Potential halogenated industrial carcinogenic and mutagenic chemicals

The Science of the Total Environment, 11 (1979) 259--278 259 © Elsevier Scientific Publishing Company, Amsterdam - - Printed in The Netherlands

POTENTIAL HALOGENATED INDUSTRIAL CARCINOGENIC AND MUTAGENIC CHEMICALS IV. HALOGENATED A R Y L DERIVATIVES

LAWRENCE FISHBEIN

National Center for Toxicological Research, Jefferson, A R 72079 (U.S.A.) (Received July 14th, 1978)

ABSTRACT

A variety of halogenated aryl derivatives possess significant activity as solvents for pesticides, h e a t transfer agents, pesticide intermediates, additives for rubber products, intermediates in organic synthesis and as insect repellants and deodorants. Ortho- and para
A. C H L O R I N A T E D B E N Z E N E S

Chlorinated benzenes are formed progressively and simultaneously when chlorine reacts with benzene at elevated temperatures in the presence of chlorination catalysts [1]. Once substitution occurs, the chlorine constituents exert an orienting effect on further chlorine atoms entering the ring resulting in certain isomers being preferrentially formed [I]. Most aryl halides are usually m u c h less reactive than alkyl or allyl halides toward nucleophilic reagents in either SN 1- or SN2-type reactions [2]. Chlorinated benzenes are composed of twelve chemical species: one mono-, three di-, three tri-, three tetra-, one penta-, and one hexachlorobenzene. Most of these are not only important intermediates for the production of many kinds of chemicals but they are also extensively employed singly or in combination in the home, industry, and agriculture for a variety of applications including: solvents for pesticides, heat-transfer agents, insect repellants, pesticides, deodorants and as additives for rubber products.

260 1. Chlorobenzene Chlorobenzene (monochlorobenzene;

) is used principally as

illustrated in the U.S. consumption pattern in! 1974 [3]: for pesticides and degreasing operations, 49%; as intermediate for production o f chloronitrobenzenes (in dye and pesticide intermediates), 30%; intermediate for diphenyloxide synthesis, 8%; intermediate for DDT production, 7%; o t h e r uses, 6%. U.S. Production of chlorobenzene in recent years has been as follows (millions of pounds): 1974 (379); 1975 (306) and 1976 (329). U.S. imports totaled 1.49 million pounds in 1974 and 8.37 million p o u n d s in 1975 [3]. It is estimated that the consumption of chlorobenzene will grow at an average annual rate of 1--2% in the U.S. provided governmental regulations do not significantly restrict its use as a solvent for pesticides [3]. 2. ortho.Dichlorobenzene ortho-Dichlorobenzene

(1,2-dichlorobenzene;

o
DCB;

has been produced commercially in the U.S.A. for over 50 years, primarily by procedures involving the chlorination of benzene or m o n o chlombenzene. Mixtures of the dichlorobenzenes can be p r o d u c e d b y chlorination of chlorobenzene at 150--190°C in the presence of ferric chloride [1,4]. The two principal dichlorobenzenes in the residue or in t h e mixture can be separated by fractional distillation or by crystallization o f t h e para-isomer. When chlorinated in the presence of a l u m i n i u m analogs chlorobenzene yields a mixture of o- and p-dichlorobenzenes plus .a very small amount of the meta4somer. A technical-grade of o r t h o . d i c h l o r o b e n z e n e aw~dlable in the U.S.A. typically contains 98.7% by weight of the o r t h o isomer and 1.3% of the meta- and para-isomers combined. Other grades o f ortho-dichlorobenzenes are also available, e.g., one typically contains 83% o f t h e ortho4somer, and 17% of the meta- and para-isomers combined. - The estimated U.S. Consumption pattern for ortho-dichlorobenzene in 1 9 7 5 was: 65% in organic synthesis (mainly for 3,4-dichloroaniline); 15% as a toluene diisocyanate process solvent; 10% for miscellaneous solvent usage (e.g., paint removers, engine cleaners, and de-inking solvents); 5% in d y e manufacture; and 5% for miscellaneous uses[3]. ortho-Dichlorobenzene is also used to manufacture three dyes: C. I. Morda n t Red 27, C. I. Direct Blue 108, and C. I. Direct Violet 54. Additional uses include: as a pesticide, in degreasing agents, in wood preserving c o m p o u n d s , as a heat-exchange medium and in an emulsifiable form for d e o d o r i z i n g garbage and sewage [5]. The patented applications for o r t h o dichlorobenzene include: in dyeing of natural and synthetic fibers [ 6 ] ; d y e i n g of polyolefin products [7] ; in phenol-resin adhesives [8] ; in lubrica n t s for metal working [9]; in compositions for dissolving p e t r o l e u m sedim e n t s [10] and as a transparency improver for acrylonitrile polymers [ 1 1 ] .

