Monitoring of occupational exposure to polycyclic aromatic hydrocarbons in a carbon-electrode manufacturing plant

.1 l,,,

Pergamon PII: s0003-4878(97)00055-0

““up.

I,?&.

Vol.

42. No

2, (2,’ 105

I II.

1998

( 1998 Brltlsh Occu~almnal Hygenc Soaety Puhhshed by Elsewer Sacnce Ltd. All rights rezerved Printed m Great Britam 0003-4878,98 $19.00+0 00

Monitoring of Occupational Exposure to Polycyclic Aromatic Hydrocarbons in a Carbon-electrode Manufacturing Plant JOOST H. M. VAN DELFT,*$ MARIE-JOSI? S. T. STEENWINKEL,* JEFF G. VAN ASTEN,” JACQUES VAN ES,? AART KRAAKS and ROBERT A. BAAN” * TN0 Nutrition and Food Research Institute, Toxicolog?) Division, Department qf’ Molecular Toxicology, P.O. Bo.u 360, 3100 AJ Zeist, The Netherlands; j-Aluminium & Chemie Rotterdam B.V., Oude Maa.sM,eg80, 3197 KJ Botlek-Rotterdam, The Netherlands; tArboNed Utrecht, P.O. Box 2400, 3500 GK Utrecht, The Netherlands An investigation is presented of occupational exposure to polycyclic aromatic hydrocarbons (PAH) in a carbon-electrode manufacturing plant, as assessed by three monitoring methods, viz. environmental monitoring of the external dose by analysis of personal air samples, biological monitoring of the internal dose by analysis of urinary 1-hydroxypyrene (I-OHpyrene), and biological effect monitoring by dosimetry of PAH-DNA adducts in blood lymphocytes. On the basis of job conditions, workers at the plant were divided into three groups with presumed low, intermediate and high exposure to air-borne PAH, respectively. All air samples showed levels of total PAH below the current MAC-value in the Netherlands, which is 200gg/m3, whereas the benzolalpyrene level was occasionally higher than the recommended concentration of 2 pg/m3. The values of 1-OHpyrene in urine from the intermediate and high exposure groups were significantly higher than those of the low exposure group, namely 3.6 and 8.2-fold, respectively. Clear external and internal exposure was thus demonstrated for workers of the high and intermediate exposure groups, but this did not result in a measurable effect at the DNA level in blood lymphocytes. Tobacco smoking, on the other hand, caused a significant increase of the levels of PAH-DNA adducts but did not affect 1-OHpyrene values. These data suggest that smoking is a more important risk factor for adverse health effects, i.e. cancer, than occupational exposure to PAH in this plant. ‘i” 1998 British Occupational Hygiene Society. Published by Elsevier Science Ltd. Ke~~rords: biological monitoring;

polycyclic aromatic hydrocarbon;

INTRODUCTION

In several industrial processes carbonaceous materials such as coke, coal tar and coal tar pitch. are produced or used. These materials all contain large quantities of polycyclic aromatic hydrocarbons (PAH). Occupational exposure of workers by inhalation of PAHboth volatile and bound to respirable particulate matter- land by dermal contact with PAH-containing materials, occurs at extensively high levels during aluminum production (including the manufacturing of carbon electrodes). coal gasification. coke

$Author to whom correspondence should be addressed, Tel: +31 30 6944438. Fax: + 31 30 6960264, e-mail: vandelft IU voeding.tno.nl Received 9 June 1997; in final form 6 October 1997.

DNA adducts; I-hydroxypyrene

production, and iron and steel founding. Many PAH have been identified as cancer-inducing chemicals for animals and/or humans (IARC, 1983). Also, there is sufficient evidence that exposures in the above-mentioned occupational settings are carcinogenic or probably carcinogenic to humans (IARC, 1984, 1987). However, it should be noted that this classification is mainly based on older studies at plants where exposure levels used to be high, and that at modern plants the exposure is considerably lower. Nevertheless, exposure to PAH still occurs and is unavoidable. In order to estimate exposure and to assess the risk of eventual adverse health effects, mainly cancer, many monitoring methods have been developed (for review see Wogan, 1992). In classical monitoring studies the exposure to agents in environmental media is 105

