In the Japanese Pollutant Release and Transfer Register（PRTR）framework, which is a chemical substance management system, small-scale business operators who employ less than 21 employees are not required to report the amount of any released chemicals. This paper proposes a method to estimate the distribution of the number of small-scale business operators by industry and another method to estimate the amount of chemicals released from their corresponding operations. By combining the relevant data, the distribution of emissions from small-scale businesses was estimated in an area with a cluster of small-scale business establishments in the Osaka Prefecture and visualized through geographic information system mapping. Depending on the chemical substance and industry, the estimated distribution of the released chemicals was different from that in the PRTR. This finding suggested that the reported release in PRTR is not sufficient in assessing the risk of chemical leakage during a natural disaster.