261 U.S. production of ortho-dichlorobenzene in 1972 was 28 million kg and in 1973 it was predicted to be between 32--41 million kg [4]. Although combined production o f ortho- and para-dichlorobenzene in western Europe in 1972 was estimated to have been approximately 30 million kg, it was not known how much was ortho-dichlorobenzene, ortho-Dichlorobenzene is produced in western Europe in the following countries (the number of producers is given in parentheses): The Federal Republic of Germany (4); France (2); Italy (1). Spain (1). and the United Kingdom (2) [4,12]. It is estimated that in Japan, 6 manufacturers produced 11 million kg in 1972 [4] and about 8 million kg in 1973 [13]. Future growth in production of ortho-dichlorobenzene in the U.S.A. is estimated to depend principally on the market for the organic chemicals which are manufactured from it. In this regard, the principal derivative is believed to be 3,4-dichloroaniline which is a key intermediate in the production of the amide herbicide, propanil (3'4'-dichloropropionanilide) and the two urea herbicides, diuron (3- [ 3,4-dichlorophenyl] -1,1-dimethyl urea) and neburon(1-n-butyl-3-[ 3,4
262 arene oxides may be precursors of the excreted metabolites, and that t h e s e arene oxides may also be responsible for the differing biological properties o f the parent compounds [22].

3. para-Dichlorobenzene

_ ~

1,4-dichlorobenzene; p-dichlorobenzene; C1

C1

has also been produced commercially in the U.S.A. for over 50 years by procedures involving the chlorination of benzene or m o n o c h l o r o b e n z e n e essentially as described earlier for ortho-dichlorobenzene [1,2]. F o r h i g h e r yields of the para-dichlorobenzene isomer an "orienting" catalyst such as an arylsulphonic acid can be employed [2] or alternatively chlorination can b e carried out further to convert the ortho-isomer to 1,2,4-trichlorobenzene from which the para-dichlorobenzene can be separated by distillation [1,2 ] . para.Dichlorobenzene is mainly used as a m o t h repellant, mildew c o n t r o l agent and as a space deodorant [23--25]. Other areas of utility include: as an intermediate in the production of dyes, insecticides, pharmaceuticals a n d organic chemicals [2,23,26], as a catalyst for manufacture of m e r c a p t o acids [27] and as an intermediate in the production of p o l y p h e n y l e n e sulfide resins [2] and the dye intermediate 2,5~lichloroaniline [ 2 6 ] . U.S. Production of para~lichlorobenzene was 45.8 million p o u n d s a n d the 1976 production is estimated to have been 70 million pounds. T h e estimated U.S. consumption pattern for para dichlorobenzene in 1975 was: 50% as a space odorant; 40% for moth control; and 10% for miscellaneous growth [3]. para-Dichlombenzene is produced in western Europe in the following countries (the number pf producers is given in parentheses): t h e Federal Republic of Germany (4); France (3); Italy (3) and the United Kingdom (2) [4,12]. Production of para-dichlorobenzene by the 6 Japanese manufacturers is estimated to have been 16 and 18 million kg in 1972 [4] and 1973 [ 1 3 ] , respectively. T h e current OSHA environmental standard for para-dichlorobenzene is 75 p p m (450 mg/m 3 ) for an 8-h time-weighted exposure in a 40-h w o r k w e e k [14]. The hygienic standards for permissible levels of para-dichlorob e n z e n e in various countries were as follows (mg/m 3 ) [ 1 5 ] : Federal Republic of Germany, 450; Democratic Republic of Germany, 200; t h e MAC in the U.S.S.R. is 20 mg/m 3 . O n l y limited information is available on the level of chlorinated benzenes in air and water. Chlorinated benzenes are more volatile than the PCBs a n d h e n c e they are more likely to constitute atmospheric contaminants, (especially the lower-chlorinated benzenes)[13], para-Dichlombenzene has b e e n d e t e c t e d in ambient air in and outside the Tokyo metropolitan area at levels of 2.7--4.2 and 1.5--2.4 pg/m 3 , respectively. As might be anticipated f r o m its use, para.dichlorobenzene concentrations were higher indoors (e.g., 105-1 7 0 0 pg/m 3 ) [28]. Levels of para-dichlorobenzene averaging 1.0, 1.1 a n d

