# v SUMMARY AND CONCLUSIONS
Exposure to chrysene as an isolated chemical presently occurs only in specific occupations, i.e., chrysene synthesis, laboratory experimentation, and possibly in the synthesis of anthraquinone vat dyes. However, chrysene and its derivatives, e.g., certain methylchrysene isomers, along with hundreds of other polycyclic aromatic hydrocarbons (PAH's), are formed during the pyrolysis of organic matter and can occur in any occupational environment where this process takes place. While it has been suggested that 700 C is the optimum pyrolytic temperature for PAH-formation, other factors such as the chemical and physical nature of the pyrolyzed material, the presence or absence of oxygen, and the period of tine during which the compound is pyrolyzed also determine the amounts and mixtures of various PAH's formed. Chrysene has been detected in many materials which result from, or are used in,industrial processes. Chrysene also has been detected in the ambient atmosphere and in certain food products.
A number of experimental animal studies have been conducted for the purpose of assessing the carcinogenicity of chrysene, with varying results.
When three 100(u)g doses of chrysene were administered by subcutaneous (s.c.) injection to newborn mice, an increased incidence of liver tumors was observed.
The increase, however, was not statistically significant.
Marginal results were obtained when mice were injected (s.c.) with 1 mg chrysene in arachis oil, once a week, for 10 weeks. This treatment resulted in the development of injection-site tumors in 2 of 20 animals.
Tumors also developed after chrysene (1% solution in acetone) was applied to the shaved backs of mice. Chrysene appears to exert a stronger carcinogenic effect when used as a tumor initiator than when used as a "complete" carcinogen, e.g., when the shaved backs of each of 20 mice were painted with ten doses of 0.1 mg chrysene (each in 0.1 ml acetone), followed by treatment with tetradecanoyl phorbol acetate (TPA) ,11 of the 18 surviving mice had tumors (total of 19 tumors) after 20 weeks. Similar results were obtained using chrysene (total dose of 4.4 micromoles) either as an initiator with TPA, or when chrysene (1.0 mg in 0.4 ml acetone) was painted on the shaved backs of mice prior to treatment with croton resin.
Chrysene also has produced positive results in mammalian cell transformation tests and in the "Ames" test for mutagenicity.
Certain methylchrysene isomers have also been shown to possess carcinogenic potential: 5-methylchrysene has been reported to be a strong "complete" carcinogen as well as a stronger tumor initiator than chrysene.
Epidemiologic evidence for the carcinogenicity of chrysene as an isolated chemical was not located. However, certain industry-related materials which contain many PAH's, including chrysene and its methyl derivatives, Chrysene may be generated inadvertently in numerous industrial processes which involve the pyrolysis of organic matter. Further, conditions which are favorable for the formation of chrysene also are likely to be favorable for the formation of methylchrysenes and numerous other PAH's whose carcinogenic potencies range from greater than to less than that of chrysene. While the aforementioned control measures may be applied to the general class of PAH's, NIOSH recognizes that under certain circumstances of PAH-exposure, they will be neither appropriate nor feasible.
While no workplace environmental limit for chrysene is recommended at this time, information on analytical methodology is included in this review.
Most methods for the identification and quantitation of chrysene involve various forms of chromatography and spectrometry.

# INTRODUCTION
The carcinogenic potential of certain polycyclic aromatic hydrocarbons (PAH's), e.g., benz(a)pyrene and benz(a)anthracene, has been well
documented (IARC Monograph, Volume 3, 1973;Dipple, 1976). However, comparatively little information exists upon which to base an evaluation of the carcinogenic potential of chrysene. Further, isolated exposure to chrysene occurs only in specific operations, i.e., chrysene manufacture, laboratory experimentation, and possibly in the synthesis of anthraquinone vat dyes. The number of workers thus exposed is small relative to the number of workers exposed to chrysene ad-mixed with other PAH's in industrial processes which involve the pyrolysis of organic matter. This notwithstanding, sufficient quantities of chrysene may now be in use to elicit concern over any biological effects exerted by this chemical. Thus, an integration and evaluation of all experimental data pertinent to the carcinogenic potential of chrysene appears warranted.
