A Health Hazard Evaluation of Nitrosamines in a Tire Manufacturing

18 A

Health

Hazard

Evaluation

of N i t r o s a m i n e s i n

Downloaded by NORTH CAROLINA STATE UNIV on January 7, 2013 | http://pubs.acs.org Publication Date: April 2, 1981 | doi: 10.1021/bk-1981-0149.ch018

a Tire M a n u f a c t u r i n g P l a n t J. D. McGLOTHLIN, T. C. WILCOX, and J. M. FAJEN National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, OH 45226 G. S. EDWARDS New England Institute for Life Sciences, Waltham, MA 02154 In a preliminary study we have recently reported (1) that the air in three rubber and tire industry plants was contaminated with several N-nitroso compounds. The compounds included N-nitrosomorpholine (NMOR), N-nitrosodimethylaminne (NDMA), and N-nitrosodiphenylamine (NDPhA). The latter compound is used as a vulcanization retarder, so its presence near processes employing it was not surprising. Bismorpholine-carbamylsulfonamide, a cross-linking accelerator used in rubber tires, was found in tire factories and may be contaminated with NMOR. The source of the NDMA was not identified, but it could arise from nitrosation of amines which may be decomposition products of diamine based accelerators, as pointed out by Yeager, et al (2). Our present work, reported here, covers the results of four separate survey visits made to a single tire plant. It strongly suggests that NMOR may be generated by transnitrosation of morpholine by NDPhA when these two chemicals are used together. Although such transnitrosation has been shown to occur experimentally (3,±,5) , this is the first instance we are aware of where this occurrence may result in human exposure to NMOR, a known animal carcinogen (§). The chemical structures of four nitrosamine compounds found in this tire plant and three typical vulcanization accelerators and stabilizers used in the tire industry are in Figure 1. Efforts to improve the worker environment through engineering controls and chemical substitution, and the results of a brief survey of biological samples (blood, urine, and feces) obtained from the workers during two of the NIOSH visits are also reported. Background. The tire plant in Maryland produces bias-ply passenger, truck, and off-road tires 24 hours per day, 7 days per week. On the average, the tire company mixes approximately 0097-6156/81/0149-028 3$05.00/ 0 © 1981 American Chemical Society

In Chemical Hazards in the Workplace; Choudhary, G.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

284

CHEMICAL

NDPhA

NMOR

Ν -Ν = Ο


HAZARDS IN T H E W O R K P L A C E

Ο

Ν- Ν = Ο

Ό/ NDMA

NPYR

Ν - Ν= 0

^

\

- Ν= Ο

CH / 3

CH,

|^V" >1 S

S

S

Ν

Ο CH

4-M0RPH0LIN0

3

2 BENZOTHIAZOLE DISULFIDE

2 ( 2 , 6 - D I M E T H Y L , 4 MORPHOLINETHIO) BENZOTHIAZOLE

CH

CH

S II Ν — C —

3 v

\

3

/ 3

Ο II / S—S—C — Ν X

CH

3 6

CH

3

TETRAMETHYLTHIURAMDISULFIDE Figure 1.

Volatilized N-nitrosamines found in this tire plant and typical vulcaniza tion accelerators and stabilizers used in the tire industry



18.

McGLOTHLIN

ET AL.

