Monitoring Airborne Contaminants in Chemical ... - ACS Publications

12 Monitoring Airborne Contaminants in Chemical Laboratories

Downloaded by NORTH CAROLINA STATE UNIV on January 13, 2013 | http://pubs.acs.org Publication Date: April 22, 1980 | doi: 10.1021/bk-1980-0120.ch012

FRED HERTLEIN III INALAB, 1523 Kalakua Avenue, Suite 101, Honolulu, HI 96826

The Occupational Safety and Health Act (PL 91-596, OSHA) protects workers against safety and health hazardsinthe occupational environment, and requires that all employees be provided a safe and healthy work environment. Can students be defined as "workers" or "employees" according to OSHA? University staff and instructors can be defined as employees, however, a student's protection under OSHA is unclear. Recently, students were provided all the "protection" that employees have under OSHA. A university was questioned by students if they were exposed to toxic gases and vapors during organic chemistry laboratory sessions. University authorities resolved the students' question by conducting a one month program of air monitoring during four summer session laboratory classes. Concentrations of a variety of organic vapors from solvents used in routine laboratory experiments were measured. Samples of air from the student's breathing zone were collected, and the concentrations determined by gas chromatography. These concentrations were compared with current levels allowed f o r safe worker exposure to the vapors. The levels also permitted assessment of the laboratory hoods and exhaust v e n t i l a t i o n system f o r effective removal of air contaminants. EXPERIMENTAL The sampling and a n a l y t i c a l method employed i n determining the various solvent vapor concentrations i n a i r are described i n d e t a i l by White e t a l (1)and NIOSH 92). Four Bendix National Environmental Instruments Model BDX 30 Personal Samplers were used d a i l y (one i n each laboratory) with large size charcoal tubes (SKC cat no. 226-09-100) which contained two sections of activated charcoal per tube (a 400 milligram section f o l l o w e d by a 200 mg backup s e c t i o n t o i n d i c a t e when "breakthrough" o f t h e main s e c t i o n has o c c u r r e d ) * The sampling pumps were operated a t a r a t e o f one l i t e r per minute and were c a l i b r a t e d by means o f an Environmental Compliance C o r p o r a t i o n Model 302 U n i v e r s a l Pump C a l i b r a t o r ( a device t h a t generates a t h i n f i l m of soap which i s c a r e f u l l y timed as i t t r a v e r s e s a v e r y 0-8412-0539-6/80/47-120-215$05.00/0 © 1980 American Chemical Society In Analytical Techniques in Occupational Health Chemistry; Dollberg, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

OCCUPATIONAL


216

HEALTH

CHEMISTRY

determined because h i g h l y p o l a r compounds such as ketones, amines, organic a c i d s , and a l c o h o l s , are o f t e n r e p l a c e d on charc o a l by l e s s p o l a r hydrocarbons. The NIOSH method of d e s o r p t i o n e f f i c i e n c y determination i n v o l v e s d i r e c t i n j e c t i o n o f known q u a n t i t i e s of the s o l v e n t ( s ) onto t h e c h a r c o a l i n the sampling tube* The open ends o f the tube are capped, arid the tube remains a t room temperature f o r one day before a n a l y s i s . During t h i s one day, the s o l v e n t ( s ) r e d i s t r i b u t e themselves between the f r o n t and r e a r s e c t i o n s o f c h a r c o a l . Amount recovered/amount i n j e c t e d i s t e r a e d the d e s o r p t i o n e f f i c i e n c y when expressed as a p e r c e n t age. I n these s t u d i e s CS2 was used as the d e s o r p t i o n s o l v e n t . The d e s o r p t i o n e f f i c i e n c y changes from compound, t o compound, s o l v e n t t o s o l v e n t , and between batches of c h a r c o a l . The a f f i n i t y t h a t the s o l v e n t vapor has f o r the a c t i v a t e d c h a r c o a l o r the c h a r c o a l ' s a d s o r p t i v i t y i s r e f l e c t e d i n the " c o l l e c t i o n e f f i c i e n c y . E a r l y s t u d i e s U * 3) show t h a t f o r many s o l v e n t s , c o l l e c t i o n e f f i c i e n c i e s are s i m i l a r . No g e n e r a l i z a t i o n i s without exception and t h e r e f o r e t e s t atmospheres should be generated where t h i s i n f o r m a t i o n i s important. The c o l l e c t i o n e f f i c i e n c y and d e s o r p t i o n e f f i c i e n c y , together w i t h the a n a l y t i c a l p r e c i s i o n and accuracy are i n c o r p o r a t e d i n t o the t o t a l c o e f f i c i e n t o f v a r i a t i o n f o r the method. Many solvent vapor sampling methods are not t h i s thoroughly documented i n the l i t e r a t u r e because of the d i f f i c u l t y of generating known t e s t atmospheres. I n t h i s study both d i r e c t i n j e c t i o n and f l o w i n g of v a p o r - a i r mixtures over the c h a r c o a l were used f o r e f f i c i e n c y determinations; these v a l u e s are r e p o r t e d i n t a b l e 1 and r e q u i r e d much time and e f f o r t t o o b t a i n . 1 1

