Improvement of interlaboratory evaluation method of olfactometry in Japan

Odor measurement is a crucial element of odor management and regulation. In Japan, nationwide interlaboratory evaluation of olfactometry using a variety of test odorants started in 2002. In the interlaboratory tests, odor index, a sensory index of odor determined by the triangular odor bag method, is measured. In 2016, interlaboratory evaluation method of olfactometry was improved. Isoamyl acetate with a concentration of 50 ppm was used as a test odor, and a total of 128 olfactometry laboratories participated in the test. In this method, test results of 11 ‘excellent qualifi ed laboratories’ designated by the Japan Association on Odor Environment (JAOE) were used to determine reference value and repeatability and reproducibility standard deviations of odor index. On the bases of these statistical values, measurement results of each laboratory were evaluated, including trueness and precision. Among 127 evaluated laboratories, 87 laboratories (68%) conformed to both trueness and precision criteria. In the case of ‘qualifi ed odor measurement laboratories’ designated by the JAOE, 53 out of 68 laboratories (78%) conformed to both criteria. The qualifi ed odor measurement laboratories registration system of the JAOE contributes to the improvement of the quality of olfactometry laboratories and the reliability of odor measurement in Japan. Improvement of interlaboratory evaluation method of olfactometry in Japan 95 Reference value and repeatability and reproducibility standard deviations were, however, not necessarily appropriate, since they were determined using odor index measurement results of regular seven laboratories that participated in the interlaboratory comparison tests in 2000 and 2001. In this study, a new interlaboratory evaluation method of olfactometry developed in 2016 is introduced and discussed. In this method, test results of ‘excellent qualifi ed laboratories’ designated by the Japan Association on Odor Environment (JAOE) were used to determine reference value and repeatability and reproducibility standard deviations. Triangular odor bag method In several countries from Europe (EN 13725 2003) to North America (ASTM E679-04 2011), including Australia and New Zealand (AS/NZS 4323.3 2001), there are standardized methods used for the dynamic olfactometry analysis. These are dynamic air dilution methods for the determination of odor concentration. On the other hand, in several Asian countries, including Japan and China, the TOBM is used for odor evaluations (Brancher et al. 2017). TOBM is a static air dilution method by which odor concentration or odor index is determined. Odor concentration is the dilution ratio when odorous air is diluted by odor-free air in an odor bag until the odor becomes unperceivable. Odor index is the logarithm of odor concentration, multiplied by ten. TOBM was fi rst developed by the Tokyo metropolitan government in 1972 (Iwasaki et al. 1972, Iwasaki et al. 1978) and notifi ed by the Japan Environment Agency in 1995 (Japan Environment Agency 1995). In the TOBM, the panel consists of six or more members who have passed the screening test using fi ve odorous compounds, i.e., β-phenylethyl alcohol, methyl cyclopentenolone, isovaleric acid, γ-undecalactone and skatole (3-methyl indole). Measurements for samples taken at odor emission sources are made in three-fold dilution descending series. Three odor bags marked with the numbers 1–3 per panel member are prepared. These odor bags are fi lled with odor-free air passed through the activated carbon column, and plugged up with silicone rubber stoppers. Odorous air is injected into one of three odor bags using a syringe until a given dilution ratio is obtained. Each member of the panel removes the stopper and sniffs three odor bags one after another by bringing the bag close to one’s nose. After sniffi ng three odor bags, each panel member chooses one bag that is likely to contain odorous air, and writes down the number of the bag chosen in a form. The responses given by the panel members are collected and compiled. The panel member who gave a correct response participates in the next session in which the sample is diluted three times further. The panel member who gave an incorrect response ends the test series. The test is continued until all the panel members give incorrect responses, in other words, it becomes impossible for all the panel members to identify the bag with odorous air. Then, odor concentration or odor index is calculated (Higuchi 2013). The difference of measurement results between the dynamic olfactometry and the TOBM were examined (Ueno and Amano 2007, Ueno et al. 2009). In the case of the measurements with the same panel members, the data obtained by the TOBM corresponded to those by the dynamic olfactometry (Yes/No mode). Naddeo et al. (2016) investigated the relationship between odor index at a municipal wastewater treatment plant determined by the TOBM and the dynamic olfactometry (Yes/No mode). The results showed a strong linear correlation between odor index determined by these two methods, especially in higher concentration range. Conventional interlaboratory