Nitrosamines in a Tire Plant

285

6000 batches of rubber per month f o r passenger and o f f - r o a d t i r e s , and another 2000-2,500 batches per month f o r truck t i r e s . Batch weights range between 400-500 pounds each. During the manufacture of truck t i r e tread and b i a s - p l y rubber approximately two pounds of NDPhA, a r e t a r d i n g agent which c o n t r o l s the time of rubber cure, are added to each rubber batch. In August 1979, NIOSH took short term workplace a i r samples (approximately 2 to 3 hours) of truck t i r e rubber batches o n l y . On subsequent NIOSH v i s i t s workplace a i r sampling was longer (approximately 5 to 7 hours), and included passenger t i r e rubber batches (65 to 75 percent of a l l batches sampled) which d i d not c o n t a i n NDPhA. Nitrosamines found during NIOSH surveys were p r i m a r i l y i n "hot process" areas where rubber i s heated by f r i c t i o n and compression from m i l l i n g , extruding, and curing o p e r a t i o n s . The m i l l i n g and calendering temperatures range from 200-230°F, while extruding and curing operations range from 300-350°F. The term "process sampling" used i n t h i s r e p o r t , r e f e r s to workplace a i r samples c o l l e c t e d approximately one foot away from a t i r e manufacturing process. The word "calendering" r e f e r s to the sandwiching of rubber onto nylon f a b r i c to make the p l i e s for b i a s - p l y t i r e s . M a t e r i a l s and Methods A i r Samples. Airborne nitrosamines were c o l l e c t e d with a Thermo-Sorb/N* a i r sampler (2) connected to a battery-operated pump (DuPont, model P-4000)* which had been c a l i b r a t e d using a 500 ml bubble b u r e t t . The pumps were operated between 1.5 and 3.0 L/min. A i r sampling ranged from 1 to 8 hours. The a i r c o l l e c t o r s were t i g h t l y capped and returned to the laboratory for a n a l y s i s of nitrosamines. They were e l u t e d with 2 mL of methanol-dichloromethane (1:3, v / v ) — a n d d i r e c t l y i n j e c t e d i n t o a gas chromatograph (GC) and/or high performance l i q u i d chromatograph (HPLC), each equipped with a TEA Thermal Energy Analyzer; (Thermo E l e c t r o n * , Waltham, MA) d e t e c t o r . The GC-TEA c o n d i t i o n s used f o r the d e t e c t i o n of v o l a t i l e nitrosamines have been described by Fine and Rounbehler (8). A 14' χ 1/8" s t a i n l e s s s t e e l column packed with 5% Carbowax 20M c o n t a i n i n g 2% NaOH on Chromosorb W HP (80-100 mesh) was operated at 175°C with argon gas as the c a r r i e r a t a flow rate of 15 mL/min. A TEA was used as the detector with dry i c e / e t h a n o l as the c o l d t r a p . The HPLC-TEA was constructed by s e q u e n t i a l l y connecting a high pressure pump (Altex, model 110), an i n j e c t o r (Waters, model U6K), a p P o r a s i l column (Waters), and a TEA. The operation of HPLC-TEA has been described by F i n e , e t a l . (9,)·


