5 Standards Development in the Control of Hazardous Downloaded by UNIV OF MASSACHUSETTS AMHERST on June 4, 2018 | https://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0017.ch005
Contaminants in the Occupational Environment DOUGLAS L . SMITH and JACK E. MCCRACKEN Office of Research and Standards Development, National Institute for Occupational Safety and Health, Washington, D. C. 20852 Although o n e - t h i r d to over o n e - h a l f of our waking hours are spent o n - t h e - j o b , it was not until the t u r n of the century t h a t there was organized concern f o r the worker and h i s working conditions. With the advent of the space program, the p o p u l a t i o n focused its a t t e n t i o n on manned space v e h i c l e s r e q u i r i n g recirculative, r e g e n e r a t i v e , and detoxification procedures f o r prolonged, continuous (24-hour) exposures. P r e v i o u s l y , problems encountered in c l o s e d atmospheres had been of concern almost e x c l u s i v e l y i n submarine o p e r a t i o n s ; thus, the p u b l i c became environmentc o n s c i o u s . Through the F e d e r a l r e g u l a t i o n s contained in the Clean Air A c t (1), p r o v i s i o n s have been made to c o n t r o l air pollution and p r o t e c t the p o p u l a t i o n - a t - l a r g e . I n 1970, a mandate was g i v e n by Congress to assure safe and h e a l t h f u l working c o n d i t i o n s f o r working men and women w i t h the enactment of the Occupational Safety and H e a l t h Act ( 2 ) . Speci fically, the A c t d e c l a r e s t h a t no employee will be exposed to p h y s i c a l agents and substances that will cause impairment of h e a l t h or f u n c t i o n a l c a p a c i t i e s or d i m i n i s h e d life expectancy as a result of h i s work experience. I n a d d i t i o n , the N a t i o n a l Institute f o r O c c u p a t i o n a l Safety and H e a l t h (NIOSH) was estab lished and a u t h o r i z e d by the A c t to conduct research and to p r o v i d e s a f e t y and h e a l t h recommendations to the Department of Labor. One of the most important p r o v i s i o n s of the Occupational Safety and H e a l t h A c t was to a u t h o r i z e NIOSH to develop criteria and recommended standards in the form of criteria documents. These documents s p e c i f y employee h e a l t h hazards f o r specific agents and recommend safe concentrations of a i r b o r n e workplace contaminants w h i l e the employee is o n - t h e - j o b . Additionally, criteria documents i n c l u d e recommendations f o r m e d i c a l s u r v e i l l a n c e which may i n c o r p o r a t e procedures f o r b i o l o g i c m o n i t o r i n g ; l a b e l i n g and p o s t i n g requirements; p r o t e c t i v e e q u i p ment to i n c l u d e skin, eye, and r e s p i r a t o r y p r o t e c t i o n ; educa tional m a t e r i a l to inform employees of h e a l t h hazards; safe work 63
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p r a c t i c e s t o i n c l u d e g e n e r a l h o u s e k e e p i n g and h a n d l i n g , s t o r a g e , and d i s p o s a l r e c o m m e n d a t i o n s ; m o n i t o r i n g and recordkeeping r e q u i r e m e n t s ; and methods f o r e n v i r o n m e n t a l s a m p l i n g and c h e m i c a l analysis. To d a t e , recommended s t a n d a r d s h a v e b e e n d e v e l o p e d f o r 22 c h e m i c a l and p h y s i c a l a g e n t s l i s t e d i n T a b l e I .
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Table I.
