Factbox: Report targets 20 possible causes of cancer

(Reuters) - The American Cancer Society, National Institute for Occupational Safety and Health or NIOSH, National Institute of Environmental Health Sciences and the National Cancer Institute named 19 chemicals and shift work on Thursday as potential causes of cancer that deserve more investigation.

They include:

* Lead, long known toxic to brain cells, also vaguely linked to cancer in people and is very common.

* Indium phosphide, used in the semiconductor industry, causes "extraordinarily high incidences" of lung cancer in rats.

* Cobalt with tungsten carbide, used to make hard metals

* Titanium dioxide - Used widely in cosmetics. There is conflicting evidence as to whether nanoparticles of titanium dioxide can pass through the skin. Rodents that inhale the compound can develop tumors.

* Welding fumes - They can include manganese and iron and studies provide some evidence that welders have higher cancer rates.

* Refractory ceramic fibers - made by melting alumina and silica. Exposure would be occupational.

* Diesel exhaust

* Carbon black - Used to make a variety of products including ink. Workers at manufacturing plants may breathe in fine particles.

* Styrene-7,8-oxide and styrene are released by burning, including cigarettes, marijuana and wood, and used to make polystyrene, copolymers and resins

* Propylene oxide - can damage DNA. Used in making plastics, workers can be exposed.

* Formaldehyde - Studies show funeral workers may have higher rates of cancer, including leukemia, and formaldehyde is very common.

* Acetaldehyde - a widely used solvent that can be breathed in and absorbed through the skin.

* Dichloromethane, methylene chloride (DCM) - a widely used solvent in paint removers, degreasers and aerosol products.

* Trichloroethylene (TCE) - another common solvent used in metal degreasing but one of the most common groundwater contaminants.

* Tetrachloroethylene (perc, tetra, PCE)- a dry cleaning chemical shown to cause cancer in rodents.

* Chloroform - found in chlorinated drinking water, ambient air, and some foods, with potential links to bladder cancer in people and mixed results in rodent studies.

* Polychlorinated biphenyls (PCBs) - once widely used and now banned, PCBs are persistent pollutants of air, water and food but studies of cancer in people are unclear.

* Di(2-ethylhexyl) phthalate (DEHP) - a very common chemical used in vinyl products and cosmetics. It can cause cancer in rats but humans may metabolize it differently.

* Atrazine - a weedkiller that may affect farmers.

* Shift work - studies show a link with breast cancer in women and also suggest exposure to light at night can disrupt natural body rhythms and cause cancer.

Source: Environmental Health Perspectives and here

(Editing by Eric Walsh)