J. H. M. van Delft et al.

106

established, mostly in ambient air. The utility and relevance of this approach to human exposure and risk assessment have obvious limitations. External exposure analysis, also referred to as environmental monitoring, gives an indication only of the approximate dose received by an individual without regarding inter-individual differences in absorption, metabolism, bio-availability, excretion, distribution, etc. A generally more informative means of estimating an individual’s internal exposure is through biological monitoring. It comprises determination of the parent chemical-which may be representative of a mixture of chemicals-or a metabolite thereof in body fluids (blood or urine) or expired air. For PAH-exposure, I-hydroxypyrene (1 -OHpyrene), a metabolite of the non-carcinogenic PAH pyrene, is a well-validated and frequently used marker (Jongeneelen et al., 1987; van Rooij, 1994). Although biological monitoring is an improvement compared to environmental monitoring, it still has some of the above-mentioned limitations and thus may not provide the best indicator of the internally effective dose, i.e. of the actual effect at the target site for carcinogenesis. Monitoring of biological effects appears more relevant for assessment of the ultimate health risks. However, the main limitation of biological effect monitoring (BEM) is that many effects cannot be analysed directly in the target organ/tissue but are necessarily determined in surrogates that are more readily available, such as blood cells, oral mucosa cells and exfoliated urothelial cells. The biological effect markers that are most frequently investigated are biochemical markers, i.e. covalent binding products to DNA or proteins (DNA or protein adducts; dell’Omo and Lauwerys, 1993), and (cyto)genetic markers, i.e. mutations in the hprt gene, micronuclei (MN), chromosomal aberrations (CA), sister chromatid exchanges (SCE) and so-called highfrequency cells (HFC), which show a large number of SCE (Ashby and Richardson. 1985; Carano and Natarajan, 1988; Tucker and Preston, 1996). PAHDNA adducts can be determined by various methods, among which the “P-postlabelling assay is one of the most sensitive techniques (Beach and Gupta, 1992; Fennel1 et ul., 1996). In this paper the results are described of a monitoring study of occupational exposure to airborne PAH at a carbon-electrode manufacturing plant. This study was directed at the analysis of PAH in personal air samples, of urinary I-OHpyrene and of PAHDNA adducts in blood lymphocytes. MATERIALS

AND METHODS

In the investigated plant pre-baked carbon-anodes arc prepared for the aluminum production industry. The plant can roughly be divided into four sections: the carbon-anode factory, the oven sections, the anode cleaning and packing sections. and the offices and laboratory. Workers from the plant were divided into

three groups with presumed low, intermediate and high exposure to air-borne PAH, respectively, based on historic data from air sample analyses. Workers in the low exposure group were from the laboratory and office, and served as controls. The high exposure group consisted of workers from the carbon-anode factory, whereas workers who in principle were not stationed in this factory formed the group with intermediate exposure. Many of the latter were maintenance technicians active across the entire plant. At most sites of the plant a system with five shifts was used. Workers from all shifts were included in this study, except that for collection of air samples only workers from the day shifts were selected. A self-explanatory questionnaire was delivered to each participant on the day before blood collection together with distribution of the urine vessels. At collection of the blood and urine samples, the completed questionnaires were checked together with the participants. The questionnaire contained items about demography, work history, work site and job description of the last five days, unusual events at the work place, protective measures, smoking status and frequency, dietary information (consumption of alcohol, fruit, grilled meat, vitamins, etc.) and medication (past and present).