RESULTS Sampling f o r v a r i o u s hydrocarbon vapors i n l a b o r a t o r y atmospheres r e q u i r e s c o o r d i n a t i o n and scheduling. Since a l l the chemistry l a b o r a t o r y experiments are known a t the beginning o f the semester, a sampling schedule c o n c e n t r a t i n g on key chemicals can be arranged. Compounds t h a t can be expected t o become a i r b o r n e on each p a r t i c u l a r day can be a n t i c i p a t e d . The h i g h l y v o l a t i l e compounds w i t h h i g h vapor pressure a r e candidates f o r monitoring e i t h e r as product, i n t e r m e d i a t e or r e a c t a n t i n an experiment. L i s t i n g the compounds t h a t can be expected f o r each day o f the semester a i d s i n s c h e d u l i n g . Only compounds l i s t e d by 0SHAv4)as having a time-weighted-average (TWA) t h r e s h o l d l i m i t value (TLV) should be monitored. The pre-survey d e s c r i b e d above h e l p s p l a n sampling, determine the number o f c h a r c o a l tubes needed, and helps p l a n l a b o r a t o r y work f o r d e s o r p t i o n s t u d i e s and sample analyses r e q u i r e d . The pumps r e q u i r e d f o r a study w i l l have t o be c a l i b r a t e d , recharged, and maintained. The pre-survey h e l p s p l a n f o r these a c t i v i t i e s . Sampling v i a l s and s o l v e n t s f o r standards and d e s o r p t i o n can be ordered based on the pre-survey.

In Analytical Techniques in Occupational Health Chemistry; Dollberg, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.


15.

14.

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. II. 12. 13.

Trial No.

Acetone Benzene Bromobenzene Chloroform Diethyl ether Dioxane Ethanol Hexane Methanol Methy1 eye 1ohexa no 1 Methylene c h l o r i d e Petroleum ether Bromobenzene Hexane Ether Ether Methanol Dioxane Chloroform Methylene c h l o r i d e Ether Benzene Hexane Dioxane

Components

TABLE 1 EFFICIENCY STUDIES

76 94 92 103 86 82 105 0 65 88 89 91 100 82 89 0 88 137 100 93 94 1 19 80

69 90 87 98 85 99

107 26 82 97 92 63 100 79 90 0 83 133 86 94 94 107 87

78

96 83

85 86

92 76

1 1 1 0 68 96 103 85 83 107 136 93 0 86 80 103 93 97 100 100

72 94 98 98 71 91

Percent Recovery

93 80

70

Desorption E f f i c i e n c y ( D i r e c t Spikes)

108 9 72 96 89 79 102 99 91 0 86 1 17 96 93 95 109 89

75 91 92 100 87 85

Av Pet

73 102 76 141 143 87 0 81 99 86 83 86 109 72

30

71 106

82 91 81 220 57 93 0 82 99 91 101 97 105 84

18

73 107

25

101 64 84 107 21 107 0 64 80 139 1 10 47 107 193 96 90 1 12 145 64 76

14

57 100

48 87 99 70 85 76

24

Percent Recovery

18

OveralI E f f i c i e n c y (Flowed Spikes)


85 86 80 156 74 96 0 76 93 84 1 17 88 11 1 74

22

67 104

Av Pet


17.