263 1200 ppb have been detected in intake, effluent and activated sludge samples respectively in several.sewage plants in Tokyo [13]. Although para~lichlorobenzene has been detected in several kinds of fish, e.g., 0.1 ppm in carp, 0.04 ppm in harvest fish and 0.05 ppm in horse mackeral, on the basis of fat content, the level is generally low. Human fat contains both para-dichlorobenzene and PCBs at roughly equal concentration (ca. 2.1--2.3 pg/g) while the level of para-dichlorobenzene in human blood samples is three times higher than that of PCBs (e.g., 9.5 and 2.9 ng/ml respectively [28]. It should be noted that the industrial output of para-dichlorobenzene in Japan tripled in the past decade from 8800 tons in 1963 to 22,000 tons in 1972, far exceeding the peak production of polychlorinated biphenyls (e.g., 7000 tons in 1970), an ubiquitous environmental pollutant. Hence, it was suggested that a good proportion of para-dichlorobenzene is dispersed into the environment as a pollutant of biota, considering the amount of production, type of application, its high volatility and affinity to fatty tissues [28]. There is a paucity o f information regarding the carcinogenicity of the dichlorobenzenes. Five cases of blood disorders (including 2 cases of chronic lymphoid leukemia, 2 cases of acute myeloblastic leukemia and 1 case of myeloproliferative syndrome) were found in subjects exposed to ortho-or para-dichlorobenzenes as a solvent for other chemicals or in chlorinated benzene mixtures [4,29]. In the two cases with chronic lymphoid leukemia, one subject was exposed to a glue containing 2% ortho-dichlorobenzenefrom 1945--1961 and the other was exposed from 1940--1950 to a solvent used for cleaning electrical parts which contained ortho-,meta-and para-dichlorobenzenes at levels of 80%, 2% and 15%, respectively [4,29]. This suggested association between leukemia and exposure to dichlorobenzenes was considered as insufficient evidence by IARC.[4] from which to assess the carcinogenic risk of the dichlorobenzenes. No information appears available on the mutagenicity of the isomeric dichlorobenzenes. In man, para-dichlorobenzene is converted to 2,5-dichlorophenol and 2,5
4. 1,2,4-Trichlorobenzene _ ~ 1,2,4-Trichlorobenzene(unsyrn-trichlorobenzene; TCB; CI

C1) is

prepared from 2,4- or 2,5- or 3,4
264 No definitive information is available as to the amounts of TCB produced, nor are there data as to its carcinogenicity and/or mutagenicity. Coate et al. [33] reported that chronic inhalation exposure of rats, rabbits and monkeys to 25.0, 50.0 and 100.0 ppm of TCB for 26 weeks. Microscopic changes were seen in the parenchymal cells of livers and kidneys from all groups of rats exposed to TCB when sacrificed after 4 and 13 weeks o f exposure, but not exposure-related abnormalities or other effects were seen after 26 weeks of exposure in any species. TCB is slowly metabolized to yield glucuronide and sulfate conjugates of 2,3,5- and 2,4,5-trichlorophenols [34] The hepatotoxicity of halobenzenes appears to be directly related to their bio-transformation products, and the severity of hepatic necrosis appears to depend upon the rate at which the active metabolite is formed [ 3 5 ] . While the major toxic metabolites appear to be epoxides, it is known t h a t hepatic cells can convert these toxic epoxides to biologically inactive metabolites via epoxide rearrangement [36], enzymic addition of water to f o r m catechols [37] and enzymic conjugation with glutathione (GSH) and ultim a t e excretion as a mercapturic acid [38]. The steady-state concentration o f the epoxide in the liver depends on its rate of formation, versus the rate at which it is converted to the phenol, GSH-conjugate and the dihydrodiol. When the concentration of the epoxide is high, it appears to bind covalently to hepatic macromolecules [39]. It has been stated that the substitution of chlorine in the benzene ring increases the systemic toxicity with each clorine atom up to two, and t h a t further chlorination reduces the toxicity [40]. The systemic toxicity of TCB is thus believed to lie between para-dichlorobenzene and the m o r e chlorinated benzene compounds, on the one hand, and ortho-dichlorobenzene and chlorobenzene on the other hand, being more toxic than the f o r m e r compounds and less toxic than the latter [33]. Conte et al. [33] suggested a TLV of 5 ppm be set for 1,2,4-trichlorobenzene. C1

5. Hexachlorobenzene Hexachlorobenzene (perchlorobenzene; HCB; C1

C1 ~1

is an

C1 C1 additional chlorinated benzene of increasing toxicological and environmental c o n c e r n [13,41--44]. The latter concern is based on the potential of HCB f o r bioaccumulation and environmental persistence. HCB is a hazardous c o m p o n e n t of certain industrial chemical wastes. Table 1 lists the industries identified as possible HCB sources and potential origin of HCB wastes [ 4 3 ] . T h e chlorinated solvents and pesticide industries were found to account for n e a r l y all HCB wastes produced (approximately 8.5 million pounds per year in solid wastes and liquid effluents) by the 14 industries surveyed as sources o f HCB wastes [41--43]. Table 2 illustrates the estimated total quantity of HCB contained in U.S.

