Exposure of Children to Creosote from Wood Impregnation on PlaygroundsDr. Andrea Boehncke, Dr. Inge Mangelsdorf Fraunhofer Institute for Toxicology and Aerosol Research – Drug Research and Clinical Inhalation, Working Group on Chemical Risk Assessment, Nikolai-Fuchs-Straße 1, D-30625 Hannover

Composition of creosote

– A brownish-black, viscous liquid– obtained by the fractional distillation of crude

coal tars. Coal tars are by-products in thedistillation of coal to coke or town-gas

– a complex mixture of high-boiling compounds(distillation range 200-400 °C)

– main constituents:polycylic aromatic hydrocarbons (Table 1), furthermore, phenols, creosols and xylenols

There is sufficient evidence that creosote iscarcinogenic to animals. This is due to the PAHsin the mixture (e.g. benzo(a)pyrene, dibenzo(a,h) anthracene).

Table 1: PAHs in commercial creosotes

Compound Concentration (% w/w)

Acenaphthene 3.1-14.7Anthracene 1,5-10,5Benzo(a)pyrene 0.0004-0.35Chrysene 0,3-3,5Dibenz(a,h)anthracene 0.01-0.04Fluoranthene 0,2-10,0Fluorene 3.1-10.0Naphthalene 1,3-18,0Phenanthrene 1-21.0Pyrene0.1-8.5Total PAH content up to 85 %

According to IARC (1985); ATSDR (1990); TIS (1990); Priddle & MacQuarrie (1994); Heikkilä (1987); van Rooj et al. (1993; 1998); Lehmann (1986); Sandell & Tuominen (1996)

Use of creosote

– Widely used as an impregnation agent forwood applied outdoors such as – garden fences, outdoor playing devices (e.g.

sandbox edgings), – tadpoles– railway sleepers etc.

– Mostly used in industrial applications in theso-called pressure impregnation process

– Significant amounts are applied in the privatearea creosote by brushing.

From this a potential exposure of the consumer(during impregnation) and children in contactwith creosote-treated playing devices (afterimpregnation) is to be assumed.

Suitability of benzo(a)pyrene as amarker substance

– Benzo(a)pyrene (BaP) is a marker substance innumerous studies on PAH mixtures. This holdsfor the determination of BaP in the differentenvironmental compartments and for theinvestigation of toxic and ecotoxic effects aswell.

– Question: Can BaP also be used as a marker substancefor this special exposure situation?

– Answer: Yes

– Reason: It was shown in a dermal carcinogenicity studywith mice that two samples of creosote withdiffering BaP content showed the same dose-effect relationship based on BaP. Pure BaP wasabout 5 times less effective than as a compo-nent of creosote. This is understandable con-sidering that creosote also contains other car-cinogenic PAHs apart from BaP. The carcino-genic effect of other PAH mixtures (lubrica-ting, oil, flue gas condensation products) is of a similar order of magnitude (Mangelsdorfet al., 1998).

Exposure of children to creosotefrom impregnated wood

The possible routes of exposure are given inFigure 1. The following general assumptionswere chosen. They are mainly based on the studies of Stubenrauch et al. (1995).

– regular stay on playgrounds in the age between 3 and 8 years, i.e. 6 years during alifetime

– number of stays/year: 100– exposure time/stay: 4 hours– mean body weight: 15 kg

Dermal exposure

Dermal exposure of children to creosote canoccur 1.via freshly manually impregnated wood2.via contaminated sand or soil 3.[via industrially impregnated wood due to

exudation. Old railway sleepers may containup to about 1600 mg/kg BaP (Rotard & Mai-lahn, 1987). It is not clear how much BaP can be released by exudation which dependsstrongly on weather conditions. The use of oldrailway sleepers on playgrounds is not recom-mended by e.g. the German Federal Instituteof Consumer Protection and Veterinary Medi-cine.]