Sumple collection

Sampling of air, urine and blood was performed during the period February 12-16, 1995. For the measurement of PAH adsorbed onto airborne particulate matter in the breathing zone of the exposed workers, samples were collected with a personal air sampler. Over 68 hours, the particulates were collected on a Teflon filter (PAS 6. type FA, pore size 1.Opm; Millipore, Bedford, MA, USA). The filter was mounted in a PAS-6 sampling head (van der Wal, 1983) and a flow of 2l/min was maintained with a constant flow air pump (DuPont 2500, DuPont de Nemours and Co, Wilmington, USA). Mainly PAH with 3 or more rings, adsorbed to particulate matter, are retained on the filter, whereas the PAH in the vapour phase pass the filter. After sampling, filters were stored in the dark at - 20°C. These personal air samples were collected from 12 workers, all from the intermediate and high exposure groups. Some of these workers were monitored over several working days. Urine samples were collected during 24 hours on the fourth or fifth day of the working period. Storage In was at -20 ‘C until analysis of I-OHpyrene. addition, blood samples (20ml) were collected by venipuncture in evacuated heparin-containing tubes at the same time as the urine samples, namely at the end of the fourth or fifth day of the working period. Within 4 hours after collection lymphocytes were isolated by centrifugation of the blood on Lymphoprep (Nycomed AS. Oslo, Norway) and then stored at - 20 C until isolation of DNA.

Monitoring

of occupational

Table 1. Characteristics

exposure to polycyclic aromatic hydrocarbons

of groups under study, exposed to air-borne PAH. Low exposure

Smokers number ---median age (range) Non-smokers number median age (range) Total number median age (range)

Total PAH, median (range) Pyrene. median (range) Benzo[a]pyrene, median (range) Statistics: Mann-Whitney #number of air samples.

High exposure 9 47 (30-56)

:; (28-55)

I2 42 (35-54)

8 35 (29959)

I9 39 (28-56)

19 42 (27-54)

17 42 (29-59)

Analysis of’ DNA udducts in lymphocytes After thawing of the lymphocytes, DNA was isolated by treatment with proteinase K/sodium dodecyl sulphate and phenol/chloroform extractions (Roggeband ef (I/., 1993). PAH-DNA adducts were measured by “P-postlabelling with butanol extraction to enrich adducts (Roggeband et al., 1994). Following 2dimensional thin-layer chromatography the “P-labelled adducts were visualized and quantitated with a phosphor imager (Molecular Dynamics, Sunnyvale, CA, USA). Standard DNA samples with known amounts of benzo[a]pyrene-DNA adducts were used for calibration (Baan et al., 1997). All samples were coded and analysed in duplicate or triplicate.

-

exposure

4: (27-53)

ilnrdysis of’ I -0Hpyrene in urine The levels of 1-OHpyrene in urine were determined by HPLC with fluorescence detection using standards (Acres Chimica. Geel, Belgium) according to the method of Jongeneelen ef al. (1987). All samples were coded in order to allow blind analysis.

concentrations

Intermediate

4;: (33-56)

Anul~~sisof’PA H in nir The particulate bound PAH on the Teflon filter was extracted with petroleum ether for 15-20min. PAH levels in extracts were determined by HPLC on a reversed-phase Cl 8 column with fluorescence detection (NIOSH 5506). The EPA standard sample (Sigma, St. Louis, USA) was used for calibration. The samples were analysed for 16 different PAH, namely, acenaphtene, acenaphtylene, anthracene, benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[ghi]perylene, benzo[a]pyrene, chrysene, dibenz[a,h]anthracene, fluoranthene, fluorene, indeno( 1.2,3-cd)pyrene. naphthalene, phenanthrene and pyrene.

Table 2. Air-borne

107

Statistical analysis Statistical analysis of the data was performed with the Mann-Whitney test of the software program SOLO 4.0 (BMDP Statistical Software, Los Angeles, CA, USA). RESULTS

Study population Following the presentation of information about the study to employees of the plant, 89 of them agreed to participate by informed consent. From each exposure group 20 persons were selected on the basis of age and smoking habits, as these are generally the major confounding factors. In the end, 55 of these volunteers participated in the study, 5 dropped out because of illness or other reasons. The characteristics of the three exposure groups with respect to age and smoking habits are presented in Table 1. With respect to age all groups were comparable, although within the high exposure group there was a substantial difference in average age between the sub-groups of smokers and non-smokers. Because of the fact that some persons withdrew from the study at the last moment, the ratio smokers: non-smokers differed more than anticipated between the groups. Analysis of PA H in air Personal air samples were collected from 12 workers, 5 and 7 from the high and intermediate exposure groups, respectively. Some workers were monitored for 2-5 days during the work shift. Summarised data are presented in Table 2. Median levels of total airborne PAH in the high exposure group are 3%fold higher than those in the intermediate exposure group. In both groups a large variation was observed between

of particulate-bound

PAH, pyrene and benzo[a]pyrene

Intermediate exposure (n = 12) # 8.4 (I .8-80) 0.51 (0.104.4) 0.37 (O.OY-5.0)

test, high versus intermediate exposure

@g/m’)