265 TABLE 1 INDUSTRIES I D E N T I F I E D AS POSSIBLE HCB SOURCES AND POTENTIAL ORIGIN OF HCB WASTES [43] Industry/type

Potential origin of HCB wastes

Basic HCB p r o d u c t i o n / d i s t r i b u t i o n

HCB production operation

Chlorinated solvents p r o d u c t i o n

Reaction side-product in the production of chlorinated solvents, mainly, carbon tetrachloride, perchloroethylene, trichloroethylene, and dichloroethylene

Pesticide production

Reaction side-product in the production of Dacthal, simazine, mirex, atrazine, propazine, and pentachloronitrobenzene (PCNB)

Pesticide formulation/distribution

Formulation, packaging and distribution of HCB-containing pesticides

Electrolytic chlorine p r o d u c t i o n

Chlorine attack on the graphite anode or its hydrocarbon coating

Ordnance and pyrotechnics production

Use of HCB in the manufacture of pyrotechnics, and trace bullets and other ordnance items

Sodium chlorate p r o d u c t i o n

Similar to electrolytic chlorine production where graphite anodes are used

Aluminium manufacture

Use of HCB as a fluxing agent in aluminum smelting

Seed treatment industry

Use of HCB in seed protectant formulations

Pentachlorophenol (PCP) p r o d u c t i o n

Reaction by-product of PCB production b y chlorination of phenol

Wood preservatives i n d u s t r y

Use of HCB as a wood preserving agent

Electrode manufacture

Use of HCB as a porosity control in the manufacture of graphite anodes

Vinyl chloride m o n o m e r p r o d u c t i o n

By-product in the manufacture of vinyl chloride monomer

Synthetic rubber p r o d u c t i o n

Use of HCB as a peptizing agent in the production of nitroso and styrene rubbers for tires

industrial wastes, by-products, and products in 1972 [42]. In the U.S.A. approximately 90% o f the HCB produced annually is as a by-product of 10 perchloroethylene, 5 trichloroethylene and 11 carbon tetrachloride manufacturing plants [ 4 1 , 4 2 ] . Most of the remaining HCB is as a by-product at more than 70 other manufacturing sites producing chlorine and certain pesticides. Approximately 420,000 pounds of HCB are used as a peptizing agent in the manufacture of styrene and nitroso rubber for tires and as a grain fungicide for seed treatment. Methods for the direct production of HCB are proprietary and hence limited information is thus available. Two major processes involve either benzene or benzene hexachloride as the principal raw materials [41,42].

266 TABLE 2 ESTIMATED TOTAL QUANTITY OF HEXACHLOROBENZENE CONTAINED IN U.S. INDUSTRIAL WASTES, BY-PRODUCTS, AND PRODUCTS IN 1972 [42 ] Product

U.S. Production in 1972 (1000 lb)

Estimated H C B Produced (1000 Ib)

High

Low

Perchloroethylene Trichloroethylene Carbon tetrachloride Chlorine Dacthal Vinyl chloride Atrazine, propazine, simazine Pentachloronitrobenzenc Mirex

734,800 427,000 997,000 19,076,000 2,000 4,494,000

3,500 450 400 390 100 27

1,750 230 200 160 80 0

112,000 3,000 1,000

9 6 2

5 3 1

Total

25,846,800

4,884

2,429

HCB can be produced industrially from some isomers of BHC b y o n e o f the followingprocesses:

C] CI~'~C1 (A)

(B)

CI.L~,,~C I Cl C1 Cl ~ C1 Cl~jgC]

300_400°C

--3HCI

~

302

CI'

C1 Cl

C1 CI[~C1

- CI~/JCI Cl

+ 3HCI

Cl C1 ~ C1 O2 '" Cll,,.k--ff/)CI+ 3HzO

atm

V

C1

C1

It is possible that with a process similar to (B), among the p r o d u c t s o f environmental degradation of BHC isomers, HCB may also be formed [ 4 5 ] . While hexachlorobenzene is used as a fungicide (primarily to control b u n t of wheat), it can be formed as an impurity during the synthesis of t h e w i d e l y used herbicide DCPA (dimethyltetrachloroterephthalate, Dacthal)which c a n c o n t a i n 10--14% HCB [46]. Pentachlorobenzene (PCNB, quintozene) a pesticide, contains 1 - 6 % HCB. HCB is also an intermediate in the p r o d u c t i o n of pentachlorophenol (PCP), a widely used herbicide and fungicide. Technical pentachlorophenol can contain up to 13% impurities, a part o f w h i c h could consist of residual HCB [47]. The estimated total q u a n t i t y o f HCB waste generated in the pesticide industry is 1.655 tons per year. T h e HCB is present mainly in tars and still bottoms from the m a n u f a c t u r i n g operations [43]. O f the total HCB generated by the chlorinated solvents industry, 92% is

