Side effects of<unk>  products include skin irritation, sun sensitivity, allergic reactions, and skin discoloration. It is unclear if use during pregnancy is safe for the baby and use during breastfeeding is not typically recommended. According to the National Psoriasis Foundation,<unk>  is a valuable, safe and inexpensive treatment option for millions of people with psoriasis and other scalp or skin conditions. According to the FDA,<unk>  concentrations between 0.5% and 5% are considered safe and effective for psoriasis. Cancer Long-term, consistent exposure to<unk>  likely increases the risk of non-melanoma skin cancers. Evidence is inconclusive whether medical<unk> , which does not remain on the skin for the long periods seen in occupational exposure, causes cancer, because there is insufficient data to make a judgment. While<unk>  consistently causes cancer in cohorts of workers with chronic occupational exposure, animal models, and mechanistic studies, the data on short-term use as medicine in humans has so far failed to show any consistently significant increase in rates of cancer.<unk>  contains many polycyclic aromatic hydrocarbons, and it is believed that their metabolites bind to DNA, damaging it. The PAHs found in<unk>  and air pollution induce immunosenescence and cytotoxicity in epidermal cells. It's possible that the skin can repair itself from this damage after short-term exposure to PAHs but not after long-term exposure. Long-term skin exposure to these compounds can produce "tar warts", which can progress to squamous cell carcinoma.<unk>  was one of the first chemical substances proven to cause cancer from occupational exposure, during research in 1775 on the cause of chimney sweeps' carcinoma. Modern studies have shown that working with<unk>  pitch, such as during the paving of roads or when working on roofs, increases the risk of cancer. The International Agency for Research on Cancer lists<unk> s as Group 1 carcinogens, meaning they directly cause cancer. The U.S. Department of Health and Human Services lists<unk> s as known human carcinogens. In response to public health concerns regarding the carcinogenicity of PAHs some municipalities, such as the city of Milwaukee, have banned the use of common<unk> -based road and driveway sealants citing concerns of elevated PAH content in groundwater. Other<unk>  causes increased sensitivity to sunlight, so skin treated with topical<unk>  preparations should be protected from sunlight. The residue from the distillation of high-temperature<unk> , primarily a complex mixture of three or more membered condensed ring aromatic hydrocarbons, was listed on 13 January 2010 as a substance of very high concern by the European Chemicals Agency.
Coal tar
Asbestos
Khat
Polychlorinated naphthalene
Vinyl chloride
Dissolvable tobacco
Triphenylchloroethylene
Benzene