There is now no federal occupational health standard for chrysene, or

# II. COMMON OPERATIONS, USE, AND OCCURRENCE
A'. Workplace Environment PAH's are perhaps the most ubiquitous of the carcinogenic agents that have been detected in the atmosphere. Chrysene, along with other PAH's, occurs most frequently as an adsorbate on airborne particulates resulting from the pyrolysis of carbonaceous materials (Filatova et al., 1972).
Chrysene is sometimes encountered as a vapor. The yield of chrysene can be affected by the chemical and physical nature of the pyrolyzed compound, the pyrolysis temperature, the presence or absence of adequate oxygen for complete combustion, and the period of time during which the compound is exposed to heat. Experimental determinations have shown the optimal temperature for PAH formation to be around 700 C (Masuda et al., 1967).
From an occupational health standpoint it is important to identify the sources of these compounds. Table I lists some of these sources for chrysene.  Cleary, 1963Qazi and Nau, 1975Cleary, 1963Rhee and Bratzler, 1968 Lijinsky et al., 1963Lijinsky and Raha, 1961Filatova et al., 1972Tye et al., 1966Hendrickson et al., 1963Falk et al., 1951 *Unless otherwise stated, the units (ppm) refer to parts of chrysene per million parts of source material sampled, as a weight/weight ratio.

# B. Occupational Areas of Concern
At present, it is believed that exposure to chrysene as an isolated chemical occurs only in specific occupations, i.e., in chrysene manufacture, laboratory experimentation, and perhaps in the synthesis of anthraauinone vat dyes. It was Holbro (1953) who suggested the use of chrysene as a starting material in the synthesis of dyestuffs, particularly of anthraquinone vat dyes, to which the results of his research showed chrysene imparted favorable properties regarding "affinity, shade, and fastness". While the scope of this report is limited primarily to chrysene as an isolated chemical, its occurrence with other PAH's in a wide range of occupational environments cannot be disregarded.
The following list of occupational areas, where worker exposure to chrysene and other PAH's is likely to occur, is separated into stationarypoint and non-stationary point source categories: the former refers to inplace operations, i.e., where engineering controls could be expected to substantially reduce employee exposure, and the latter refers to outdoor or mobile operations where the application of engineering controls may be more difficult.
In the latter case, however, it would be expected that natural factors (wind, etc.) would contribute to reductions in worker exposure.
While this list is based on the occurrence of chrysene as it has been reported in the scientific literature, many other occupational exposure sources undoubtedly exist.

# C. General Environment
Chrysene is found in the general environment primarily as a product of the pyrolysis of fossil fuels for energy production and the operation of diesel-and gasoline-fueled internal combustion engines.
Chrysene has been measured in the atmospheres of several major cities.
In Sydney, Australia, a 12-month survey of the ambient PAH content of suspended particulate matter showed chrysene at concentrations ranging from 0.0002 to 0.0065 (u)g/cu m of air (Cleary and Sullivan, 1965). Chrysene was found in the atmosphere of Buffalo, New York, at concentrations of 0.082-0.116 (u)g/cu m of air, and in composite samples from the air of urban Cincinnati, Ohio at concentrations of 0.0032 and 0.006 (u)g/cu m of air CCcnlee et al., 1967).
Studies have been conducted to determine the contribution of the gasoline engine to atmospheric levels of PAH's. Gasoline engine exhaust tar was found to contain 175 ppm chrysene (Hoffman and Wynder, 1962). In another investigation, the PAH emissions from diesel-and gasoline-powered vehicles were compared (Sullivan and Cleary, 1964), and chrysene was found in a diesel-trafficked area at a concentration of 0.0032 (u)g/cu m of air;
in the gasoline-trafficked area, chrysene was found at a concentration of 0.0034 (u)g/cu m of air.
