Iodine in the urban air was determined and it was found that the iodine was contained in the suspended particles. In addition, lead and copper were also determined in the same samples. From the correlation between the iodine and lead and copper concentrations and the fact that the lead in air is originated from the combustion of the fossil materials, the iodine was also appeared to be generated from the combustion of those materials. By the results of our experiments, the average value of iodine concentration in air at ground level in Tokyo was 7.8μg/1, 000m3, and the average values of lead and copper were 60μg/1, 000m3 and 59μg/1, 000m3, respectively.