Chemical compounds like polycyclic aromatic hydrocarbons (PAHs) and phthalates can affect the immune system and cause breast cancer, a researcher at the National Autonomous University of Mexico (UNAM) said Monday.

"People can develop breast cancer for genetic reasons, but this disease can also be caused by exposure to contaminants," Karen Nava Castro said in a UNAM bulletin.

Nava Castro and other UNAM researchers are trying to determine how these pollutant compounds influence the immune system independently of genetic factors.

The term PAHs refers to a class of chemicals that occur naturally in coal, crude oil and gasoline, and are produced when coal, oil, gas, wood, garbage, and tobacco are burned.

Phthalates are used in hundreds of products, including toys, vinyl flooring and wall covering, detergents, lubricants, food packaging, pharmaceuticals, and personal care products, such as nail polish, hair sprays, aftershave lotions, soaps, shampoos and perfumes.

Nava Castro said that if the immune system is impaired due to the presence of these chemical compounds, the cancer will be much more aggressive and could grow faster than if it hadn't been exposed to those pollutants.

Though the experts at UNAM say these substances modify some factors in different types of cancer, "their effects on the immune system have not yet been determined, and it's what we're beginning to study," Nava Castro said.

In Mexico, she said, little research has been done on the contamination of water, land and air, and their effects on health, "and that's the part we want to reveal so that everyone understands the risk and becomes part of the solution."