High exposure (n = 18) # -____ 32 (2.33185) 2.45 (0.2846) 1.20 (0.43-3.2)

p = 0.099 p = 0.012 p = 0.024

I ox

J. H. M. van Delft Table

3. I-OHpyrene content in 24-h urine (pgjday) Intermediate exposure

Low exposure

Smokers --number ~~median (range) Non-smokers outnumber ---median (range)

cr trl.

5

7

1.9 (1.3-3.5)

IO.1 (2.4-20.2)

I4 I.5 (0.7-3.5)

4.7 (2.2-19.2)

p < 0.001

I2

High exposure 9 13.2

(10.1~45.l)/I < 0.001

8 p < 0.001

13.9 (7.7-38.8)p<

0.001

Total

number --median (range)

I9

I9

1.59 (0.66-3.54)

5.66 (2.20-20.2)

I7 p < 0.001

13.2 (7.745.1)~

< 0.001

Statistics: Mann-Whitney test, high and intermediate versus low exposure.

the various workers and the various working days (not shown). The same is observed for pyrene and benzo[a]pyrene levels, which were 4.8- and 3.2-fold increased in the high exposure group. All individual samples had levels of total PAH below the Maximally Accepted Concentration (MAC-value) in the Netherlands. which is 200 pg/m3, whereas the benzo[a]pyrene level was occasionally above the recommended exposure limit of 2 pg/m’. The benzo[a]pyrene and pyrene content of the airborne PAH samples was fairly constant within the two exposed groups and did not differ significantly between the groups (data not shown). Total PAH contained approximately 4-5% benzo[a]pyrene and 559% pyrene. This indicates that all workers in these two groups were‘exposed to generally similar mixtures of PAH, irrespective of working area or day of the shift. Analysis qf’ 1-OHpyw1c~ In all urine samples I-OHpyrene could be detected. These data are summarized in Table 3 and Fig. 1. The levels of I -0Hpyrene in urine collected from the intermediate and high exposure groups are significantly, i.e. 3.6- and 8.2-fold higher than the level of

the low exposure group, respectively. The level of the high exposure group is also significantly increased relative to that of the intermediate exposure group for total groups. Multiple regression analyses of lOHpyrene values versus hours working at the carbonanode factory prior to urine collection, showed that the best fit was for the 5-day work shift, followed by that of the last two days and the last day (correlation coefficients: 0.71, 0.68 and 0.62, respectively). All persons from the high exposure group and many from the intermediate exposure group had I-OHpyrene levels above the highest level that was detected in the low exposure group. This indicates that most persons at this carbon-electrode manufacturing plant. except those working at the office and laboratory, are exposed to levels of PAH that result in an internal exposure. Although the highest levels were observed for the workers in the high exposure group (all from the carbon-anode factory), high levels (> 10 pg/day) were also found for workers from the intermediate exposure group (5/19). Several of them (3/5) had spent 8 or more hours in the carbon-anode factory during the last 5 days, which may have resulted in the elevated levels. This indicates that in this carbon-electrode manufacturing plant the exposure to PAH is mainly

1-hydroxypyrene in urine Pg Per day 50 0 40

0

-I-0 LOW

MEDIUM

HIGH

Ic\cIs in 24-hr ur~nt’ snmples for the exposure g~mups. The levels. expressed ;I> &day, li)r the individual v orhc~-~111the low. ~ntermediatc(medium) and high exposure groups are indicated. The median in each group ih indicated I>,. ~IIC ho~~~/ont:~l lint’. I -OHp! rcnc lovely are sigilicantlq different between groups (Mann-Whltncy. ,I < 0.001 ). 1 1:. I. I-Olipyrene

Monitormg

of occupational

exposure to polycychc aromatic hydrocarbons

of PAH-DNA adducts in blood lymphocytes. The panel Fig. 2. Chromatographic pattern obtained after “P-postlabelling on the left shows a schematic diagram of the various zones and spots that have been used for quantification of the radioactivity, whereas that on the right shows adducts visualised by autoradiography.

limited to the carbon-anode factory, although it seems to occur at other sites as well.