NIOSH Recommended S t a n d a r d s D e v e l o p e d Under O c c u p a t i o n a l S a f e t y and H e a l t h A c t
Ammonia Arsenic Asbestos Benzene Beryllium Carbon Monoxide Chloroform Chromic A c i d Coke Oven E m i s s i o n s C o t t o n Dust Hot E n v i r o n m e n t s
the
I n o r g a n i c Lead Inorganic Mercury Noise Silica Sulfuric Acid Sulfur Dioxide Toluene Toluene Diisocyanate Trichloroethylene Ultraviolet Radiation Vinyl Chloride
C e r t a i n aspects of standards development r a i s e s p e c i t i c q u e s t i o n s o f a c h e m i c a l n a t u r e i n e v a l u a t i n g an o c c u p a t i o n a l h e a l t h hazard. For example, the c h e m i c a l p r o p e r t i e s of the n i t r o g e n o x i d e s , p a r t i c u l a r l y n i t r i c o x i d e and n i t r o g e n d i o x i d e , are extremely important from the b i o l o g i c s t a n d p o i n t . The t o x i c i t y o f t h e s e o x i d e s of n i t r o g e n i s g e n e r a l l y a t t r i b u t e d t o n i t r o g e n d i o x i d e , i t s h a v i n g an i r r i t a n t e f f e c t on t h e r e s p i r a t o r y t r a c t p r o d u c i n g cough and sometimes m i l d d y s p n e a w i t h f r e q u e n t r e m i s s i o n o f symptoms f o r up t o 12 h o u r s , f o l l o w e d by p o t e n t i a l l y l e t h a l p u l m o n a r y edema. N i t r i c o x i d e on t h e o t h e r hand has b e e n r e g a r d e d as b e i n g n o n i r r i t a n t , i t s p r i n c i p a l t o x i c i t y s u p p o s e d l y r e s u l t i n g from the c o n v e r s i o n of hemoglobin to methemoglobin w i t h h y p o x i a r e s u l t i n g from methemoglobin production. I n v e s t i g a t i o n s of i n j u r i e s from o c c u p a t i o n a l expos u r e s t o these n i t r o g e n o x i d e s have g e n e r a l l y d i s c o u n t e d the e f f e c t s o f n i t r i c o x i d e ; however, a t h i g h t e m p e r a t u r e s n i t r o g e n combines w i t h oxygen t o produce n i t r i c o x i d e . High concent r a t i o n s of n i t r i c o x i d e i n the w o r k i n g environment have been p r o d u c e d by e l e c t r i c o r gas w e l d i n g o p e r a t i o n s o r e x h a u s t from i n t e r n a l combustion engines. N i t r i c o x i d e may n o t be o x i d i z e d t o n i t r o g e n d i o x i d e as r e a d i l y and c o m p l e t e l y as p r e v i o u s l y b e l i e v e d , i n view of the f a c t t h a t engine exhaust i s r a p i d l y d i l u t e d by a i r , t h u s r e d u c i n g t h e c o n c e n t r a t i o n o f n i t r i c oxide. A t 10,000 ppm, 50% o f n i t r i c o x i d e has b e e n c a l c u l a t e d t o be o x i d i z e d t o n i t r o g e n d i o x i d e i n 24 s e c o n d s w h e r e a s a t 10 ppm, 7 h o u r s w o u l d be r e q u i r e d t o o x i d i z e t h e same p e r c e n t a g e ( 3 ) . R e c e n t l y , n i t r o g e n d i o x i d e has b e e n r e p o r t e d t o p r o d u c e methemoglobinemia i n animals, thus c o m p l i c a t i n g the n i t r i c o x i d e n i t r o g e n d i o x i d e p i c t u r e (4). Furthermore, n i t r o g e n d i o x i d e
Deitz; Removal of Trace Contaminants from the Air ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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5.
