1 Sampling and Analytical Methodology for Workplace Chemical Hazards State of the Art and Future Trends
Downloaded by 80.82.78.170 on December 16, 2016 | http://pubs.acs.org Publication Date: April 2, 1981 | doi: 10.1021/bk-1981-0149.ch001
C. CLARINE ANDERSON, ELLEN C. GUNDERSON, and DALE M. COULSON SRI International, Menlo Park, CA 94025 Industrial hygiene sampling and analysis is a rapidly expanding activity in government and industry. Exposures of individuals to toxic substances in workplace environments requires accurate sampling and measurement of gases, liquids and solids. Acceptable methods are now available for at least 400 substances as a result of the NIOSH Standards Completion Program. Miniature impingers and bubblers have been long used for workplace sampling. They are inconvenient to use. Solid sorbent tubes are easier to use and are finding wide applicability. The conversion to solid sorption media from liquid absorption solutions for collection of gases and vapors is a continuing process. The solid sorbent sampling tube is a small device, easily manipulated, and not prone to lose its contents when being used under awkward sampling conditions or during shipping. These physical factors can improve the accuracy of the final result. Filter collection media have become available in a wide variety of materials including glass fibers and many synthetic plastic films. This allows for selection of a filter that is compatible with the analytical method in addition to not altering the physical and chemical characteristics of the particles collected. The field of aerosol technology has grown significantly and with the increased knowledge of particle characterization methodology the effects of specific ranges of particulate matter can be analyzed. Analytical techniques have gone through considerable changes in the past 20 years. With the development of more sensitive and selective analytical instrumentation the analyst has been able to detect and identify minute quantities of materials never before seen. This has brought about a keen awareness of the widespread distribution of toxic hazards and also the need to study the long term effects of low level exposures. The development of new methodology is a dynamic process. However, new methods should always be thoroughly tested to demonstrate the precision and accuracy of the results obtained. SRI International and Arthur D. Little, Inc. carried out an extensive development and validation study between 1974 and 1979 0097-6156/81/0149-0003$05.00/0 © 1981 American Chemical Society
Choudhary; Chemical Hazards in the Workplace ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
C H E M I C A L HAZARDS IN T H E
4
WORKPLACE
for NIOSH i n which approximately 400 methods were s t u d i e d . (.1,2) The study was c a r r i e d out i n two phases. I n the f i r s t phase the major emphasis was on l a b o r a t o r y v a l i d a t i o n of e x i s t i n g methods. In the second phase more emphasis was placed on methods development and the substances that were s t u d i e d were s e l e c t e d from those f o r which v a l i d a t i o n methods were not a v a i l a b l e from the f i r s t phase. The r e s u l t s of these s t u d i e s were presented as i n d i v i d u a l r e p o r t s for each substance. They are a sampling and a n a l y t i c a l method (SAM), a sampling data sheet (SDS), and a backup data r e p o r t (BUD). The r e p o r t s on methods have been p u b l i s h e d by NIOSH and are a v a i l able through the U.S. Government P r i n t i n g O f f i c e , Washington, D.C
Downloaded by 80.82.78.170 on December 16, 2016 | http://pubs.acs.org Publication Date: April 2, 1981 | doi: 10.1021/bk-1981-0149.ch001
P r o t o c o l f o r Methods V a l i d a t i o n A d e t a i l e d p r o t o c o l f o r l a b o r a t o r y v a l i d a t i o n of sampling and a n a l y t i c a l methods f o r t o x i c substances i n workplace environments i s given i n F i g u r e 1. The l i t e r a t u r e was searched and a method of sampling and a n a l y s i s was s e l e c t e d . The next step was to evaluate and, i f necessary, develop an a n a l y t i c a l method t h a t was compatible w i t h the sampling medium. I f a s a t i s f a c t o r y a n a l y t i c a l method became a v a i l a b l e only then d i d we undertake generation of a t e s t atmosphere. Then samples were c o l l e c t e d w i t h the a p p r o p r i a t e c o l l e c t i o n medium. Both c a p a c i t y and c o l l e c t i o n e f f i c i e n c y were evaluated. For each method 18 samples were c o l l e c t e d and a n a l y z e d — 6 samp l e s a t each of the 1/2, 1, and 2 times the OSHA Standard l e v e l . I f the r e s u l t s to t h i s p o i n t i n d i c a t e d a s u c c e s s f u l method, then storage s t a b i l i t y was evaluated. I f a l l requirements of the p r o t o c o l were met, the method was considered l a b o r a t o r y - v a l i d a t e d and a p p r o p r i a t e r e p o r t s were prepared. At v a r i o u s stages of the p r o t o c o l , we evaluated the p r o b a b i l i t y of success w i t h i n the budget f o r each method. I f a t any time i t became apparent t h a t the method study could not be s u c c e s s f u l l y completed w i t h i n budget, l a b o r a t o r y work was d i s c o n t i n u e d and a f a i l u r e r e p o r t was prepared. The b a s i c c r i t e r i o n f o r s u c c e s s f u l v a l i d a t i o n was t h a t a method should come w i t h i n 25% of the " t r u e v a l u e " a t the 95% c o n f i dence l e v e l . To meet t h i s c r i t e r i o n , the p r o t o c o l f o r experimental t e s t i n g and method v a l i d a t i o n was e s t a b l i s h e d w i t h a f i r m s t a t i s t i c a l b a s i s . A s t a t i s t i c a l p r o t o c o l provided methods of data a n a l y s i s that allowed the accuracy c r i t e r i o n to be evaluated w i t h s t a t i s t i c a l parameters estimated from the l a b o r a t o r y t e s t data. I t a l s o gave a means to evaluate p r e c i s i o n and b i a s , independently and i n combination, to determine the accuracy of sampling and a n a l y t i c a l methods. The substances s t u d i e d i n the second phase of the study are summarized i n Table I . S e l e c t i o n of Methods of Sampling and A n a l y s i s A l i t e r a t u r e search was u s u a l l y the f i r s t step that r e s u l t e d i n the s e l e c t i o n o f an a n a l y t i c a l method c o n s i s t e n t w i t h one o f the common sampling methods. The o b j e c t i v e of these methods i s to
Choudhary; Chemical Hazards in the Workplace ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
ANDERSON E T A L .
State of the Art and Future
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