16.

Trial No. 109 97 72 70 105 104 68 78

Av Pet 69 65 55 28

Flow rates through large s i z e tubes ( o v e r a l l

2.

mg. mg.

85 57 63 75

Recovery

Efficiency

79 57 57 54

Av Pet

I LPM f o r four hours.

83 50 51 58

Percent

OveralI

e f f i c i e n c y ) was

Large s i z e ; charcoal s e c t i o n a = 400 charcoal s e c t i o n b = 200

103 1 14 66 75

Charcoal

Tube:

103 100 66 88

Percent Recovery

Desorption E f f i c i e n c y

1.

NOTES

Benzene Ethanol Acetone Methy1 eye 1ohexano1

Components

TABLE 1 (Con't) EFFICIENCY STUDIES


12.

HERTLEiN

Airborne

Contaminants

in

Laboratories

219

a c c u r a t e l y known volume)* Before sampling, the tube i s opened a t each end and c l i p p e d v e r t i c a l l y on the s t u d e n t s c o l l a r near the breathing zone. The tube i s connected t o t h e sampling pump w i t h Tygon t u b i n g and the pump i s attached t o t h e student s b e l t . Sampling d u r a t i o n i s timed u s i n g a w r i s t watch synchronized t o the chemistry department's l a r g e w a l l c l o c k s . The c h a r c o a l tube samples were capped and l a b e l l e d upon completion o f sampling. Sampling data sheets were f i l l e d out l i s t i n g person's name, pump number, f l o w r a t e , i n i t i a l and f i n a l sampling t i m e , and sample number. A d d i t i o n a l i n f o r m a t i o n on compounds t o be analyzed f o r and p o t e n t i a l i n t e r f e r e n c e s a r e listed. Samples are r e t u r n e d t o the l a b o r a t o r y f o r a n a l y s i s along w i t h a f i e l d blank. The c h a r c o a l tube samples were desorbed w i t h 2 ml. o f chromatoquality carbon d i s u l f i d e (CS2)> dispensed w i t h an automatic p i p e t t e , i n v i a l s w i t h T e f l o n - l i n e d septum caps. V i a l s were a g i t a t e d f o r 30 minutes on an SKC developing v i b r a t o r equipped w i t h an automatic t i m e r . Standards and spiked c h a r c o a l tubes w i t h known amounts o f s o l v e n t were prepared w i t h Hamilton s y r i n g e s . A V a r i a n Model 1800 Gas Chromatograph equipped w i t h a flame i o n i z a t i o n d e t e c t o r was used t o analyze the CS2-desorbed samples. Two GC colums were used: 1


1

(1) a Porapak Q, 100/120 mesh, 6' χ 2 mm i . d . s t a i n l e s s s t e e l column, (designated as column A i n Table I I ) , and (2) a 20£ SP-2100 and O.lg Carbowax 1500 on a Supelco-port 100/120 mesh, 20' χ 2 mm i . d . s t a i n l e s s s t e e l column (designated as Column Β on Table I I ) High p u r i t y n i t r o g e n c a r r i e r gas was used as t h e c a r r i e r gas. An A u t o l a b Model 6300 D i g i t a l I n t e g r a t o r was used w i t h t h e V a r i a n GC t o p r o v i d e a d i r e c t readout o f e l u t i o n time (seconds) and r e l a t i v e area under each peak. A Honeywell E l e c t r o n i c 194 r e c o r d e r d i s p l a y e d e l u t i o n times and peak h e i g h t g r a p h i c a l l y . Gas sampling tubes w i t h T e f l o n stoppered v a l v e s on each end and a septum i n the center were used t o generate a i r b o r n e concentrations of various solvents i n a i r f o r " o v e r a l l e f f i c i e n c y " s t u d i e s . ( F i g u r e 1 ) . I n t h i s manner, both t h e degree of a f f i n i t y t h a t the carbon has f o r each vapor and t h e degree o f CS2 d e s o r p t i o n f o r each s o l v e n t can be determined when they a r e t r e a t e d as normal samples. Amount recovered a f t e r CS2 d e s o r p t i o n d i v i d e d by amount v o l a t i l i z e d i s termed the o v e r a l l e f f i c i e n c y when expressed a s a percentage .Generating known c o n c e n t r a t i o n s i n t h i s manner i s u s u a l l y d i f f i c u l t , so an e a s i e r method i s employed which a l l o w s one t o determine o n l y the degree o f CS2 d e s o r p t i o n o r the " d e s o r p t i o n e f f i c i e n c y " , (which has been shown t o g e n e r a l l y be f a i r l y comparable t o t h e " o v e r a l l e f f i c i e n c y " d e f i n e d as the sum o f " c o l l e c t i o n e f f i c i e n c y " and " d e s o r p t i o n efficiency") E i t h e r the " d e s o r p t i o n " o r " o v e r a l l " e f f i c i e n c y must be



