County-Level Cumulative Environmental Quality Associated with Cancer Incidence

Authors: Jagai, JS et. al.

Source: Cancer doi: 10.1002/cncr.30709

www.onlinelibrary.wiley.com/doi/10.1002/cncr.30709/abstract

Cancer in the US is a public health problem. Analysis of twins has shown that genetics are the cause of about 50% of cancer cases, suggesting that the environment plays a significant role in the development of cancer in this nation. It is well known that environmental exposure consists of many factors, and these factors often interact to produce specific effects.

The Environmental Quality Index (EQI) is a measure of environmental exposures in the US from 2000-2005. The EQI places all environmental sources into five categories: air (including the presence of pollutants), water (including drinking water quality, recreational water quality, chemical contamination and drought), land (including use of agricultural pesticides and radon), buildings (such as roads, public transit use and the presence of subsidized housing) and sociodemographics.

The investigators collected the rates of cancer incidence across the US from 2006-2010, expecting that there would be a lag time between environmental exposure (EQI) and the development of cancer. Cancer rates from over 85% of the nation’s counties were collected.

The overall cancer incidence was strongly associated with poor overall environmental quality, although there was some variability in thinly and densely populated areas. Specifically, air, building and sociodemographic factors were linked to the incidence of cancer. The incidence of breast cancer in the US followed these trends, and appeared most influenced by air environmental factors.

This study supports the understanding that there are multiple factors in the environment that combine to influence the development of cancer in the US.  Breast cancer is no exception. While studying the effects of specific environmental exposures and breast cancer is helpful in understanding the disease, studying the cumulative effects of multiple exposures allows a better clarification of their impact.