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A N D MCCRACKEN
Contaminants
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d i s s o l v e s i n water t o form n i t r i c a c i d , n i t r o u s a c i d , o r n i t r i c o x i d e depending upon t h e t e m p e r a t u r e . Because o f the m o i s t c o n d i t i o n s p r e s e n t i n t h e l u n g s , i t becomes e x t r e m e l y c o m p l i c a t e d f r o m a p h y s i o l o g i c a l s t a n d p o i n t a s t o w h e t h e r t o x i c i t y i s due t o n i t r i c o x i d e , n i t r o g e n d i o x i d e , n i t r i c a c i d , o r n i t r o u s a c i d and a better understanding of thechemical k i n e t i c s involved i s greatly desired. N i t r o u s a c i d h a s b e e n shown t o h a v e p o t e n t e f f e c t s o n t o b a c c o m o s a i c v i r u s and _E c o l i . B i o l o g i c m o n i t o r i n g o f u r i n e o r blood i s u s e f u l as a diagnostic p r a c t i c e t o i n d i c a t e unacceptable absorption of m a t e r i a l s , t h u s p o s i n g a p o s s i b l e r i s k o f i n t o x i c a t i o n . I t must be a s c e r t a i n e d , h o w e v e r , t h a t t h e a n a l y t i c a l p r o d u c t s a r e d u e t o occupational exposures o f t h e environmental contaminant i n q u e s t i o n and n o t d u e t o v a r i a t i o n s o f m e t a b o l i c c o n s t i t u e n t s r e s u l t i n g from normal d i e t a r y i n t a k e . F o r example, e l e v a t e d u r i n a r y h i p p u r i c a c i d l e v e l s may r e s u l t f r o m e i t h e r o c c u p a t i o n a l exposure t o toluene o r from t h e i n g e s t i o n of foods c o n t a i n i n g b e n z o i c a c i d o r benzoates. Other v a l u a b l e b i o l o g i c i n d i c a t o r s i n the u r i n e i n c l u d e p h e n o l as a measure o f benzene e x p o s u r e , u r i n a r y a r s e n i c f o r i n o r g a n i c a r s e n i c e x p o s u r e , and b o t h u r i n a r y l e a d and d e l t a - a m i n o l e v u l i n i c a c i d (ALA) f o r l e a d e x p o s u r e . I n a d d i t i o n t o u r i n a r y déterminât-jcms f o r p o s s i b l e l e a d e x p o s u r e , b l o o d l e a d e v a l u a t i o n s h a v e i n v o l v e d measurements o f d e l t a - a m i n o l e v u l i n i c a c i d d e h y d r a t a s e (ALAD) a c t i v i t i e s a n d b l o o d l e a d d e t e r m i n a t i o n s b y t h e d i t h i z o n e method h a v e b e e n u s e d f o r many years. The m a n u a l d i t h i z o n e method i s c l a i m e d t o b e r e l i a b l e b u t requires experienced, meticulous technicians, extremely clean e q u i p m e n t , and c o n s i d e r a b l e t i m e . The u s e o f p e r s o n a l p r o t e c t i v e e q u i p m e n t , p a r t i c u l a r y r e s p i r a t o r y p r o t e c t i v e devices, i s another important f a c t o r i n t h e s t a n d a r d s s e t t i n g p r o c e s s . The c o n t r o l o f e x p o s u r e s o f w o r k e r s to a i r b o r n e contaminants can best be achieved through i n c o r p o r a t i o n of proper engineering c o n t r o l s , e s p e c i a l l y through t h e u s e o f l o c a l a n d g e n e r a l e x h a u s t v e n t i l a t i o n ; h o w e v e r , some s i t u a t i o n s occur that include s p e c i a l a c t i v i t i e s or nonroutine o p e r a t i o n s f o r w h i c h r e s p i r a t o r y p r o t e c t i o n i s n e c e s s a r y . The use o f r e s p i r a t o r s i n a s p e c i f i c hazardous environment i s l i m i t e d more f r e q u e n t l y b y f a c e p i e c e t y p e a n d f i t t h a n b y t h e a i r p u r i f i c a t i o n d e v i c e t h a t i s e m p l o y e d . D u s t , fume, m i s t , v a p o r , o r g a s f i l t e r s may h a v e c o l l e c t i o n e f f i c i e n c i e s as h i g h a s 15 t o 20,000 ppm b u t q u a r t e r - and h a l f - m a s k f a c e p i e c e f i t g e n e r a l l y l i m i t s r e s p i r a t o r u s a g e t o 10 t i m e s t h e e s t a b l i s h e d e n v i r o n m e n t a l s t a n d a r d and f u l l f a c e p i e c e s a r e l i m i t e d t o 100 t i m e s t h e s t a n d a r d . F o r e x a m p l e , t h e NIOSH recommended e x p o s u r e s t a n d a r d f o r b e n z e n e i s 10 ppm a s a t i m e - w e i g h t e d a v e r a g e ; t h e r e f o r e , h a l f - m a s k usage would be l i m i t e d t o benzene c o n c e n t r a t i o n s a t o r b e l o w 100 ppm a n d f u l l f a c e p i e c e masks t o 1,000 ppm. A n o t h e r f a c t o r t o c o n s i d e r i s t h a t no a i r p u r i f y i n g r e s p i r a t o r s h o u l d b e recommended f o r u s e i n a t m o s p h e r e s w h i c h a r e j u d g e d t o b e hazardous t o l i f e . Such a c o n s i d e r a t i o n i s b a s e d o n b o t h t h e