1. Via freshly manually impregnated woodExudation is not to be expected with manuallyimpregnated wood as the applied quantities aresignificantly lower and complete weatheringoccurs within one to two years. The estimationsare based on the following assumptions:

– Max. BaP content of creosote: 50 ppm– Skin exposure at the workplace: 1-34 ng/kg

bw x d (derived from pyrene exposure at workplaces in the wood impregnating indus-try; van Rooij et al., 1993)

– Reduced exposure time and frequency:4 hours/day instead of 8 hours/day1 exposure event/year instead of ca. 200events/years

Result

Possible exposure via skin contact with freshlymanually impregnated wood0.003-0.09 ng BaP/kg bw x d

2. Via contaminated sand or soilSome recent literature data on the contamina-tion of sand and soil on playgrounds in the vici-nity of sandboxes are available from Denmark.The data range from < 50 mg BaP/kg dry weightto 200 µg/kg (Miljø & Energi Ministeriet, 1996).The estimations are based on the followingassumptions:

– Average BaP content of sand/soil: 60 µg/kg – Exposed body surface: 440 cm2 (inner parts of

hands)– Adhesion factor for sand/soil: 0.5-1.7 mg/cm2

(Stubenrauch et al., 1995; AGLMB, 1995)

Result

Possible exposure via skin contact with contaminated sand or soil:0.2-0.8 ng BaP/kg bw x d

FRG: 45-3490 ppm; 70%ile ≤500 ppm

NL: < 4-20 ppmSU: 300-1200 ppmPO: 300 ppmGUS:2000 ppm

Oral exposure

Indirect oral exposure due to clearance of in-haled particles is assumed to be negligible: – inhalation exposure can be shown to be very

low (see below)– BaP adsorbs especially to small particles which

have a high retention time in the lung.

However, small children in particular tend tohave a significant uptake of sand or soil duringtheir playing activities. This route of exposure isquantified with the following assumptions as abasis:

– Uptake of contaminated sand or soil: 0.5-1 g/exposure event (dependent on age; Stubenrauch et al.,1994a)

– Average BaP content of sand/soil: 60 µg/kg(see above)

Result

Possible oral exposure to contaminated sand or soil:0.5-1 ng BaP/kg bw x d

Inhalation exposure

Inhalation exposure of BaP from creosote is onlypossible by inhalation of contaminated dust.The following assumptions were compiled fromthe literature:

– Inhalation rate of children: 0.13-1.8 m3/h (Stu-benrauch et al., 1994a)

– Dust content of air on playing fields: 6.6 mg/m3 (Stubenrauch et al, 1994a)

– Dust retention in the lung: 40% (WHO, 1987)– BaP content of dust: 60 µg/kg (see above)

Result

Possible inhalation exposure to contaminateddust:0.001-0.02 ng BaP/kg bw x d

Conclusion

Most relevant exposure paths:– dermal exposure to contaminated sand or soil– oral exposure to contaminated sand or soil.

But– estimations are highly uncertain due to

numerous assumptions– the Scientific Committee of Toxicity, Ecotoxi-

city and the Environment (CSTEE) estimated a lifetime risk of ca. 10-4 for a BaP dose of 1 ng/kg bw x d (CSTEE, 1999)

– this would give clear reason for concern– especially in the context of cumulative expo-

sure (e.g. exposure via food, ambient air).

Probabilistic methods would be a helpful tool torefine the exposure assessment.

Children playing outdoors

Creosote impregnated wood

Direct contact

Skin

Volatilization

Air

Leaching

Soil, sand

Ingestion Permeation Ingestion PermeationInhalation Ingestion

References

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CSTEE (1999) Opinion (revised) on cancer risk to consu-mers from creosote containing less than 50 ppm benzo-[a]-pyrene and/or from wood treated with such creosoteand estimation of respective magnitude expressed atthe 8th CSTEE meeting, Brussels, 4th of March

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Fig. 1: Possible routes of exposure of children to creosote

Exposure scenario

Source

Release mechanism

Target

Route of exposure