INTRODUCTION

More than 1,400 chemicals and chemical groups are known or likely carcinogens. Through industrial applications, consumer products and food, water and air, Americans are exposed daily to these cancer-causing compounds, which invade the body and build up in blood and urine. 

Federal health officials have measured many of these chemicals in our systems but the scope and range of carcinogenic pollution in people, known as body burden, has not been tallied – until now. 

Through a review of the scientific literature and publicly available human biomarker datasets, EWG compiled the first comprehensive inventory of known or likely carcinogens that have been measured in people. We found that up to 420 known or likely carcinogens have been measured in a diverse array of populations. 

Exposures to these carcinogens are by no means limited to on-the-job contact with  industrial chemicals. Data from the nationally representative National Health and Nutrition Survey, or NHANES, conducted annually by the Centers for Disease Control and Prevention, confirms that many of these carcinogens are in the bodies of Americans not at risk of occupational exposure – indeed, at any given time some people may harbor dozens or hundreds of cancer-causing chemicals. This troubling truth underscores the need for greater awareness of our everyday exposure to chemicals and how to avoid them – and beyond individual choices, the need for stronger, more effective laws and regulations. 

Carcinogens detected in biomonitoring studies come from diverse sources, including: 

• Industrial chemicals 
• Commercial products 
• Pesticides
• Heavy metals
• Byproducts of combustion, heating and disinfection
• Solvents

The mere presence of a carcinogen in the body is not necessarily a serious health threat. EWG estimated that a small subset of the chemicals inventoried for this report (nine of the more than 400 carcinogens)* were measured at levels high enough to pose non-trivial cancer risks in most Americans – risks that generally exceed EPA safety standards. NHANES has measured only a fraction of the thousands of chemical carcinogens in our lives, but it is clear that current exposures are a real risk - not only for chemicals found at levels above government standards. 

Today, scientists are looking at new ways in which chemicals likely contribute to cancer — rethinking the very notion of a chemical carcinogen. Cancer develops in stages and many carcinogens disrupt multiple or overlapping biological pathways. Scientists and physicians increasingly recognize that we need to look more expansively at the role chemicals play in cancer development. It is not enough to simply consider the effects of individual chemicals on the body. The combined effects of the many chemicals we are exposed to in real-life circumstances must also be taken into account.    

The Halifax Project,1 a consortium of hundreds of scientists and physicians from around the world, recently identified the potential for chemicals that disrupt specific biological pathways, known as the hallmarks of cancer, to form carcinogenic mixtures.2 Similarly, the World Health Organization has identified 10 key mechanisms by which carcinogens act.3 These initiatives reflect the growing recognition that many carcinogens act on multiple biologic pathways that result in the cellular changes necessary for cancer development. In addition to single chemical carcinogens in isolation, scientists are learning that the disruption of multiple pathways sufficient to cause cancer can occur via the combined effect of a mixture of chemicals. 

The array of carcinogens detected in humans is alarming. It underscores how much work is needed to reduce and eliminate toxic chemicals, particularly carcinogens, from our daily lives. Bans on chemicals such as PCBs and lead in gasoline have led to significant reductions of these chemicals – but government regulations can take decades to enact and politics can compromise their effectiveness. 

As we fight for stronger chemical laws we should also be aware of the sources of carcinogens in our environment, food and consumers products. Reducing exposures to carcinogens, whether through regulation or personal choices, can have important health benefits.

Thousands of natural and man-made chemicals are present in the environment – indoors and out, in air, food, water and consumer products. Most commercially used chemicals have never been adequately assessed for safety and most have not been biomonitored for their presence in people. Under the broken and outdated federal Toxic Substances Control Act only about 7 percent of the approximately 3,000 high volume chemicals (used in excess of a million pounds a year) have been tested for safety.  

The gold standard for assessing exposure to chemical carcinogens is biomonitoring – the measurement of chemicals or their metabolites in blood, urine, breast milk, hair or other human samples.Biomonitoring is vital for accurate determination and tracking of exposures. An inventory of carcinogens measured in people would provide a knowledge base for researchers and a tool for policy-makers and regulators to assess and reduce exposures. This is especially important in light of the conclusions of the 2008-2009 report of the President’s Cancer Panel:

The Panel was particularly concerned to find that the true burden of environmentally induced cancer has been grossly underestimated. With nearly 80,000 chemicals on the market in the United States, many of which are used by millions of Americans in their daily lives and are un- or understudied and largely unregulated, exposure to potential environmental carcinogens is widespread. . . . [T]he public remains unaware of many common environmental carcinogens. . . . Most also are unaware that children are far more vulnerable to environmental toxins and radiation than adults.4

A comprehensive review by EWG of the scientific literature revealed a stunning number of carcinogens—up to 420* – that have been detected in people through biomonitoring studies. The carcinogens detected include both natural and man-made chemicals that come from a wide range of sources, including: industrial processes, commercial products, pesticides and naturally occurring materials. Table 1 provides examples of the types of carcinogens detected and their sources (the full list of carcinogens detected in people can be found in Appendices A & B). 

Biomonitoring studies are a window into the amount of exposure, but do not address the source or route of exposure. Grouping the carcinogens detected in the human body into categories based on primary use can help us better understand these factors.

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