286

CHEMICAL

HAZARDS IN T H E W O R K P L A C E


The samples were screened using two d i f f e r e n t s o l v e n t systems: 4% acetone and 96% isooctane f o r NMOR q u a n t i t a t i o n , and 0.5% acetone i n isooctane f o r the determination o f NDPhA. B i o l o g i c a l Samples. There were three types o f b i o l o g i c a l samples obtained from workers a t the p l a n t : u r i n e , whole blood, and f e c e s . A l l u r i n e and blood samples were i n t e r n a l l y "spiked" at the f a c t o r y with 1 yg/mL o f a n i t r o s o p i p e r i d i n e (NPiP) standard. NPiP was used f o r s p i k i n g because i t has a s i m i l a r s t a b i l i t y and recovery c h a r a c t e r i s t i c t o nitrosomorpholine, and to provide a means o f gauging the accuracy o f the a n a l y t i c a l methods. Due t o the i n a b i l i t y t o perform homogeneous mixing o n - s i t e , the feces samples were not spiked u n t i l they were thawed upon r e t u r n t o the l a b o r a t o r y . E t h y l acetate e x t r a c t s o f urine samples were examined f o r the presence o f N-nitrosodiethanolamine (NDEIA), a metabolite o f NMOR, by HPLC-TEA. A l l samples were immediately frozen a t the p l a n t (-80°C) and kept a t t h i s temperature u n t i l a n a l y s i s . Urine Samples. A n a l y s i s f o r NMOR: Ten mL o f thawed urine were placed on a Preptube c a r t r i d g e (Thermo E l e c t r o n Corp.) and e l u t e d with 60 mL o f dichloromethane (DCM). The Preptube was pre-wet with DCM before r e c e i v i n g the sample. The r e s u l t i n g s o l u t i o n was concentrated to a volume o f 1 mL a t 55°C using a Kuderna-Danish apparatus. The concentrate was analyzed f o r NMOR by GC-TEA. Recoveries o f the i n t e r n a l standard (NPiP) were t y p i c a l l y 80-100%. A n a l y s i s f o r NDEIA; Ten mL o f the thawed u r i n e were placed on another Preptube, pre-wet with e t h y l a c e t a t e . The sample was washed with 60 a d d i t i o n a l m i l l i l i t e r s o f e t h y l acetate and the e f f l u e n t d r i e d (rotary evaporator) t o 1 milliliter. I t was then analyzed by HPLC-TEA using a U N H 2 column e l u t e d with isooctane:dichloromethane:methanol (60:30:7). Recoveries f o r NDEIA using t h i s method were approximately 70%. The percent recovery was judged by an i n t e r n a l spike o f N-nitrosodipropanolamine. Blood Samples. Ten mL blood samples were analyzed f o r NMOR, using the method described f o r urine samples. Recoveries o f the NPiP standard were more v a r i a b l e , ranging from 32 t o 87%. Feces Samples. Twenty t o 45 grams o f samples were weighed out and ground t o a f i n e powder i n a blender c o n t a i n i n g l i q u i d n i t r o g e n . The r e s u l t i n g homogenate was placed i n a 500 mL d i s t i l l a t i o n f l a s k with 50 m i l l i l i t e r s o f mineral o i l (containing 1 mg/mL of α-tocopherol [to prevent n i t r o s a t i o n during d i s t i l l a t i o n ] ) and allowed t o thaw. The contents o f the


18.

McGLOTHLIN E T AL.

Nitrosamines

in a Tire Plant

287

f l a s k were mixed with 500 ng o f NPiP t o determine the recovery of the method. The feces samples were d i s t i l l e d under a vacuum of 2.2 t o r r a t up t o 130°C f o r 1 hour. Recoveries o f NPiP were low, approximately 20%. Results A i r Samples; NMOR, NDMA, and NPYR were found during the f i r s t NIOSH v i s i t i n a i r samples c o l l e c t e d a t a t i r e manufacturing p l a n t i n Maryland. One process sample, c o l l e c t e d at a f e e d m i l l , contained 250 yg/M o f NMOR, a l e v e l s e v e r a l times higher than has been reported f o r any airborne nitrosamine at any i n d u s t r i a l s i t e (1). Maximum concentrations o f NDMA and NPYR found i n the hot process areas were 4.4 yg/M and 3.4 pg/M , r e s p e c t i v e l y . Over the f o l l o w i n g 7 months, v e n t i l a t i o n improvements and changes i n chemical formulation o f the rubber r e s u l t e d i n a 200-fold reduction i n NMOR l e v e l s and e l i m i n a t i o n or reduction o f other nitrosamines a t most s i t e s . Results are shown i n Figure 2, and Table I .