267 discharged in the waste streams which are disposed of on land or are incinerated while only 8% (210 tons) of HCB are recovered for sale [ 4 3 ] . The prevalence of various disposal methods is shown in Table 3 in terms of HCB (and HCB-containing wastes) handled in the U.S.A., and the number of facilities (on-site and off-site) which utilize the disposal methods. The data in Table 3 indicate that, based on the total quantity of waste handled, land disposal is currently the most prevalent method for ultimate disposal of HCB waste. Among land disposal methods, the use of landfills is the most prevalent m e t h o d , accounting for the disposal of 56.8% of all HCB wastes. Ranked next to land disposal is incineration which accounted for the destruction of a m i n i m u m of 1,163 tons of HCB per year contained in a waste mixture in excess of 5,257 tons per year. Compared to land disposal and incineration, the quantities of waste discharged to sewage treatment plants and to the atmosphere appears to be very small [43]. Mismanagement of HCB wastes and use of products have resulted in several serious incidents of environmental contamination [ 48]. HCB has been found recently (with hexachlorobutadiene) in water, soil and selected aquatic organisms along the lower Mississippi River in Louisiana. Highest levels were found downstream from heavily industrialized areas [49]. Air immediately adjacent to production facilities has been shown to have concentrations from 1.0 to 23.6 # g / m 3 . HCB has also been identified in the municipal drinking water supply of Evansville, Indiana [50]. HCB has also been identified in surface water and industrial effluents in U.S.S.R., Germany, and Italy [45]. The average pollution levels differ greatly, e.g., from 2.5 p p t for Italian surface waters to 130 ppt for the waters of the River Rhine in Holland, which suggests both fungicidal and industrial as original sources of t h e contamination [45]. HCB has been found in the intake, effluent, and activated sludge in several sewage plants in T o k y o at average levels of 0.0013, 0.0011 and 38 ppb, respectively [28]. A major HCB contamination episode occurred in southern Louisiana .(U.S.A.) in 1972 where HCB levels were detected in beef cattle far in excess of the tolerance level o f 0.3 p p m in beef fat then in effect [51,52]. The source of HCB in these animals originated primarily from the industrial plants in the area which were engaged in the production of perchloroethylene, carbon tetrachloride, synthetic rubber, and agricultural chemicals (atrazine, simazine and propazine herbicides). HCB waste from at least two of these plants had been d u m p e d in off-site landfills. The hazardous characteristics of HCB have been well documented and include its potential for bioaccumulation in the food chain [13,53,54], environmental persistence due to physical, chemical and biological stability [13,41,42] a n d from its toxicity [13,41,42]. HCB has been f o u n d in fish from a number of river systems in Canada [55] and in t h e U.S,A. [56--58], in juvenile seals at levels of 0.067 p p m (wet wt.) collected in coastal waters off the Netherlands, [59]. In low levels in Japanese fish and shellfish [13], in wild birds in the Netherlands [60], and in the eggs of terns collected in Canada and in the Netherlands [57,61].

TABLE 3

Pesticide industry

Emission to atmosphere 19

100%

5.3

5.3

2,696 c

small; data on exact quantity not available not available

not available

1,163

750 b

213 a 200 not available

1,533

208 1,050 50 -225

100%

--

--

--

43.1

27.8

7.9 7.4 --

56.8

7.7 38.9 1.9 -8.3

% o f total

24,421 c

not available

not available

not available

5,257

1,000 b

3,991 a 266 not available

19,164

281 7,000 67 156 11,660

Quantity (tons/year)

100%

--

--

--

21.5

4.1

16.4 10.0 --

78.4

1.1 28.7 0.3 0.6 47.7

% of total

HCB-Containing wastes

aIncludes a very small quantity of HCB wastes (400 lb per year) from three plant sites engaged in chlorinated solvents manufacture. These wastes are extremely dilute (10 to 40 ppm HCB) and were not included in the total waste quantities in order to avoid gross distortion of "HCBContaining Waste Quantities" handled by incineration. bWaste quantities are based on 1970--71 data supplied by the off-site waste disposal contractor then handling the waste. Waste is assumed to contain 75 percent HCB based on data for other plants. CDoes not include 1,400 tons per year of HCB waste (1,750 tons of HCB-containing waste) temporarily stored under cover at one pesticide production site. Also does not include 210 tons of HCB which is recovered for sale from 284 tons of HCB-containing wastes at one chlorinated solvents plant.

Total

1

1

Pesticide formulation/ distribution

to waste treatment plants

Discharge

1

Chlorinated solvents

Resource recovery (excluding incineration) 5.3

42.1

8

21.0 10.5 5.3

42.1

5.3 15.7 5.3 5.3 10.5

(Subtotal)

4 2 1

8

1 3 1 1 2

Quantity (tons/year)

No.

