The combination of chemicals interacting with us
The logical next question is: What role do the combined effects of chemicals that interfere with cancer-related processes play in the actual development of cancer?
This is especially important when you consider that many chemicals are known to accumulate and remain in the body for long periods of time. The National Biomonitoring Program, conducted through the Centers for Disease Control and Prevention, has found and measured 265 environmental chemicals in human blood and urine samples collected as part of the National Health and Nutrition Examination Survey (NHANES).4 We know that many of these chemicals will be present in the body at the same time, even if the exposures do not occur simultaneously.
Each year, NHANES evaluates about 5,000 adults and children from across the United States to assess the health and nutritional status of the nation. Biological samples taken as part of the survey provide a good “snapshot” of chemical exposures in the population. The Environmental Working Group found that 23 of the 85 “partial carcinogens” investigated by the Halifax Project have been detected in the blood and urine sampled from the NHANES population (Table 1). These 23 chemicals – mostly metals, plasticizers (BPA and phthalates) and pesticides – circulate in the body and are known to disrupt certain cancer-related pathways. EWG has independently measured many of these same chemicals in biological samples, including in umbilical cord blood, showing that exposure to these chemicals may be passed from a mother to her unborn child.5,6
Table 1. Biologically disruptive chemicals investigated by the Halifax Project that have been measured in NHANES biological samples
Alloy particles (tungsten/nickel/cobalt)*
Bisphenol A (BPA)
Dibutyl phthalate (DBP)
Diethylhexyl phthalate (DEHP)
Perfluorooctane sulfonate (PFOS)
Polybrominated diphenyl ethers (PBDEs)
* Cobalt, nickel and tungsten measured independently in NHANES biological samples.
The 23 chemicals listed in Table 1 represent only those directly measured in NHANES biological samples. There are other chemicals that are quickly eliminated from the body and unlikely to be analyzed or detected in a non-specific survey such as NHANES. Just because a chemical passes quickly through the body, however, does not mean it poses no health risk. For example, the pesticide glyphosate, recently classified as probably carcinogenic by the World Health Organization, remains in the body for only a few hours after exposure.
Chemicals can also be metabolized in the body and transformed into other substances as part of the natural process of detoxification. These metabolites are indicators that chemicals have been present and interacted with the body’s chemistry, and they, too, can be toxic. Metabolites such as atrazine mercapturate, a breakdown product of the pesticide atrazine, have been measured in biological samples but are not included in the list above.
NHANES does not provide an exhaustive list of chemicals found in the general population. EWG’s review of the scientific literature found data on 12 of the other 62 chemicals studied by the Halifax Project that have been directly measured in humans (Table 2).7-29 The Halifax Project also lists three medications – diethylstilbestrol, phenobarbital and reserpine – and melatonin, a hormone produced by the body naturally that can also be taken as a dietary supplement. The scientific data clearly shows that chemicals in the environment end up in the body and interact in ways we don’t fully understand.
Table 2. Additional biologically disruptive chemicals investigated by the Halifax Project that have been directly measured in biological samples.
Nickel derived compounds*
* Measured as nickel.