In addition to the finding of chrysene in ambient air, its presence in soil and water has been substantiated. Although quantitative data are few, chrysene has been identified in soils in rural Massachusetts and Connecticut (Blumer, 1961), and in wells, rivers, lakes, and soils in Germany (Borneff, 1964;Borneff and Kunte, 1965). One investigator suggested that the occurrence of chrysene and other PAH's in rural soil is not due to fallout from polluted air but, rather, is the result of the natural pyrolytic transformation of plant organic matter to peat and lignite; or that alternatively, they occur as metabolites of organisms which reside in the soils (Blumer, 1961).
Chrysene also has been detected in certain food products: roasted coffee (Kuratsune and Hueper, 1960), spinach and tomatoes (Grimmer and Hildebrand, 1965), baker's yeast (Grimmer and Wilhelm, 1969), "liquid smoke" (Lijinsky and Shubik, 1965), smoked ham and barbecued beef (Malanoski et al., 1968), charcoal-broiled steak and chicken (Lijinsky and Ross, 1967), and electric-broiled fish (Masuda et al., 1966).
Of particular importance is the occurrence of chrysene in cigarettesmoke condensate. Chrysene has been found in cigarette-smoke condensate at a concentration of 0.06 (u)g per 100 cigarettes (Van Duuren, 1958).
Cigarette smoke may add significantly to the total exposure to chrysene from both the general environment and work environment.

# III. BIOLOGICAL EFFECTS OF EXPOSURE
A. Toxic Effects in Animals Schmid et al. (1967) used mortality and body and organ weight changes in mice as measures of chrysene toxicity. Each of 10 male AKR and 10 male C57BL/6 mice was given a single i.p. injection of 7.5 mg chrysene dissolved in 1 ml of sesame oil. All animals were alive after 20 days of observation at which time they were killed. Autopsies revealed that none of the mice had experienced any significant change in body, spleen, or thymus weight.
The investigators concluded that chrysene was not toxic as reflected by the aforementioned parameters and experimental conditions.
Gershbein (1958) tested the effects of chrysene on liver regeneration in partially hepatectomized adult male Sprague-Dawley rats. Single s.c. injections of 12.0 mg chrysene in peanut oil were given daily for the 11day test period to each rat (320 mg/kg body weight). This treatment caused no significant change in the extent of liver regeneration from that in the corresponding controls. Bernheim et al. (1953) found that a 0.3% solution of chrysene in benzene, when painted on the skins of white mice, inhibited fatty acid peroxide-induced thiobarM  -.ric acid-color development on the epidermal side, but did not in the subcutaneous fat.
The investigators attributed these results to inhibition of fatty acid oxidation. They noted that oxidized fatty acids are more effective inhibitors of certain enzymes and of bacterial growth than are the corresponding unoxidized acids, so that a carcinogen, by inhibiting peroxide formation, might produce conditions favorable for growth. They also suggested that inhibition of fatty acid oxidation may be a necessary, but certainly not a sufficient, condition for tumorigenesis.

# B. Carcinogenicity in Animals
A number of experimental animal studies of the carcinogenic potential of chrysene have yielded varying results. Most of these studies have been conducted with mice, and various investigators have described chrysene as a weak carcinogen (Wynder and Hoffman, 1959); a cancer "initiator" (Hoffman et al., 1974); an "incomplete" carcinogen (Horton and Christian, 1974); and as a cancer "inhibitor" (Huggins et al., 1964     weeks, 9 had liver tumors (1 of which was multiple) and 4 mice had lung tumors (1 of which was multiple). The investigators concluded that chrysene seemed to be a more active tumorigen than its epoxide, and that it increased the incidence of liver tumors above that in the controls, while the epoxide did not do so, and that neither chrysene nor the epoxide affected the incidence of lung tumors. The liver tumors ranged in appearance from well differentiated liver cell masses that were difficult to distinguish from normal liver tissues to those exhibiting pleomorphism, invasion, and metastasis. The increased incidence of liver tumors after exposure to chrysene, however, was not statistically significant (P=0.05).