% of total

HCB waste

Plant sites

5.3

Chlorinated solvents

Chlorinated solvents Pesticide industry Electrolytic chlorine

Chlorinated solvents Chlorinated solvents Pesticide industry Electrolytic chlorine Chlorinated solvents

Industry type

1

With by-product recovery

Incineration WithGut by-product recovery

(Subtotal)

Deep well disposal

Land disposal Sanitary landfill Industrial landfill

Disposal method

PREVALENCE OF METHODS USED F O R ULTIMATE DISPOSAL OF HCB WASTES [43]

b~ o0

269 Studies by Laseter et al have indicated that HCB is bioaccumulative in bass to levels 44,000 times the concentration of HCB in the surrounding aquatic environment [54]. HCB is very stable and lipophilic. The monitoring of human adipose tissues collected from across the U.S.A. has shown that approximately 95% of the populace has trace residues of HCB [62]. HCB residues have also been found in adipose tissue and blood samples in Australia, Japan, Turkey and United Kingdom [62--68]. In a study conducted in Louisiana, in 86 persons who resided in an HCB-contaminated area, the mean HCB concentration in plasma samples was 0.0036 ppm [66]. A group of farm workers in the U.S.A. occupationally exposed to HCB-contaminated Dacthal had blood HCB concentrations averaging 0.040 ppm, but there was no evidence of porphyria in this group [69]. An Australian study of occupationally exposed individuals showed levels ranging from 0 to 0.095 ppm [65]. Another Australian study showed that all perennial fat samples examined contained HCB at an average concentration of 1.25 ppm with a range from a trace to 8.2 ppm [63]. Human adipose tissues from Japan contained HCB levels ranging from 0.38 to 1.48 ppm in one study [62] and 0.10 to 0.42 ppm with a mean of 0.21 ppm in a later study [70]. Significant residues o f HCB have been reported in human milk from the Netherlands [71]. Australia [72]. Germany [64] and Sweden [75]. For example, levels of HCB ranging from 0.07 to 0.22 ppm (on a fat content basis) have been found in breast milk from samples in Sweden [73]. In Turkey, HCB was the causative agent in a severe outbreak of porphyria cutanea tarda symptomatica involving several thousand people in 1955 and 1959 [67,74,75]. The doses of HCB ingested were estimated to have been 1 to 4 mg/kg for several months to two years [67]. The carcinogenic activity of HCB in Syrian golden hamsters was recently demonstrated by Cabral et al. [76]. Doses ranging from 50 to 200 ppm of HCB administered in t h e diet for life resulted in a significant induction of hepatomas, haemangio-endotheliomas and thyroid adenomas. Further, an increased number of tumor-bearing animals and of tumors per animal was noted, as were a shortened lifespan and a reduced latency period for onset of liver tumors. These effects may indicate that HCB behaves like certain carcinogens shown to have multipotential activity [76]. Cabral et al. [76] in a purely quantitative approach indicated that an intake of 4--16 mg/kg/day of HCB in their hamster studies above was within the range of the estimated quantities accidently consumed by the Turkish people for several months at a time resulting in severe toxic porphyria [ 67 ]. The carcinogenicity o f HCB has also been demonstrated recently in Swiss mice fed for life a diet containing 50, 100 and 200 ppm., The hepatoma incidence was 10% in b o t h males and females treated with the median dose of HCB, and 29.7 and 14.0% respectively, in females and males treated with the highest dose of HCB; None of the hepatomas metastasized or occurred in the control group [77].

270 HCB has been found mutagenic in Saccharomyces cerevisiae (Ceppo 6 3 2 / 4 strain) using reversion from histidine and methionine as a measure of t h e induced mutation [78]. HCB at doses of 70 or 221 mg/kg did not induce dominant lethal m u t a tions in the rat [79]. HCB-pretreatment of rats led to an increase in liver microsomal 2,4-diamino-anisole activation to a mutagen [80] (when t e s t e d by the Ames assay in Salmonella) [81] after a dose of 10 mg/kg i.p. and t o an increase in ethylmorphine N-demethylase after a dose of 50 m g / k g i.p. Recently, evidence was reported [82--85] for the urinary excretion o f the metabolites pentachlorophenol, 2,4,5-trichlorophenol, t e t r a h y d r o hydroquinone and pentachlorothiophenol in the rat following administration of HCB. (However, no urinary phenolic metabolites of HCB have been f o u n d in rabbits [86] .) Mehendale et al. [83] also identified pentachlorobenzene and tetrachlorobenzene as HCB metabolites in the rat and found that t h e reductive dechlorination of HCB was catalyzed by an enzyme located in t h e microsomal fraction of liver, lung, kidney and intestine. It was also r e p o r t e d that 70% of the total dose was found remaining 7 days after administration [83]. Following a single dose HCB to male Wistar rats, the biological half-life was estimated to be about 60 days [87]. Aspects of the nature of the trace contaminants in commercial HCB bears particular emphasis. For example, Villaneuva et 81. [88] reported hepta- a n d octadichlorodibenzofurans, octachlorodibenzo-p-dioxin, octa-, and nonaand decachlorobiphenyls, 1-pentachlorophenol, 2,2-dichloroethylene, hexacyclopentadiene, pentachloroiodobenzene and heptachlorotropflium in trace a m o u n t s in various samples of commercial HCB. The toxicities of some o f t h e chlorinated dibenzo-p-dioxins and chlorobenzofurans have been reported [89---93] 6. Brominated Benzenes