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Preparation of Paranitroani1 ine

F-3

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Chemistry Experiment Title

Lab/ Samp le No.

TABLE I I (Continued)

92

95

207

200

d i e t h y l ether hexane acetone bro/Dobenzene benzene

d i e t h y l ether hexane acetone bromobenzene benzene

acetone et ha no 1 benzene

acetone ethano 1 benzene

Total Air Sample Components Sought (Liters)

3.7 3.9 0.2 0.06 0.07

2.9 2.9 0.2 0,024 0.05

0.75 0 0.05

1.5 0 0.05

Total Quantity (mg)

0.74 1 .00 0.57 0.80 0.88

0.74 1 .00 0.57 0.80 0.88

0.57 0.57 0.79

0.57 0.57 0.79

Eff Corr

5.0 3.9 0.35 0.08 0.08

3.9 2.9 0.35 0.03 0.06

17.9 12.0 1 .6 0.14 0.27

13.5 8.7 1 .6 0.05 0.20

2.6 0 0.09

5.5 0 0.09

2.6 0 0.06 1.3 0 0.06

Concen (ppm)

Correc Tot Qty (mg)


0.0052*

0.014*

0.0050

0.0060

Em

165 1 1 1 15 1 .2 2.5

129 82 15 0.47 1.9

55 0 1.9

109 0 1 .9

**Ceil Concen (ppm)

12.

Airborne

HERTLEiN

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Contaminants

in Laboratories

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Lab/ Samp le No.

TABLE I I (Continued)

200

165

145

acetone ethanol petroleura ether benzene

acetone ethanol petroleum ether benzene

benzene raethylene chlorî de acetone ethanol

Total Air Samp le Components Sought (Liters)

0.57 0.57 0.86 0.79

0.04

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* The " c e i l i n g " concentration was not determined in t h i s survey because samples must be taken f o r a sampling period of only 10 minutes. However, " c e i l i n g " c o n c e n t r a t i o n s can be estimated under a "worst" p o s s i b l e instance by assuming t h a t a l l of the m a t e r i a l was c o l l e c t e d during a time i n t e r v a l of 10 minutes. By using the r e l a t i o n s h i p ppm = 24450 χ mg/L MW where ppm expresses our estimated peak value, MW represents the molecular weight of the organic compound, mg represents the t o t a l amount of substance found (4th column from the end) and L i n d i c a t e s the number of l i t e r s of a i r t h a t would have been sampled in a 10 minute i n t e r v a l , we can obtain an estimate as t o t h i s highest p o s s i b l e value. T h i s i s the manner in which the l a s t column was caI eu Iated.

i s a v a i l a b l e to

* Time t h a t student i s actual I y exposed t o C

1

Concentration measured in s t u d e n t s breathing zone f o r same component

8 hours or 480 minutes or time allowed f o r TLV

TLV f o r one component

c

Em = a a + CbTb + C T

The yalue of E

T

c.

