Wood preservatives protect outdoor timber from rot, fungi, and insects. The two most historically significant are creosote (a coal tar distillate containing hundreds of PAH compounds including benzo[a]pyrene) and chromated copper arsenate (CCA, containing arsenic, chromium, and copper). Both are classified as carcinogens and have been restricted for domestic use in the EU and UK, though legacy-treated wood remains in many gardens. Modern replacement preservatives including copper azole and IPBC-based products raise their own emerging concerns.
Where it's found
Garden railway sleepers and ornamental timber treated with creosote. Older fence posts, telegraph poles, and agricultural buildings treated with creosote — particularly pre-2003 installation. Decking, fence posts, children's play equipment, and garden furniture treated with CCA before 2004 restrictions. Pallet wood, which may have been treated with a variety of preservatives (some pallets use methyl bromide or other fumigants). Treated wood leaches preservative chemicals into soil and is absorbed by root vegetables grown in adjacent beds. Surface contact with creosote-treated wood leaves dark oily residue on skin.
Routes of exposure
Dermal contact with treated wood surfaces is the primary route for both creosote and CCA — children playing on or around treated garden timber, decking, or play equipment absorb chemicals through skin contact and hand-to-mouth behaviour. Ingestion of soil contaminated by leachate from CCA-treated wood (particularly relevant for children playing in gardens with treated play equipment or decking). Inhalation of vapours from freshly cut or heated creosote-treated wood. Dietary uptake by root vegetables grown in beds adjacent to CCA-treated timber raised beds. Occupational exposure for timber treatment workers and those cutting or treating wood.
Health concerns
Creosote contains hundreds of PAH compounds including confirmed carcinogens (benzo[a]pyrene is IARC Group 1). Occupational creosote exposure is classified IARC Group 1 for skin cancer and scrotal cancer. Creosote is also a powerful skin sensitiser and photosensitiser causing severe dermatitis on sun-exposed skin. CCA contains inorganic arsenic (IARC Group 1, causing bladder, lung, and skin cancer), hexavalent chromium (Cr VI, IARC Group 1, causing lung cancer), and copper (an essential nutrient at low levels but toxic at high levels). Arsenic from CCA leaches into soil and can be absorbed by plants and ingested by children touching treated surfaces. Children playing on CCA-treated wood have measurably higher urinary arsenic levels.
Evidence
Creosote PAH carcinogenicity from occupational studies is IARC Group 1. CCA arsenic and chromium (VI) carcinogenicity is IARC Group 1. The specific concern for children around CCA play equipment has been well characterised in studies measuring urinary arsenic in children using treated versus untreated playground equipment. The EU and UK restrictions on domestic use followed these evidence-based risk assessments.
Who's most at risk
Children who play on or around CCA-treated decking, play equipment, or garden railway sleepers are particularly at risk through dermal contact and soil ingestion. Children playing on soil adjacent to CCA-treated raised bed borders may absorb arsenic that has leached into the soil. Occupational timber treatment workers face the highest direct chemical exposures.
Regulatory status
RegulationCreosote for amateur/non-professional use has been banned in the EU and UK since 2003 (Biocidal Products Regulation). CCA-treated wood for domestic applications (decking, play equipment, garden furniture, fencing that people may touch) was restricted in the EU from 2004. Both remain permitted for professional/industrial uses (railway sleepers, telegraph poles, heavy civil engineering timber) with controls. Modern water-based copper azole preservatives are the primary current replacement for domestic timber treatment.
How to reduce your exposure
Do not use creosote or CCA-treated timber for raised vegetable beds, play areas, or areas where children will have regular skin contact. If you have existing CCA-treated decking or play equipment, consider sealing with a protective paint or oil coating to reduce arsenic leaching, or plan to replace. Wash children's hands after playing near older treated timber. Do not burn CCA-treated wood — this releases arsenic and chromium VI in smoke and ash. For DIY timber treatment, choose water-based modern preservatives compliant with current biocide regulations. Railway sleepers sold for garden use may be treated — check treatment type before use near food growing areas.
The nutrition connection
Growing vegetables in raised beds is a wonderful way to improve diet quality and food security — but the material used to construct those beds matters significantly. CCA-treated timber, old railway sleepers containing creosote, and some treated pallet wood can contaminate the very vegetables intended to improve health. Building raised beds from untreated hardwood (oak, larch), naturally rot-resistant species, or certified safe alternatives ensures that the nutritional benefits of home-grown vegetables are not offset by chemical contamination from the infrastructure used to grow them. This is a clear, practical Nutriofia message: grow your own vegetables, but in materials that are safe.