The National Toxicology Program of the US Department of Health and Human Services has added four more substances to its list of agents, substances, mixtures, and exposure circumstances that are known or reasonably anticipated to cause cancer in humans. Products containing these substances, or industries emitting them, are likely to come under more scrutiny from environmentalists and, potentially, from government regulators. The four are:

• 1-Bromopropane
• Cumene
• Pentachlorophenol and By-products of Its Synthesis
• o-Toluidine

1-Bromopropane, also called n-propyl bromide, is primarily in industrial uses such as a cleaner for optics, electronics, and metals and as a solvent for aerosol-applied adhesives, such as those used in foam cushion manufacturing. It is also used in dry cleaning and solvent sprays for aircraft maintenance, asphalt production, and synthetic fibre manufacturing.

Cumene is a natural component of coal tar and petroleum, and is found in tobacco smoke as well as the exhaust from petroleum fuelled vehicles and machinery. It is used primarily to manufacture acetone and phenol. NIEHS urges that exposure to emissions from vehicles and machinery that run on petroleum-based fuel be kept to a minimum.

Pentachlorophenol is a complex mixture of chemicals used as a wood preservative. NIEHS states that technical-grade pentachlorophenol is a mixture, which includes by-products of its synthesis, many of which are higher chlorinated dioxin compounds that may contribute to its carcinogenicity. Virtually everyone who is exposed to pentachlorophenol is exposed to its synthesis by-products. To limit exposure NIEHS recommends limiting reuse of, and contact with, pentachlorophenol-treated lumber. such as utility poles and cross arms, railroad ties, wooden pilings, fence posts, and lumber or timber for construction. Also limit contact with soil in pentachlorophenol-contaminated waste sites or around pentachlorophenol-treated lumber.

o-Toluidine is primarily used to make rubber chemicals, herbicides, dyes, and pigments. It is also used in some medical products. People can also be exposed to ortho-toluidine outside of the workplace, through tobacco smoke, the local medical anesthetic prilocaine, products that contain ortho-toluidine-based dyes, or the environment. Environmental contamination occurs when ortho-toluidine is released into air, land, or water, through its production and use.

Much more detail is available from NIEHS at http://ntp.niehs.nih.gov/pubhealth/roc/roc13/index.html