An example of a thin-layer chromatogram with PAH-DNA adducts is shown in Fig. 2. A schematic diagram of the various zones and spots that have been used for quantification of radioactivity is depicted in Fig. 2. The clearest region in zone 2 was used to estimate background radioactivity on each chromatogram. All other quantifications were corrected for this background. The results of the DNA adduct quantifications for the three exposure groups are presented in Table 4 and in Figs 3 and 4. No statistically significant differences were observed between the groups for any of the adduct clusters. whether all adduct areas were combined or various zones and spots were taken separately. Also. no correlations were observed between I -0Hpyrene values and PAH-DNA adducts (various zones and spots), neither for all persons nor for smokers or non-smokers (data not shown). As tobacco smoking is often a major confounding Table 4. PAH-DNA

DISCUSSION

In this paper the results are presented of an investigation of occupational exposure to air-borne PAH as assessed by three monitoring techniques, namely environmental monitoring of the external dose by analysis of air samples, biological monitoring of the internal dose by analysis of urinary I -0Hpyrene. and biological effect monitoring focused on PAH-DNA adducts in blood lymphocytes. Clear external and internal exposure was demonstrated for workers of

adduct levels in lymphocytes for the exposure groups PAH-DNA

,Adduct

factor during monitoring of PAH-DNA adducts, the adduct levels between non-smokers and present smokers irrespective of their job location were compared. These data are given in Table 5 and Fig. 5. The levels of total PAH-DNA adducts in lymphocytes from smokers are higher than from non-smokers, although the difference is not statistically significant. The adduct levels in some of the zones and spots, however, are significantly higher for smokers compared to nonsmokers. This confirms that smoking is a risk factor for the induction of effects at the DNA level.

adducts per IO” nucleotides median (range)

Low exposure (17= IS)

Intermediate exposure (n = 14)

High exposure (17= 13)

650 (340-2500) 270 (130~910) 510 (290~1920) I40 (96-600) 7.2 (1.4-37) I4 (O-67) 6.8 (O-22) 0.27 (O-7.7) 4.4 (O-46) 0.6 (s-2.6)

503 (260&1500) 220 (92 620) 420 (20@ 1200) I20 (4%370) 6.9 (2.2 -28) 34 (OC140) 7.2 (O-36) 0.22 (O--9.6) 6.4 (I .416) 0.48 (c4.Y)

510 (26OGl700) I80 (92m800) 400(190~1300) I IO (70 440) 4.6 (O-39) I5 (Om94) 6.5 (2.8-84) 0 (O-6.4) 3.4 (1.1~15) 0.9 (O- 4.3)

total d1ag. /one zone I Lone 2 spot I spot _? spot :

spotJ spot i spot 6 Statistics: Mann-Whitney

test, in all cases p > 0.05.

.I. H. M. van Delft et al. PAH-ONA OddUCtS per 10e9 nut leot

totol Ides

3000

HIGH MEDIUM LOU Fig. 3. PAH-DNA adducts in blood lymphocytes of exposed and non-exposed workers. The total adduct values, expressed as adducts per IO9 normal nucleotides, for the individual workers in the low, intermediate (medium) and high exposure groups are indicated. The median in each group is indicated by the horizontal line. Adduct levels are not significantly different between groups (Mann-Whitney, p > 0.05).

the high and intermediate exposure groups, but this was not reflected in a measurable effect at the DNA level. On the other hand, tobacco smoking caused increased levels of PAH-DNA adducts but it had no effect on I-OHpyrene values. This suggeststhat smoking is a more important risk factor for adverse health effects, i.e. cancer, than the occupational exposure to PAH in this plant. Exposure to PAH in carbon-electrode manufacturing plants has been investigated previously in several other biological and/or biological effect monitoring studies. These data together with the results of the present study are summarised in Table 6. The airborne PAH levels determined in the present inves-