Boyland and Sims (1967) conducted a similar experiment with chrysene and chrysene 5,6-oxide (Table II.B.). C57 black mice, 120 days old, were injected s.c. with 1.0 ml suspensions of arachis oil that contained 1.0 mg of either chrysene or chrysene 5,6-oxide, once/week, for 10 weeks. A third group, given only arachis oil, served as the control. After an observation period ranging from 60 to 80 weeks, 2 of the 20 chrysene-treated mice surviving at the time of observation of the first tumor (initial number of animals treated was not stated) had developed injection-site tumors. A comparable number of animals (3 of 20) developed injection-site tumors from the epoxide but the time-to-tumor was longer by an average of 8.6 days.
Because of the longer latency period for the epoxide, the investigators concluded that the parent PAH was a more active tumorigen. None of the control animals had tumors. Of the tumors induced by the active compounds, about 80% were spindle-cell sarcomas, about 12% were pleomorphic sarcomas and about 8% were squamous cell carcinomas.
Wynder and Hoffman (1959) applied a 1% solution of chrysene in acetone to the backs of female Swiss (Millerton) mice, three times weekly until the last animal died (sometime during the 13th month of treatment). Nine of the original 20 animals had developed papillomas and 8 had developed carcinomas, with the first tumor appearing after 8 months of treatment.
From the original data it is not possible to determine with exactitude the number of animals with both papillomas and carcinomas. A decrease in lifespan was also noted; no controls were included in the experiment. It is unlikely, however, that such a high incidence of carcinomas would occur spontaneously in this strain of mouse.
Several investigators have shown chrysene to act as a cancer "initiator." Hoffman et al. (1974) tested the tumor-initiating activity of chrysene and of six of its methyl derivatives. The purities of the test substances were greater than 99.9 %. Ten doses of 0.1 ml of acetone each containing 0.1 mg of the test PAH (total dose, 1.0 mg) were applied on alternate days to the shaved backs of each of 20 female Swiss albino mice (Ha/ICR/Mil). Application of the "promoting" substance, tetradecanoyl phorbol acetate (TPA) was begun 10 days following the last PAH-treatment.
TPA, in doses of 2.5 (u)g in 0.1 ml of acetone, was applied three times a week for 20 weeks, for total doses of 0.15 mg. Acetone alone (10 doses of 0.1 ml) served as a control treatment and was reported to have produced negative results in a separate group of mice, although no quantitative data were given.
In the chrysene-exposed group, after 20 weeks of TPA applications, 11 of the 18 surviving mice had a total of 19 tumors. The 3methyl-and especially the 5-methylchrysene were even stronger tumor initiators than was chrysene, with 14 of 20 surviving mice sharing a total of 26 tumors , and 17 of 20 surviving mice sharing a total of 96 tumors, respectively. Each compound was concurrently bioassayed for "complete" carcinogenicity in mice of the same strain and sex. Solutions of 0.1 mg of each material in 0.1 ml acetone were applied under identical conditions to the shaved backs of the animals, three times weekly for the duration of the experiment. After 30 weeks, 5-methylchrysene showed high carcinogenic activity. Each of the 20 mice had tumors (with a total of 99 tumors), including 12 with 37 carcinomas, and 2 with multiple metastases to the lungs and spleen.
Chrysene and the other five methylchrysenes showed no significant tumorigenic activity according to the investigators.
Quantitative data for chrysene and for the control vehicle were not given. Hecht et al. (1976) also tested 5-methylchrysene for "complete" carcinogenicity via two routes. Ten s.c. injections of 0.05 mg 5methylchrysene in trioctanoin (0,1 ml each injection) were given to each of 25 male C-57 black mice at 2-week intervals, after which the animals were observed for 32 weeks. This exposure to 5-methylchrysene resulted in 24 fibrosarcomas in 22 animals, with the first tumor appearing at 25 weeks.
