About off-flavors that have been occurring in the city since October 2020

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 　※As of February 5, 2024

　　　　　　　　　　　　　　　　　　　　※"119 call, etc." includes the number of cases received by the Green Environment Bureau Atmosphere and Sound Environment Division

(1) Methods of collecting and analyzing atmospheric samples

　　　　※Analysis at the General Environmental Air Measurement Bureau in the city (conducted from 2013 to 2017)

Sample sampling equipment

Tedror bag	Canister

（２） Outline of results

　①　Specimens collected on October 12, 2020

• Hydrocarbons with a carbon count of 4 to 8 carbon, such as 2-methyl pentan and n-hexane, contained in fuel evaporation gases such as gasoline, in addition to isoppentan, pentan, and butane, hydrocarbons with a carbon number of 4 to 8 in the normal atmosphere (general environment).
• In addition, ethylene and acetylene generated when burning objects are detected at higher concentrations than in the normal atmosphere (general environment), so it is presumed that the combustion of gasoline and other combustion was burned.
• Of the substances for which environmental standards have been established, "benzene" exceeded the environmental standards (annual average value of 3 μg / m3 or less), but it is a short time, it will affect health immediately. It is not considered to be affected.

　②　Specimens collected on March 4 and 6, 2021

• Propane and Butane were detected in off-odor specimens, but the results of analysis of odorless specimens and the results of the general environment conducted in the past (from January and February of FY2013 to FY2017, It was not a specific concentration compared to the average value of the analysis).
• For chemical substances with environmental standards, such as benzene and trichloroethylene, there was no detection of concentrations exceeding environmental standards.
• These results suggest that there is no immediate effect on health.

　③　Specimens collected on March 11, 2021

• Propane, butane, ethane, etc. contained in fuels such as liquefied petroleum gas (LPG), were detected at higher concentrations than odorless specimens and ordinary atmosphere (general environment).
• Substances such as pentan and isoppentan contained in the evaporation gas of gasoline and other fuels were also detected at high concentrations.
• For chemical substances with environmental standards, such as benzene and trichloroethylene, there was no detection of concentrations exceeding environmental standards.
• These results suggest that there is no immediate effect on health.

④　Specimens collected on April 30, 2021

• Propane and butane contained in fuels such as liquefied petroleum gas (LPG) were detected at higher concentrations than odorless specimens and ordinary atmosphere (general environment).
• Substances such as pentan and isoppentan contained in the evaporation gas of gasoline and other fuels were also detected at high concentrations.
• For chemical substances with environmental standards, such as benzene and trichloroethylene, there was no detection of concentrations exceeding environmental standards.
• These results suggest that there is no immediate effect on health.

⑤Specimens collected on June 28, 2021

• Propane and butane contained in fuels such as liquefied petroleum gas (LPG) were detected at higher concentrations than odorless specimens and ordinary atmosphere (general environment).
• Substances such as pentan and isoppentan contained in the evaporation gas of gasoline and other fuels were also detected at high concentrations.
• For chemical substances with environmental standards, such as benzene and trichloroethylene, there was no detection of concentrations exceeding environmental standards.
• These results suggest that there is no immediate effect on health.

⑥Specimens collected on May 17, 2022

• Freon-134a, isoptentan, pentan, butane, etc. were detected at higher concentrations than odorless specimens and normal atmosphere (general environment).
• For chemical substances with environmental standards, such as benzene and trichloroethylene, there was no detection of concentrations exceeding environmental standards.
• These results suggest that there is no immediate effect on health.

⑦About samples collected on January 19, 2024

• Propane, butane and isobutane contained in fuels such as liquefied petroleum gas (LPG) and other fuels were detected at higher concentrations than odorless specimens and ordinary atmosphere (general environment).
• Pentan contained in the evaporation gas of fuels such as gasoline was also detected at a high concentration.
• For chemical substances with environmental standards, such as benzene and trichloroethylene, there was no detection of concentrations exceeding environmental standards.
• These results suggest that there is no immediate effect on health.

（3） Sources of off-flavors
　At this time, the source is unknown.
　We will continue to respond while sharing information with related organizations in Kanagawa Prefecture and other related organizations.

Based on the Air Pollution Control Law, Motoichi has set up general environmental air measurement stations (hereinafter referred to as general stations) at 18 locations in the city to constantly monitor the status of the atmospheric environment.
In order to understand the atmospheric environment at the time of off-flavors, we analyzed items related to fuel and combustion among the measurement data (preliminary figures) of the general station in October 2020.

About constant monitoring data used for general stations and analysis (PDF: 356KB)

①　October 1, 2020 Analysis Results (PDF: 968KB)
②　October 3, 2020 Analysis Results (PDF: 978KB)　
③　October 12, 2020 Analysis Results (PDF: 1,092KB)
④　October 26, 2020 Analysis Results (PDF: 949KB)

• On each report day, the wind direction at the general station near the reporting location was in the sea to land for all four days.
• In all four days when the report was received, before and after the report time, "increase in nitrogen oxides (NOx = NOx = NOx = NO2) concentration" and "reduction of photochemical oxidant (Ox) concentration" were confirmed at the general station near the reporting place. Was. These phenomena are thought to be due to nitrogen monoxide (NO) generated by burning some substance reacts with ozone (O3), the main component of Ox in the atmosphere, to produce nitrogen dioxide (NO2), and subsequently the Ox concentration decreased. It is presumed that NO did not respond and stayed in the atmosphere.
• During the three days of reporting, except October 3, an increase in the concentration of non-methane hydrocarbons (NMHC, other than methane, non-methane hydrocarbon compounds) was confirmed at general stations near the reporting location before and after the reporting time. Isoptentan, pentan, butane and other substances detected in atmospheric samples collected at the Fire Bureau Government Building on October 12 are substances that fall under NMHC.
• The source is unknown at this stage, including whether it is one or more.

About analysis result of unpleasant odor confirmed in Fire Bureau main government building on Monday, October 12 (announced on October 13)

Information on off-flavors occurring in Kanagawa Prefecture (Kanagawa Prefecture homepage) (outside site)