3

3

3

Personal (breathing zone) a i r samples obtained i n October 1979, showed feed m i l l and c a l e n d e r i n g operators t o be most h e a v i l y exposed t o nitrosamines; one worker had a time-weighted average NMOR exposure o f 25 yg/M . Workers i n other hot process such as warm-up m i l l s , extruding machines, and c u r i n g processes were determined to have s u b s t a n t i a l personal exposure to airborne nitrosamines (Table I I ) . Personal exposures t o airborne NMOR and NDMA were a l s o detected i n the truck t i r e b u i l d i n g and t i r e shipping area. Although these nitrosamine l e v e l s are not very high (1.9 yg/M NMOR, 0.1 yg/M NDMA), they demonstrate the r e s i d u a l e f f e c t o f nitrosamines s t i l l v o l a t i l i z i n g o f f from storage o f f r e s h l y cured t i r e s . When compared t o passenger t i r e b u i l d e r s , truck t i r e b u i l d e r s on the average had 3 times the NMOR exposure even though 4 t o 5 passenger t i r e s could be b u i l t t o every truck t i r e . 3

3

3

By November, 1979, there were strong i n d i c a t i o n s that the source o f the high l e v e l s o f airborne NMOR was the thermal decomposition o f the r e t a r d i n g agent NDPhA, and the subsequent r e a c t i o n o f i t s n i t r o s o group with other rubber a d d i t i v e s (preformed morpholino compounds). The r e s u l t s were most s t r i k i n g when two short term a i r samples were c o l l e c t e d from the f e e d m i l l and calendering area - one rubber batch contained NDPhA, and the other d i d not. NMOR l e v e l s from the NDPhA batch were 14 times higher (120.3 yg/M ) than the rubber batch without NDPhA (NIOSH Interim Report No. 2, HE 79-109). In December 1979, v e n t i l a t i o n improvements (3-sided canopy enclosures and new fan motors) to the feed m i l l s which process rubber f o r the calendering o f b i a s - p l i e s , and i n s t a l l a t i o n o f l o c a l exhaust on the top and bottom o f the t i r e tread e x t r u s i o n 3



NMOR NDMA NPYR NDPhA NMOR NDMA NPYR NDPhA

Extruders

Curing Room

6.4 0.2 N.D. N.D.

32 4.4 N.D. N.D.

5.2 0.7 N.D. N.D.

NMOR NDMA NPYR NDPhA

Warm-up M i l l s

2.1 0.1, N.D. N.D.

—

64 1.6 2.0

— — — —

— —

---

— — N.S. N.S. N.S. N.S.

2.0 — 0.1 .07 N.D. — N.D. — 5.3 0.2

N.S. N.S. N.S. N.S.

N.S. — N.S. N.S. N.S. —

N.S. — N.S. — N.S. — N.S. —

— — —

—

--

— —

--

—

4.6 2.7

—

14 5.5 N.D. N.D.

--

--

— —

N.S. N.S. -N.S. — N.S. —

0.3 0.1 N.D. N.S.

1.0 0.3 ---

25 0.4 0.6

—

--

— —

1.3 0.8 N.D. N.D.

63 1.1 1.0 N.S.

N.S. N.S. N.S. N.S.

N.S. N.S. — N.S. — N.S. —

N.S. N.S. — N.S. — N.S. —

120 2.9 3.9 12

N.S5 N.S. N.S. N.S.

18

— —

3.5 0.4

—

160 1.5 2.3

— — —

1.8

Aug. '79 Oct. '79 Dec. '79 Feb. '80 Highest/Avg. Highest/Avg. Highest/Avg. Highest/Avg.

250 1.9 3.4 N.D.


Nitrosamines

3

Area and Process Samples in /xg/M °


Feed M i l l & Calender

Banbury

Location

Table I.



-

N.S. N.S. N.S. N.S. N.S. N.S. N.S. N.S.

NMOR NDMA NPYR NDPhA NMOR NDMA NPYR NDPhA

Lunch Room

Outside P l a n t

N.D. N.D. N.D. N.D.

Trace .02 N.D. N.S,

0.6 0.1 N.D. N.D.

— — — —

-— — —

— -— —

fl

3

μ%ΙΜ = micrograms per meter cubed.

D e t e c t i o n L i m i t : 1 p a r t per b i l l i o n

3

N.D. = Not Detected N. = Not Sampled

T r a c e :

A Health Hazard Evaluation of Nitrosamines in a Tire Manufacturing

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