As atmospheric pollution worsened, the number of patients at Nakayama Clinic in Isozu suffering from respiratory tract illnesses, such as asthma, began to increase around the summer of 1961.
In the following year, the results of a survey on diseases caused by environmental pollution conducted by the Shiohama-Rengou-Jichikai showed that 261 respondents out of a total of 2,649 (approximately 10%) suffered from asthma and other respiratory tract illnesses.