update and replace nine old OSHA methods that have since been withdrawn.

Daniel Johansen, the Spectroscopy and Physical Measurements Group Manager at SLTC, joined the presentation to discuss updates to OSHA’s spectroscopic methods. So far, the agency has published OSHA Method 5003 for metals collected on a mixed cellulose ester filter (PDF). The method is used for the analytes in Metals Sampling Group 1, which includes arsenic, cadmium, and lead. The ultimate goal, Johansen said, is to create a “universal metals sampling group.”

To date, Smith said, OSHA’s updates have resulted in the withdrawal of 45 obsolete methods, with more to come. OSHA also plans to revise its validation guidelines for air sampling using chromatographic analysis (PDF) to harmonize with relevant standards from the International Organization for Standardization.

“It’s important that an industrial hygiene chemistry laboratory have valid guidelines,” Smith said. “We recognize that you can’t always [follow a method as written]. But we think it’s important that if you’re going to change something, you do it as rarely as you possibly can, and if you do have to do it, you make sure that you have validation data for your changes.”

Ed Rutkowski is editor in chief of The Synergist.