Overview:

Breast cancer rates vary across California, with some areas having significantly higher rates than others. Many factors can contribute to this variability; differential exposure to environmental contaminants, e.g., via drinking water supplies, is one possible causative factor.

Carcinogens may be added to household water supplies in four main ways. They can be: (i) present in the source water prior to any human inputs, (ii) contributed by regional or local land uses such as transportation, energy production or agriculture, (iii) added (or removed) by water system treatment design and operation choices such as disinfection (which can form byproducts), membrane filtration (which can remove many substances) or leaching from materials used in the community water distribution system, or (iv) contributed by household-level factors like distance from the treatment plant (which impacts concentrations of disinfection byproducts) or household plumbing materials, It is important to the breast cancer community to understand the identities and the sources of any unregulated chemicals present in drinking water that may contribute to differential rates of the disease across California.

Californians are continuously exposed to a wide variety of structurally diverse chemicals from many sources, including environmental and food contaminants, therapeutic agents, chemicals from commercial and consumer products, personal care products and many other sources.

Known mammary gland carcinogens come from a broad array of chemical classes (e.g., dioxins, polychlorinated biphenyls (PCBs), phenols like bisphenol A (BPA), phthalates, polyfluorinated alkyl substances (PFAS), halogenated flame retardants and solvents, pesticides, drinking water disinfectant by-products, pharmaceuticals, hormones, natural products, and dyes); many representatives of these broad chemical classes are not routinely monitored in water supplies. Compounds in many of these chemical classes have also been identified as endocrine disruptors, which can produce a diverse spectrum of adverse health effects including enhancing the development and progression of breast cancer.

Since most breast cancers are estrogen-dependent, increased growth and proliferation of breast cancer can be stimulated by chemicals that can directly activate and/or enhance the activity of estrogen receptors (ERs). Many estrogenic endocrine disrupting chemicals (EDCs) have been identified in recent years, and it has been suggested that the increased incidence of breast cancer in industrialized countries is linked to such chemicals. Given the well- documented and widespread presence of estrogenic chemicals in surface waters and their potential to end up in drinking water, the detection, identification and characterization of estrogenic chemicals is of major importance.

Advances in the accuracy and resolution of mass spectrometry have spurred rapid developments in “nontarget analysis” in which a much broader array of potentially estrogenic chemicals can be monitored compared with traditional, targeted approaches. These developments have allowed the detection of previously unsuspected industrial chemicals and chemical transformation products in the Rhine River, novel PFAS in the Tennessee River, and environmental transformation products in the San Francisco Bay Delta. Application of these techniques to drinking water has led to discovery of novel disinfection byproducts and other potentially toxic organic compounds. Systematic application of these novel techniques to California drinking water supplies has the potential to fill important knowledge gaps regarding environmental contributors to breast cancer development.

In this project, tap water was collected twice from 120 California households receiving their water from one of 8 public suppliers. Bottled water (15 brands, two times each) were tested using identical approaches for comparison. Half of the household water systems tested were located in areas of concern for elevated breast cancer rates. Water samples were also tested to determine whether they contained compounds that might interfere with the endocrine system, one potential pathway to breast cancer.

Research questions:

1. Which water sources are associated with the highest levels of endocrine disrupting compounds or known cancer causing agents? Are these water sources in communities with historically elevated breast cancer rates compared with areas with lower rates? How do these compounds vary across households within a particular water system?

2. How do water treatment processes, particularly disinfection and advanced treatment operations influence the levels and identities of estrogen active or carcinogenic compounds present in water supplies?