Ί

m

E i s the e q u i v a l e n t exposure of an i n d i v i d u a l t o a mixture which i s defined as f o l l o w s :

* Does not r e f l e c t broroobenzene exposure since no TLV determine mixed exposure.

where :

NOTES



230

OCCUPATIONAL

HEALTH

CHEMISTRY

R e s u l t s f o r v a r i o u s l a b o r a t o r y experiments a r e shown i n Table I I . The s a l i e n t f e a t u r e s o f t h i s Table a r e t h e v e r y low vapor c o n c e n t r a t i o n s noted i n t h e t h i r d column from t h e end. These v a l u e s represent about a f o u r hour exposure and should t h e r e f o r e be h a l v e d i n o r d e r t ο o b t a i n the 8 - h o u r time-weighted average c o n c e n t r a t i o n . I n comparing these v a l u e s with OSHA standards, i t must be borne i n mind t h a t OSHA c r i t e r i a r e f l e c t two l e v e l s o f p r o t e c t i o n . F i r s t , t h e eight-hour THA i s a l e v e l below which a worker can s a f e l y f u n c t i o n d u r i n g an eight-hour day, 4 0 hour week. The c e i l i n g v a l u e i s a c o n c e n t r a t i o n which can be t o l e r a t e d f o r no more than f i f t e e n minutes d u r i n g an eight-hour work s h i f t . C e i l i n g c o n c e n t r a t i o n s were not a c t u a l l y measured, but were c a l c u l a t e d on a "worst" p o s s i b l e case b a s i s . I t was assumed t h a t a l l o f t h e organic vapor(s) trapped on t h e c h a r c o a l were obtained d u r i n g a 1 5 min. sampling i n t e r v a l . T h i s h i g h l y u n l i k e l y assumption can be s u c c e s s f u l l y u t i l i z e d when i t i s suspected t h a t t h e 8 - h o u r Ti/A c o n c e n t r a t i o n s w i l l be low. One should a l s o be aware t h a t s k i n a b s o r p t i o n may be as s e r i o u s a problem as i n h a l a t i o n on some o c c a s s i o n s . Some experiments show t r a c e s o f acetone, methylene c h l o r i d e , chloroform, benzene, and dioxane i n t h e a i r . Only i n one i n s t a n c e (chloroform) was a TLV exceeded. However, pump e r r o r may have caused t h i s r e s u l t . When many s o l v e n t s o r a i r con taminants c o e x i s t i n the environment, a t o t a l o r e q u i v a l e n t exposure must be c a l c u l a t e d . The e q u i v a l e n t exposure r e f l e c t s the c o n t r i b u t i o n o f each contaminant t o t h e t o t a l exposure. I n these s t u d i e s t h i s v a l u e was v e r y low and can be noted i n t h e next t o l a s t column o f Table I I . S o l v e n t s l i k e benzene, chloroform, and dioxane a r e p r e s e n t l y suspected carcinogens (j>) and l a b o r a t o r y i n s t r u c t o r s should r e p l a c e these compounds w i t h s a f e s u b s t i t u t e s whenever p o s s i b l e . BIBLIOGRAPHY 1. White, L.D., Taylor, D.G., Mauer, P.Α., and Kupel, R.E., "A Convenient Optimized Method for the Analysis of Selected Solvent Vapors i n the Industrial Atmosphere," Amer. Ind. Hyg. Assoc. J., March - April, 1970, pp. 225-232. 2. "Manual of NIOSH Analytical Methods," 4 volumes, USDHEW, PHS, CDC, National Institute for Occupational Safety and Health, Cincinnati, Ohio, 1974. 3. NIOSH Contract HSM-99-72-98, Scott Research Laboratories, Inc., Collaborative Testing of Activated Charcoal Sampling Tubes for Seven Organic Solvents, 1973. 4. Federal Register, 39, Number 125, June 27, 1974, Occupational Safety and Health Standards. 5. Suspected Carcinogens, A Subfile of the Registry of Toxic Effects of Chemical Substances, HEW Publication no.(NIOSH) 77-149, USDHEW, PHS, CDC, NIOSH, Cincinnati, Ohio, December 1976. RECEIVED December 4, 1979.


Monitoring Airborne Contaminants in Chemical ... - ACS Publications

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