In these ZIP Codes, it was anticipated that very few people would get cancer. One or two more people with cancer in these ZIP Codes would cause them to be high compared to the entire State. Looked at over time, the cancer incidence in these ZIP Codes might be very different, as more people or fewer people are diagnosed with cancer. We don t know. Unfortunately, making a map showing excess cancer incidence can t tell us the reason for the increase.
Cancer develops slowly in people.
It usually appears many years after exposure to a cancer causing agent. This is called the latency period. Latency is one of the reasons it is difficult to determine what causes cancer in humans. Also, many people move several times during their life making it difficult to link exposures to cancer causing agents to where a person currently lives. If you live or lived in a ZIP Code that is shaded purple or marked with lines, it does not mean that living in this ZIP Code makes you more likely to get cancer than someone who lives in a ZIP Code that is shaded green or gray.