Deitz; Removal of Trace Contaminants from the Air ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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t o x i c i t y and e x p l o s i v e p r o p e r t i e s o f t h e m a t e r i a l i n q u e s t i o n . The c o n t a m i n a n t may be t o x i c t o t h e employee o r t h e e n v i r o n m e n t a l c o n c e n t r a t i o n may e x c e e d t h e m a t e r i a l ' s l o w e r e x p l o s i v e l i m i t . I n such s i t u a t i o n s the use of a i r - l i n e r e s p i r a t o r s or s e l f - c o n t a i n e d b r e a t h i n g a p p a r a t u s i s recommended. C o n s i d e r a b l e p r o g r e s s has b e e n made i n r e c e n t y e a r s i n t h e u s e o f a c t i v a t e d c a r b o n f o r t h e c o l l e c t i o n o f o r g a n i c v a p o r s and g a s e s . M e t a l l i c coatings s u c h as manganese o r c o p p e r h a v e b e e n employed f o r t h e s u c c e s s f u l s o r p t i o n o f g a s e s s u c h as c h l o r i n e , h y d r o g e n s u l f i d e , and hydrogen cyanide. I n a d d i t i o n , i o d i n e impregnated a c t i v a t e d carbon i s s u p e r i o r to nonimpregnated carbon f o r the i s o l a t i o n of mercury vapor. No e n v i r o n m e n t a l e x p o s u r e s t a n d a r d i s m e a n i n g f u l u n l e s s p r o c e d u r e s a r e a v a i l a b l e t o c o l l e c t and m e a s u r e t h e c o n t a m i n a n t a t c o n c e n t r a t i o n s w h i c h encompass t h e p r e s c r i b e d s t a n d a r d . M e a s u r e m e n t s a t recommended e x p o s u r e l e v e l s f r e q u e n t l y s t r e t c h t h e c a p a b i l i t y o f t h e b e s t a n a l y t i c a l method a v a i l a b l e . In a d d i t i o n , r e s u l t s f r o m an a n a l y t i c a l method a r e no b e t t e r t h a n t h e means by w h i c h t h e s a m p l e s w e r e o b t a i n e d . An a n a l y t i c a l method h a v i n g 2 t o 5 p e r c e n t e r r o r , when combined w i t h a s a m p l i n g e r r o r o f 10 t o 15 p e r c e n t , i s c o n s i d e r e d e x c e l l e n t i n t h e i n d u s t r i a l s i t u a t i o n w h e r e s e l e c t i v i t y o f s a m p l i n g and s p e c i f i c i t y o f a n a l y s i s are d e s i r e d but o f t e n d i f f i c u l t to o b t a i n . The s e p a r a t i o n o f s u l f u r d i o x i d e gas f r o m s u l f u r i c a c i d m i s t c a n be achieved r a t h e r w e l l u s i n g a sampling t r a i n c o n s i s t i n g of a s u i t a b l e p o r e - s i z e f i l t e r f o r p a r t i c u l a t e c o l l e c t i o n f o l l o w e d by gas c o l l e c t i o n i n l i q u i d , p o s s i b l y hydrogen peroxide s o l u t i o n . A n a l y s i s c a n be p e r f o r m e d by a s u l f a t e t i t r a t i o n method; h o w e v e r , d i f f i c u l t i e s o c c u r i n c e r t a i n i n d u s t r i e s s u c h as s m e l t e r o p e r a t i o n s , w h e r e many s o l u b l e p a r t i c u l a t e s u l f a t e s i n t e r f e r e . Also, i t has b e e n f o u n d t h a t e r r o n e o u s s u l f u r i c a c i d d e t e r m i n a t i o n s h a v e r e s u l t e d and h a v e b e e n a t t r i b u t e d t o t h e b i n d e r s u s e d i n most g l a s s f i b e r f i l t e r s . The b i n d e r s h a v e r e a c t e d w i t h t h e s u l f u r i c a c i d b e i n g c o l l e c t e d on t h e f i l t e r . S a m p l i n g p r o b l e m s c o n t r i b u t e m a r k e d l y t o s a m p l i n g e r r o r and a c o n s t a n t e f f o r t must be e x e r t e d t o k e e p t h e e r r o r t o a