PAH-ONA per

tigation are of the same order of magnitude as those found in the other studies, as is also the case for the average increase of urinary I-OHpyrene concentrations over non-exposed controls. In two other studies also PAH-DNA adducts were measured, one showing no effect of exposure (0vrebo et al., 1994) and another showing an increase with increasing exposure (van Schooten et al., 1995). Other effects that have been measuredare MN, SCE and HFC (van Hummelen et al., 1993), and benzo[a]pyrene-albumin adducts in blood (Ferreira et al., 1994).The latter were clearly induced as a result of the exposure, whereas the others were not affected. In general, the urinary 1-OHpyrene concentrations

odducts d%agOnOl 10e9 nut leot rdes

zone

1000

0

800

scl

0

600

I

;j: CL

0 0

400

I 200

--8B 0

8 0

8 0 0

0 T

HIGH MEDIUM LOU t;ig. 4. PAH-DNA adducts in blood lymphocytes of exposed and non-exposed workers. The adduct values in the diagonal /one [cf. Fig. 2). expressed as adducta per IO’ normal nucleotides. for the individual workers in the low, intermediate (medium) and high exposure groups are indicated. The median in each group is indicated by the horizontal line. Adduct Icvcls are not significantly different between groups (Mann-Whttney. p B 0.05).

Monitoring

of occupational

Table 5. PAH-DNA

adduct levels in lymphocytes in relation to smoking habits PAH-DNA

Adduct

Non-smokers

tom1 diag. zone zone I zone 2 spot 1 spot 2 spot 3 spot 4 spot 5 spot 6

adducts per lo9 nucleotides median (range)

(n = 30)

Smokers (n = 12)

530(26&1700) 190 (92620) 400(19~1300) 130 (49400) 6.1 (&28) 28(&140) 6.5 (O-36) 0.1 (o-9.6) 3.6(&46) 0.5 (o-3.7)

Statistics: Mann-Whitney

test

PAH-DNA

Hemminki, 1991).In general, adducts from the overall chromatogram or from the diagonal zone are quantitated, and are used to demonstrate biological effects due to exposure to carcinogenic PAH. It has frequently been demonstrated that tobacco smoking results in increasedPAH-DNA adduct levels, total levels and those in the diagonal zone, in many tissues,such as lung, bronchus and larynx (Randerath et al., 1989), blood lymphocytes (Savela and Hemminki, 1991) oral mucosa (Stone et al., 1995) bladder (Talaska, 1991b)and urothelial cells (Talaska et al., 1991a). Furthermore, smoking increased the number of mutations in the HPRT gene (Vrieling et al., 1992),it induced the formation of SCE and DNA strand breaks in lymphocytes (Betti et al., 1995), and of haemoglobin adducts in blood (Hammond et a/., 1993), and it enhanced the concentration of 1-OHpyrene in urine (van Rooij et al., 1994). The latter effect is relatively small, as cigarette smoke contains only a small amount of pyrene compared to other PAH. We observed no significant differences in urinary I-OHpy-

adducts 10e9

per

5I a

p-value 0.14 0.004 0.022 0.060 0.001 0.055 0.42 0.59 0.010 0.047

810(340-2500) 430(130-910) 670(280-1900) 220(81-600) 22(1%39) 9.5 (048) 11 (G-84) 0 (o-7.7) 9.6 (1.7-17) 1.3 (cM.9)

are expressed as pg/g creatinine or bmol/mol creatinine. Assuming that the average concentration of creatinine in the urine is 14mmol/l (van Rooij et al., 1994)and that the urine production is about 2 1urine/ day. our 1-OHpyrene value of 1.59,ug/day for the low exposure group would correspond with 0.26 pmol/mol creatinine and 0.50 pg/g creatinine. This is in the same range as the values of negative controls in other studies. We observed that tobacco smoking increased the PAH-DNA adduct levels when specific adduct spots on the thin-layer chromatograms were evaluated, and for the adducts present in the diagonal zone, but the increase was not significant for total PAH-DNA adduct levels (Table 5). It is unknown, however, whether adducts from specific spots or zones are a better or more valid predictor of cancer risk than the overall chromatogram. Identification of the adducts would give more certainty about this, but to date this has not been achieved. Others have also described tobacco smoking-related adduct spots (Savela and

