State of the Evidence 2006 Executive Summary (excerpt)

Edited by Nancy Evans, Health Science Consultant,
Breast Cancer Fund

Published by Breast Cancer Fund and Breast Cancer Action

Executive Summary
Click here to download the full report »

Breast cancer rates have been climbing steadily in the United States and other industrialized countries since the 1940s, amounting to more than one million cases per year worldwide.¹ In the United States, a woman’s lifetime risk of breast cancer has nearly tripled during the past four decades. In 2005, an estimated 211,240 U.S. women were diagnosed with invasive breast cancer and more than 58,000 women were expected to be diagnosed with one type of in situ breast cancer, meaning the tumor is confined to its original location in the breast. In 2005, breast cancer was expected to kill more than 40,000 American women² and more than 410,000 women worldwide.³ The rate of new cases per year continues to inch upward in the United States even though billions of dollars have been spent on breast cancer research.

Less than one out of every 10 cases occurs in women born with a genetic predisposition for the disease, and as many as half of all breast cancers occur in women who have no known risk factors for the disease. Recent research has made it more and more clear that breast cancer arises from a complicated mix of multiple factors, which may include inherited or acquired genetic mutations, altered gene expression and/or exposures to external agents that affect genes or the production of estrogen or other hormones. More than one exposure or event is usually required before cancer will develop, but the same set of genetic and environmental circumstances will not produce cancer in every individual.

Two decades of research on laboratory animals, wildlife and cell behavior⁴ have shown the inadequacy of the long-held belief that “the dose makes the poison.” Scientists now know that the timing, duration and pattern of exposure are at least as important as the dose. Low-dose exposure to chemicals in the environment—parts per billion or even per trillion—during a critical window of an organism’s development can cause permanent damage to organs and systems.

We are all exposed to radiation and to hundreds, if not thousands, of chemicals every day of our lives, yet we know very little about the likely synergistic effects of these multiple exposures.⁵ Testing one exposure at a time for its effects ignores this reality.

An estimated 100,000 synthetic chemicals are believed to be in use today in the United States. Another 1,000 or more are added each year.⁶ More than 90 percent have never been tested for their effects on human health.⁷ Many of these chemicals persist in the environment, accumulate in body fat and remain in breast tissue for decades. Studies by the U.S. Centers for Disease Control and Prevention (CDC) show that Americans of all ages carry a body burden of at least 148 chemicals that have been measured, some of them banned for more than two decades because of toxicity.⁸ These studies alone cannot establish cause but can reveal the internal contamination of our bodies by chemicals with known carcinogenic activity.

Patterns of breast cancer incidence indicate the importance of environmental exposures. Women who move from countries with low breast cancer rates to industrialized countries soon acquire the higher risk of their new country. The largest study ever conducted among twins found that environmental exposures unique to those with breast cancer made the most significant contribution to the development of the disease.

This State of the Evidence report demonstrates that a significant body of scientific evidence links exposure to radiation and synthetic chemicals to an increased risk of breast cancer. It summarizes the findings of more than 350 experimental, epidemiologic and ecological studies and describes some of the ongoing controversies in breast cancer research. The report recommends new directions for future research and includes a 10-point plan to act on the evidence and reduce human exposure to radiation and synthetic chemicals. This plan is based primarily on the precautionary principle, which in part states that indication of harm, not just proof of harm, is grounds for action.⁹