minimum. As much as 22 p e r c e n t v a r i a t i o n has b e e n o b s e r v e d f r o m p e r s o n a l samples taken s i m u l t a n e o u s l y o n l y 8 i n c h e s a p a r t . Liquid bubblers are f r e q u e n t l y necessary f o r sampling but are not e a s i l y w o r n by w o r k e r s , o f t e n h i n d e r i n g f r e e movement. B a t t e r y powered s a m p l i n g pumps u n t i l r e c e n t l y w e r e i n c a p a b l e o f o p e r a t i n g a t s e t f l o w r a t e s over complete work s h i f t s . B r i e f l y t h e n , the development of o c c u p a t i o n a l e n v i r o n m e n t a l h e a l t h s t a n d a r d s f o r the c o n t r o l of hazardous contaminants r e q u i r e s a c r i t i c a l review of e x i s t i n g i n f o r m a t i o n i n c o n j u n c t i o n w i t h p r o f e s s i o n a l e v a l u a t i o n of i t s s i g n i f i c a n c e to the working situation. I n a d d i t i o n t o c o n s i d e r i n g a c u t e and c h r o n i c h e a l t h e f f e c t s , r e l a t e d problems i n v o l v e m e d i c a l s u r v e i l l a n c e , e n g i n e e r i n g c o n t r o l s , and s a m p l i n g and a n a l y t i c a l p r o c e d u r e s . A m e a n i n g f u l e v a l u a t i o n o f t h e w o r k i n g e n v i r o n m e n t c a n be a c h i e v e d
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only w i t h the c o l l e c t i o n of samples t h a t are r e p r e s e n t a t i v e of the w o r k e r s environment and w i t h a p p r o p r i a t e a n a l y t i c a l chemical methods. 1
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ABSTRACT Under the p r o v i s i o n s of the Occupational Safety and H e a l t h Act of 1970, NIOSH is charged to develop criteria and recommended standards f o r t o x i c m a t e r i a l s to p r o t e c t the h e a l t h of workers. The standards i n c l u d e workplace environmental exposure limits, sampling and analytical procedures, m e d i c a l surveillance, l a b e l i n g and p o s t i n g requirements, p e r s o n a l p r o t e c t i v e equipment and p r o t e c t i v e c l o t h i n g , informing of employees of the h a z a r d s , work p r a c t i c e s , and m o n i t o r i n g and recordkeeping procedures. In support of the e v a l u a t i o n of the hazardous e f f e c t s of a substance, methods f o r sampling and a n a l y s i s are an integral p a r t of standards development, yet problems are presented in the working situation. Low environmental c o n c e n t r a t i o n s , p h y s i c a l occurrence and chemical characteristics of the contaminant, and limitations of equipment capability and l a b o r a t o r y reproducibility are but a few of the f a c t o r s which have i n f l u e n c e d measurements and have limited the availability of meaningful o c c u p a t i o n a l exposure-effect r e l a t i o n s h i p s in the standard s e t t i n g p r o c e s s . A d d i t i o n a l l y , under c e r t a i n circumstances, m o n i t o r i n g the c o n c e n t r a t i o n s of absorbed substances or t h e i r m e t a b o l i t e s ( b i o l o g i c monitoring) provides a v a l u a b l e measurement technique to verify exposure of the individual worker. Levels determined p r i m a r i l y in u r i n e or blood samples may represent unacceptable a b s o r p t i o n of environmental contaminants posing a risk of intoxication.
Literature
Cited
1. Clean Air A c t of 1963, P u b l i c Law 88-206 (42 U . S . C . 1857 et seq.). 2. O c c u p a t i o n a l Safety and H e a l t h A c t of 1970, P u b l i c Law 91-596 (29 U . S . C . 651 et s e q . ) . 3. A u s t i n , A . T.: The chemistry of the higher oxides of n i t r o g e n as r e l a t e d to the manufacture, storage and a d m i n i s t r a t i o n of n i t r o u s o x i d e . B r . J. Anaesth. (1967) 39, 345-50. 4. Greenbaum, R., Bay, J., Hargreaves, M. D., K a i n , M. L., Kelman, G. R., Nunn, J. F., P r y s - R o b e r t s , C., S i e b o l d , K.: E f f e c t s of higher oxides of n i t r o g e n on the anaesthetized dog. B r . J. Anaesth. (1967) 39, 393-404.
Deitz; Removal of Trace Contaminants from the Air ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