0s

III

exposure to polycyclic aromatic hydrocarbons

600

nut

dlOgOnO1 leot ides

zone

0

::

8 400

ii

4 0

8

200

f

NON-WOK

x 0

SMOKER

Fig. 5. PAH-DNA adducts in blood lymphocytes of non-smokers and smokers. The adduct values in the diagonal zone (cf. Fig. 2), expressed as adducts per 10’ normal nucleotides, for the individuals in the groups of non-smokers (non-smok) and smokers are indicated. The median in each group is indicated by the horizontal line. Adduct levels are significantly different between groups (Mann-Whitney, p = 0.004).

112

J. H. M. van Deft cf cd.

% E 2 B 1)

rene levels between smokers and non-smokers for the low exposure group or for the other two groups. The results of the DNA adduct analyses in blood lymphocytes suggest that in this plant exposure to PAH induces no measurable biological effect that may be indicative of a health risk. i.e. cancer. The question that is frequently raised is: what is the risk for adverse health effects related to an increase in PAH-DNA adducts? Up to now, this has not been answered. A comparative analysis of the epidemiological data on the influence of smoking on cancer deaths and on PAH-DNA adduct values, may yield an estimation of the relationship between DNA adduct increases and the increment of the cancer mortality risk. To calculate the cancer risk connected with increased adduct levels, we used the cigarette-smoking related mortality data from a prospective study spanning 40 years of observations (Doll et al., 1994) the longest study in this field so far published. This requires many assumptions. e.g., that dose-response relationships are linear and that all smoking-related cancers are due to PAH but not to other carcinogenic compounds in cigarette smoke. The latter assumption is a simplification but appears reasonable to a certain extent, as the main target tissue for carcinogenesis by both PAH and cigarette smoking is the lung (Ross cl crl., 1995: Doll c( (I/., 1994). The extra annual cancer mortality for subjects smoking 1524 cigarettes per day is 34001I O6persons (Doll rf ul., 1994). According to Savela and Hemminki (1991) cigarette smoking (average 19/day) results in a 2.4-fold increase in PAH-DNA adduct levels (from the diagonal zone) in lymphocytes compared to nonsmoking controls. When these data are combined. it would appear that a doubling of the PAH-DNA adduct level in lymphocytes corresponds with an extra annual cancer mortality incidence of 2400 per IO’ persons. A two-fold increase of a DNA-adduct level is an exceptionally large effect in occupational and environmental monitoring studies. Increases of DNA adduct levels in occupational and environmental settings are frequently found to be around 1.3- to 1.5fold. Even a I .3-fold increase would indicate a drastic increase in cancer mortality risk, namely 72OilO” persons/year. This increased risk is much larger than the ‘maximum permissible risk’ of 1ilO’/year (I /IO’ lifetime cancer risk) that is operational in The Netherlands in environmental policy (Health Council of The Netherlands, 1994). It is also larger than the excess cancer mortality levels of 1OO/1O”/year (4/ 1000 working life exposure) that are used to set exposure limits for occupational situations (Health Council of The Netherlands, 1995). The general conclusion from this biomonitoring study is that the occupational exposure in this plant did not give rise to a significant increase of PAHDNA adduct levels in peripheral blood lymphocytes of the workers, over the levels already present as an effect of smoking. Furthermore. the I-OHpyrene measurements in urine confirm literature data that this marker is suitable to monitor PAH exposure. that

Monitoring

of occupational

exposure to polycyclic aromatic hydrocarbons

it is insensitive to smoking as a confounding factor, and that it does not reflect total PAH-DNA adduct levels in blood lymphocytes. Acl;nol~k~~!qem~rfr.v~~Wlthout the participation of the management and the workers of the carbon-electrode manufacturing plant who volunteered to participate, this study would not have been possible. Ms. Paula van den Berg and Roos Mars-Groenendijk and Mr. Jaap Timmerman are acknowledged for their excellent skills in collection of the samples. The critical reading of the manuscript by Dr. L. Rora is highly appreciated. The work described in this study was sponsored by Aluminium and Chemie Rotterdam B.V. and the Netherlands Ministry of Social Affairs and Employment.

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