Vehicle controls had no tumors. In addition, 5-methylchrysene was compared with benzo(a)pyrene (BaP) for tumor-initiating potential and "complete"  (1974) found that a 0.15% solution of chrysene in decahydronaphthalene (Decalin), a "non-carcinogenic" agent, when painted on the backs of 20 C3H male mice (60 (u)l doses, 2 x week), induced a papilloma in 1 of 12 surviving animals after 76 weeks of treatment (Table II.E.). However, when chrysene was applied in a 0.15% solution with a 50:50 Decalin: n-dodecane mixture (a known co-carcinogenic mixture) to the backs of 20 mice, 12 and 5 out of 19 surviving animals developed papillomas and carcinomas, respectively. The median time for tumor induction was 49 weeks.
The effects of n-dodecane alone were not tested for. The authors classified chrysene as an "incomplete" carcinogen, i.e., one lacking the co-carcinogenic activity of a strong "complete" carcinogen. Steiner and Falk (1951) studied the carcinogenic activity of chrysene in combination with 1,2-benzanthracene (Table II.F.). The actions of chrysene and of 1,2-benzanthracene were first tested separately. Fifty C57 black mice, 3-4 months old and in about equal numbers of males and females, were injected s.c. with 5.0 mg chrysene in 0.5 cc tricaprylin. There was a total of 4 injection-site sarcomas among the 24 surviving mice for a tumor incidence of 16.6 % compared with a 1.3 % incidence of tumors in the tricaprylin controls and a zero incidence in the uninjected controls. The investigators considered the results to have shown that chrysene has a definite carcinogenic potential. A tumor incidence of 18.2 % was seen after the administration of 1,2-benzanthracene with the average induction time of 285 days. A mixed solution of the two PAH's (2.5 mg each) in tricaprylin was then administered to each of 50 mice in a like manner. The tumor incidence from this dose was 44.1%. Because this incidence was a little greater than the summation of the individual responses at full doses, the investigators concluded that the results were demonstrative of either summation or synergism.
In a follow-up study by Steiner (1955) , a mixture of the "strong" carcinogen 1,2,5,6-dibenzanthrene with chrysene, when administered s.c. to approximately fifty C57BL mice, showed no significant additivity of effects, i.e., the incidence of tumors was the same as for either agent alone, and the question was raised by the investigator as to whether there had not been actual inhibition of tumorigenesis. Huggins et al. (1964) attempted to detect any inhibitory effects of chrysene upon the action of a more potent carcinogen. In these experiments, 2 mg i.v. injections of 7,12-dimethylbenz(a)anthracene (7,12-DMBA) were given to each of 74 rats on days 50, 53, and 56 of their lives.
Mammary tumors resulted in all 74 animals (100%) . A separate group of animals was given (gastric intubation) single doses of chrysene (40 mg) followed by the same 7,12-DMBA treatment. These animals showed no significant change in the incidence of mammary tumors. However, in another group of test animals, multiple doses of chrysene (15 mg x 16 days) during a period that overlapped i.v. injections of 7,12-DMBA greatly reduced the incidence of mammary tumors (60% vs 100%) . Riegel et al. (1951), painted a mixture of chrysene (15%) and methylcholanthrene (15%) in acetone on the shaved backs of CF1 mice (0.02 ml of test solution, twice weekly, for 31 weeks) and compared its carcinogenic activity with that of methylcholanthrene (15% in acetone) alone. In the group treated only with methylcholanthrene, 23 of 28 animals (82%) developed tumors after a mean latent period of 14.1 weeks.
In the group painted with the chrysene/methylcholanthrene mixture, 17 of 20 animals (85%) developed tumors after a mean latent period of 13.8 weeks.
Mean latent periods were calculated from the day that painting with the mixture was begun. From these results,, the investigators concluded that chrysene had no significant inhibitory effect on the carcinogenicity of methylcholanthrene. Similar applications of 0.20% chrysene in acetone to 20 mice resulted in one tumor among 16 survivors at 31 weeks.
