History of Offensive Odor Control
With the progress of industrial development and urbanization, complaints about environment pollution such as air pollution, noise and offensive odors increased sharply in the 1960s in Japan. To take measures against offensive odors, the “Offensive Odor Control Law” (hereafter called “the Law”), that regulates offensive odors emitted from business activities, was enacted in 1972. It could be progressive as few countries have laws applying only to offensive odors.
Various efforts toward improvement under the Law resulted in decline of complaints, with the least complaints in 1993 as shown in the figure. However, the number has been increasing dramatically since then. In 2001, there were record numbers of complaints. One of the major causes is the increase in those about service industries such as restaurants and about private households. When the law was enacted, the regulation was focused on the concentration of offensive odor substances. However, as complaints about offensive odors became more diversified, this regulation was no longer sufficient to deal with the increasing number of complaints caused by unregulated substances or complex odors. To improve these situations, the law was revised in 1995 and the odor index regulation was newly introduced, with “Triangular Odor Bag Method”, an olfactory measurement method, being officially adopted for measuring the index.
In this method, six or more members of the panel are given a set of three bags; one with a sample in it and two with odor-free and asked to choose the odorous bag. The odor is then gradually diluted and the test is continued until it becomes impossible to identify the bag with odor. The odor index is calculated by the dilution rate at which the panel can no longer tell the correct bag.
Odor Index = 10 log ( Dilution Rate )
Olfactory measurement is superior to instrumental odor measurement in its capability to deal with diverse odorants, to evaluate additive and multiplicative effects of odorants, and to meet residents’ sense of suffering from offensive odors.