Environmental factors such as ultraviolet radiation and pollution have been known to influence the incidence rate of cancer. However, these factors do not explain the variation in incidence rates across the United States..
..Precipitation and climate zone were included in each model along with demographic variables such as annual income, population by gender, race, and age—important control variables. Results indicate that in the United States, counties with high precipitation and cold climate have statistically significantly higher rates of invasive cancer incidence rates (p < 0.05). This is the first study reporting precipitation and climate as natural environmental factors responsible for the geographical disparity in invasive cancer incidence rates within the United States.