In addition to the positive animal test results, indirect evidence for the carcinogenicity of chrysene can be derived from results with two different in vitro test systems. McCann et al. (1975) reported that both chrysene and chrysene-5,6-oxide were mutagenic in the Ames test. This test utilizes the organism, Salmonella typhimurium, to indicate DNA damage, and mammalian liver extracts for metabolic activation of the test chemical. Chrysene was tested on strain TA100 and resulted in 38 revertants per nanomole. The investigators noted that the relationship between the.mutagenic potency of a substance on a particular strain to its overall mutagenic potential on DNA in general, and to carcinogenic potency, remained to be determined. Huberman et al. (1972) tested the effects of chrysene (15.0 (u)g/ml for 4 hours) on Syrian hamster embryo cells in culture and found definite dose dependent increases in the numbers of "malignant" transformations in exposed cell colonies. Also, it was found that chrysene 5,6-oxide (15.0 (u)g/ml) was even more active in producing transformations. Similar relationships were observed between other PAH's and their epoxides. For this reason, and because such epoxides had been shown to be metabolic intermediates of PAH's, the investigators postulated that the epoxides are possibly the ultimate carcinogenic forms of at least those PAH's that do not contain active methyl groups.
In a follow-up to the 1972 study of Huberman et al., Huberman and Sachs (1976) tested chrysene, in the presence of enzymes required for its metabolic activation, on Chinese hamster cells in culture (2-day treatment at 1(u)g/ml/day). Chrysene showed negligible mutagenic activity (9 mutants for chrysene vs 6 mutants for solvent alone, per 10,000 surviving cells).
Negative results were also obtained by Marquardt et al. (1972) who tested the ability of chrysene and its epoxide (1.0-10.0 (u)g/ml doses for each) to transform cells derived from mouse prostate.
According to other investigators, the primary process in cancer induction (by PAH's) involves binding to a cellular component, e.g., DNA, ENA, or protein, at the K-region of the PAH (Raha et al. 1973). Typically, the K-region of a PAH is a highly reactive site.
Experimentally measured bond lengths, chemical reactivities, and valence-bond and molecular orbital calculations all agree in assigning a higher electron density to the Kregion than to any other bond in the PAH molecule (Herndon, 1973) .

# C. Toxic Effects in Humans
No reports concerning the toxicity of chrysene in humans were located.
Considerations for any toxic effects of chrysene in humans would primarily be concerned with inhalation of particulate matter, since chrysene is encountered most frequently as an airborne particulate or as an adsorbate on airborne particulates. The occurrence of any biological effect would be closely related to the physical characteristics of the particle. Particle size predominantly determines the extent to which penetration of (and retention by) the tracheobronchial tree will occur, with maximum retention falling within an aerodynamic particle size range of 0.5 to 2.0 microns (Kotin and Falk, 1964) . Ingestion and skin absorption must also be considered potential routes of exposure. Further, it should be noted that small amounts of chrysene-containing particles might be ingested following their inhalation as particles and mucus reflux from the bronchial tree (Hill et al., 1972) .
No epidemiologic studies concerning the carcinogenicity of chrysene per se were located in the literature. The carcinogenic potential of chrysene in humans must therefore be estimated on the basis of animal studies or be deduced from experiences with mixed exposure to chrysene and other PAH's.
D.

# Summary of Carcinogenicity Data
While it is clear that exposure to PAH's is associated with increased risk for both lung and skin cancer in humans, the relative contribution of Certain generalizations can be made regarding the tumorigenic potential of chrysene. For instance, its tumorigenic potential seems to vary in a dose-dependent manner. Large doses and repeated applications, as well as lengthy induction periods, are usually required to obtain significant incidences of tumorigenesis, prompting many investigators to classify chrysene as a "weak" carcinogen. Further, it seems that chrysene may have a greater effect when acting in concert with other, more potent' agents, i.e., as a tumor-initiator, a synergist, or an "incomplete" carcinogen, enhancing tumor formation but lacking the capacity for complete carcinogenesis. In one study, chrysene appeared to have inhibited the activity of a more potent carcinogen, but this case was contradicted by other similar investigations that have produced evidence to the contrary.