The extent of industrial utilization of brominated (as well as iodinated) benzene derivatives are relatively small compared to their chlorinated analogs. In general, very much less is known of their environmental and health effects. a. Bromobenzene. Bromobenzene (phenylbromide; ~(,_fl~--Br) is prepared industrially by the action of bromine or benzene in the presence of iron p o w d e r . It is used as a chemical intermediate (e.g., for the preparation o f Grignard reagents such as phenyl magnesium bromide); as an additive for m o t o r oil, and as a solvent for crystallization on a large scale where a heavy liquid is required. The production of bromobenzene in the years 1972--197 5 was estimated to be greater than 500 kg per year [94]. N o occupational standard for bromobenzene has been established by OSHA. Bromobenzene has been detected by EPA in tap water from New Orleans, a l t h o u g h no quantitative measurement was reported [95]. N o animal carcinogenicity studies have been reported for bromobenzene.

271 When tested at doses ranging from 10--750 pg/plate, it was inactive in S. typhimurium TA 100, TA 98, TA 1535 and TA 1537 with metabolic activation by liver S-9 fractions from Aroclor-pretreated rats [96]. Bromobenzene was also inactive when tested in vitro with S. cerevisiae D3 [97] but mutagenic when tested in the host-mediated assay with S. cerevisiae D3 [98]. Bromobenzene is inactive in the transformation of Golden Syrian hamster embryo cells [99]. Bromobenzene appears to be rapidly absorbed and metabolized in animals. T h e urinary metabolites which have been detected in animals include: 2-bromophenol, 3-bromophenol, 4-bromophenol, bromocatechol, bromophenyldihydrodiol and p.bromophenylmercapturic acid 11194,100, 101]. Glucuronide and sulfate conjugates of the bromophenols, bromocatechol and dihydrodiol are also formed; the proportion of metabolites excreted is species dependent [101]. Bromobenzene has been demonstrated in vitro and in vivo to bind with liver proteins in rats when liver glutahione levels have been extensively depleted. This suggests that bromobenzene is initially activated to an electrophile (bromobenzene-3,4-oxide) and conjugated with glutathione in the liver [100], or can alkylate cellular macromolecules in the liver [94]. This epoxide may also be excreted in the bile and be reabsorbed through the enterohepatic circulation [ 102 ]. b. para-Dibromobenzene, para-Dibromobenzene (1,4-dibromobenzene; B r - - ~ G ~ - - B r ) is prepared by the catalytic bromination of benzene. It is * ~ , ~ = = = = = d

used principally as a chemical intermediate in the production of drugs, dyestuffs and other organic compounds. Production of para-dichlorobenzene is believed to significantly greater than 500 kg/year [94]. No occupational standard for para-dibromobenzene has been established b y OSHA or have there been TLV's or MAC's adopted elsewhere. An unspecified isomer of dibromobenzene has been detected in finished drinking water at three locations and in one sample of river water as reported in recent EPA surveys [ 9 5 ] . No information appears to be available on the carcinogenicity and mutagenicity of para~libromobenzene. Data on the biotransformation of para-dichlorobenzene suggests that it may be metabolically activated via an arene oxide to a potential electrophile. Two major metabolites, 2,4- and 2,5-dibromophenol were identified in the urine and to a lesser e x t e n t in the feces of rabbits given single i.p. injections of 50mg/kg of para-dibromobenzene. It was suggested, that paradibromobenzene is metabolized to the phenols via formation of 1,2-arene oxide, which is then cleaved to yield the 1- or 2- carbonium ion intermediate. A 1,2-H or 1,2-Br shift then yields the dienone, which then enolizes to yield 2,4- or 2,5-dibromophenol [101,103]. It should also be noted that 2,4-dibromophenol has been found to be a tumor promoter in mouse skin [102].

272 7. Benzyl halides Most aryl halides are usually much less reactive than alkyl or allyl halides toward nucleophilic reagents in either SN1- or SN2-type reactions. However, in contrast to phenyl halides, benzyl halides are quite reactive, are analogous in reactivity to allyl halides and are hence readily attacked by n u c l e o p h i l i c reactants in both SN1- and SN2-displacement reactions. This reactivity is related to the stability of the benzylcation, the positive charge o f which is expected to be extensively delocalized [104]. a. Benzyl chloride. Benzyl chloride ( ~ -

