CORRELATIONS BETWEEN LUNG CANCER RATES AND QUARTZ-RICH PM10 IN IDAHO

HEALTH EFFECTS OF CRYSTALLINE SILICA IN IDAHO

NORTON, Michael R. and GUNTER, Mickey E., Dept. of Geology, University of Idaho, Moscow, ID 83844-3022, mgunter@uidaho.edu.

Quartz - the most abundant mineral in the earth's crust - has been deemed a probable human carcinogen by the International Agency for Research on Cancer, with the main threat to humans being lung cancer. In addition, EPA requires monitoring of PM10 (airborne particulates below 10 microns in diameter) because PM10 is believed to be a human health risk that leads to increased rates of respiratory diseases. Many areas in the western US, parts of Idaho included, cannot meet EPA's PM10 levels.

If exposure to high PM10 poses a health risk and, at the same time, quartz, which is a major component of PM10, is carcinogenic, then humans exposed to high levels of quartz-rich PM10 for long periods of time (e.g., farmers) may have higher rates of respiratory diseases. With this in mind, we designed a study to (1) obtain statewide PM10 data, (2) determine the mineralogy of PM10, especially quantifying its quartz content, and (3) build a database of deaths from respiratory diseases and occupations, especially lung cancer and farming, in Idaho during the past 25 years. Data on other confounders, such as smoking and age, were also obtained and factored into the study.

Quartz is a major component of PM10 (10-15%) statewide. Lung cancer death rates in Idaho are below the national average, and lung cancer death rates for farmers are no higher than for nonfarmers. There appears to be no indication that higher PM10 values cause higher incidence of lung cancer. We found no evidence, based upon a case study of the general population and the farming community, to support that living in a dusty rural area increases lung cancer rates.