Thus, no generalization can be made regarding chrysene's possible tumor "inhibiting" properties. Tests on mammalian cells in culture also have produced conflicting results: some investigations have shown chrysene to produce malignant transformations in a dose-dependent fashion, while others have shown it to have a negligible effect. In microbial assays, however, chrysene has been mutagenic.
Chrysene's methyl derivatives and certain of their epoxides have been shown to possess carcinogenic potential. The 5,6 oxide of chrysene (an epoxide) was shown to be less active than chrysene in in vivo tests, but in in vitro tests on mammalian cell cultures and in microbial assays, the converse was seen. Because such epoxides have been shown to react covalently with cellular macromolecules in vitro, they have been postulated
to be likely candidates for the role of the ultimate carcinogenic derivatives of PAH's . Several possible explanations have been suggested for the lack of epoxide activity in vivo as opposed to in vitro. For instance, because of solubility and other factors the epoxide may be less able to enter the cell (Boyland and Sims, 1967), or possibly the high chemical reactivity of such epoxides could cause them to react nonspecifically in tissues (with extracellular keratin and other molecules) and hence be depleted before reaching and reacting with intracellular target macromolecules (Huberman et al., 1972). The 5methylchrysene has been shown to be both a strong, "complete" carcinogen and a more active tumor "initiator" than the parent chrysene. One possible explanation for the carcinogenic potential of this compound may lie in its metabolic activation by the formation of a carbonium ion on the methyl group (Marquardt et al., 1972).
Thus, there exists certain evidence indicating that chrysene and its derivatives have carcinogenic potential. Additional research is needed to elucidate the nature and extent of chrysene's carcinogenic activity and the mechanisms whereby such effects may be exerted.
No experimental studies were found in the literature concerning the inhalation of chrysene as an adsorbate on airborne particulate matter, i.e., the mode of entry that represents one of the most probable routes of occupational exposure.
Further, and most importantly, it should be noted that early studies which produced negative results for chrysene quite likely used inadequate numbers of animals with insufficient periods of observation (Steiner and Falk, 1951

# H. Recordkeeping and Availability of Records
Employers should keep accurate records of (1) all measurements taken to determine employee exposure to chrysene, (2) measurements demonstrating the effectiveness of mechanical ventilation, and (3) all data obtained from medical examinations which is pertinent to chrysene exposure. Pertinent records from medical examinations should be maintained for at least 30 years after the worker's employment has ended.

# V. SAMPLING AND ANALYTICAL METHODS
A workplace environmental limit for chrysene is not recommended at this time. However, in the event that NIOSH should establish such a limit (either for chrysene or for the general class of PAH's) in the future, a validated sampling and analytical procedure would be required.
NIOSH has not validated a sampling method for chrysene. Chrysene is normally encountered as an airborne pollutant (usually adsorbed on airborne particulate matter, but sometimes as a vapor) along with numerous other PAH's and their derivatives. When chrysene is encountered as a solid or is adsorbed on particulate matter, a sampling method similar to the one described in the occupational standard for coke oven emissions (29 CFR 1910.1029) would be appropriate.
NIOSH has not validated a specific analytical procedure for chrysene.
The choice of any particular method depends upon the sample source, the amount collected, time constraints, financial constraints, or personal preferences. The occupational standard for coke oven emissions (29 CFR 1910(29 CFR .1029) utilizes the benzene-soluble fraction of total particulate matter (BSFTPM) as an indicator of worker exposure to PAH's. This procedure, however, does not identify individual PAH's.
In order to identify and quantify individual PAH's, they must first be separated from any interfering compounds with which they occur.
Many reviews concerning the state of the art of PAH analysis have appeared in the literature, e.g., Sawicki, 1964;Sawicki et al., 1967;Rutzinger et al., 1973;Zander, 1975. In addition, Appendix A contains a list of some analytical methods which have been used to determine the PAH content of various compounds.