Soils selenium level and esophageal cancer: an ecological study in a high risk area for esophageal cancer.

PROJECT Golestan province, located in northeast of Iran, has been known as a high risk area for esophageal cancer (EC). This study was conducted to assess the relationship between soils selenium (Se) level and development of EC in this region. PROCEDURES In this ecological study, 135 blocks were identified in Golestan province based on geographical altitude and longitude on the map. One soil sample was collected from the center of each block. Then we investigated Se concentration in soil samples by flame atomic absorption spectrometry. Statistical analysis was performed by the Pearson correlation test and Student t-tests. P-values of less than 0.05 were considered as significant. RESULTS The mean+/-SD of soils Se level in Golestan province was 3.7+/-1.61 mg/kg. There was a positive correlation between soils Se level and EC rates in this area (P=0.03) (Pearson correlation coefficient=0.19). Soils Se concentration was significantly higher in high (4.13 mg/kg) than in the low (3.39 mg/kg) EC rate areas (P=0.01). CONCLUSIONS We found high soils Se concentration and a significant positive relationship between soils Se level and EC rate in Golestan province of Iran. So, high soils Se level may play a possible role in developing EC in this area, specifically in Turkmensahra (very high EC rates).