CH2C1; c h l o r o m e t h y l b e n z -

ene; c~-chloroto!uene) is made by the chlorination of toluene a n d is used principally (65--70%) in the U.S.A. as an intermediate in the m a n u f a c t u r e o f butylbenzylphthalate, a vinyl resin plasticizer, while the remaining 30--35% is employed as an intermediate in the production of benzyl alcohol, quaternary ammonium chlorides and benzyl derivatives such as benzyl acetate, cyanide, salicylate and cinnamate, which are used in perfumes a n d pharmaceutical products [105]. Suggested uses of benzyl chloride include: in the vulcanization of fluororubbers [106] and in the benzylation of p h e n o l and its derivatives for t h e production of possible disinfectants [107]. Annual production o f benzyl chloride is estimated to be in excess of 100,000 kg per year in the U.S.A. [3]. The current OSHA environmental standard for benzyl chloride is 1 p p m , (5 mg/m 3 ) for an 8-h time-weighted exposure in a 40-h w o r k w e e k . The hygienic standard for permissible levels of benzyl chloride in t h e working environment in various countries were as follows (mg/m 3 ) [15] : Federal Republic of Germany, 5; Democratic Republic of Germany, 5; t h e MAC in t h e U.S.S.R. is 0.5 mg/m 3 . Benzyl chloride has been shown to induce local sarcomas in rats treated by subcutaneous injection [108,109]. Benzyl chloride was reported to be weakly mutagenic in S. typhimurium T A 100 strain [110]. It is active at doses of 0.1, 1.0 and 10.0/~g/ml in t h e transformation of Golden Syrian hamster embryo cells [99].

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Note added in proof A d m i n i s t r a t i o n o f h e x a c h l o r o b e n z e n e in a diet at levels o f 10 a n d 50 p p m t o I C R mice f o r 24 w e e k s did n o t result in t h e i n d u c t i o n o f t u m o r s in t h e liver o r a n y o t h e r o r g a n s , a l t h o u g h m o s t t r e a t e d animals e x h i b i t e d h y p e r t r o p h y o f t h e c e n t r i l o b u l a r area o f t h e liver. A l t h o u g h HCB a l o n e had n o e f f e c t , it e n h a n c e d t h e i n d u c t i o n o f liver t u m o r s b y p o l y c h l o r i n a t e d terp h e n y l (PCT) w h e n b o t h were a d d e d t o a diet at 50 a n d 250 p p m , respectively [ 1 1 1 ] . H e n c e , H C B a n d PCT w e r e suggested t o be acting synergistically

278 on the liver. Alternatively, since HCB causes enlargement of centrilobular hepatocytes due to induction of drug-metab01izing enzymes and also increases the s m o o t h endoplasmic reticulum, changes in drug-metabolizing enzymes which may enhance the carcinogenicity of PCT. Benzyl chloride (C6 Hs CH: C1), benzotrichloride (C6 Hs CC13 ), benzal chloride (C6Hs CHC12 ) and benzoyl chloride (C6Hs COC1) were r e c e n t l y surveyed for their mutagenicity in microbial systems such as rec-assay suing B. subtilis and reversion assays using E. coli WP-2 and Salmonella typhimurium T A strains with and without metabolic activation in vitro [ 1 1 2 ] . Benzyl- and benzal chloride as well as benzotrichloride were positive in t h e me-assay. Benzotrichloride and benzal chloride required metabolic activation for their mutagenic activities in several strains of E. coli (WP-2 her) and S. typhimurium TA 1535, TA 100 and TA 98. The mutagenie metabolites o f these compounds may n o t have been produced by hydrolysis. Benzyl chloride was weakly mutagenic in WP-2 her as well as TA 100 w i t h o u t S-9 metabolic activation. Benzyl chloride is known to alkylate bases, and t h e reaction may occur without metabolic activation [112]. Benzoyl chloride exhibited no mutagenic activity in the above detection procedures employed. This might be due to its high susceptibility to hydrolysis. The hydrolysis compounds of benzotrichloride, benzal chloride or benzyl chloride are benzoic acid, benzaldehyde and benzyl alcohol respectively. W h e n these hydrolysis compounds were tested in WP-2 her and T A 100, no activity comparable to the original chlorinated precursors was observed for any o f therm The mutagenic metabolite of benzotrichloride is believed t o be possible intermediate(s) between benzotrichloride and benzoic acid. It'should be n o t e d that a significant increase in the incidence of cancer has been r e p o r t e d a m o n g workers engaged in the production of benzoyl chloride [ 1 1 3 ] . The mutagenicities of benzotrichloride, benzal chloride and benzyl chloride (intermediate products in the benzoyl chloride production process) correlated well with their observed carcinogenicities in mice [113, 114]. NIOSH has recently recommended a ceiling value of benzyl chloride o f 5 m g / m 3 of air based on a 15-min sampling period instead of t h e present limit of 5 m g / m 3 as a time-weighted average concentration for up to a 10-h workshift, 40-h workweek. It is estimated that about 3,000 workers in t h e U.S.A. are exposed to benzyl chloride [115].