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Systematic Analysis of Environmental Release Process andEmergency Response in Chemical Accident
Yosuke KOYAMA*, Yoshitaka IMAIZUMI and Noriyuki SUZUKI
Center for Health and Environmental Risk Research, National Institute for Environmental Studies
16-2 Onogawa, Tsukuba-shi, Ibaraki, 305-8506, Japan*E-mail: koyama.yosuke@nies.go.jp

Abstract
Various harmful substances have been released into the environment due to increased occurrences ofchemical accidents. However, only a limited number of the cases have been analyzed from the perspective of
health and environmental risks to the general environment. In this study, we conducted questionnaire andinterview surveys with site operators to collect information related to substance release processes andresponses to them in past accidents. In addition, we extracted factors relevant to the emergency responses tothe accidents and systematically analyzed the release processes.
Key words :	accidental release, case analysis, chemical substances, emergency response

1. Introduction

2. Methods

Various harmful substances have been released into
the environment during chemical accidents such as fires,
explosions and spills. The number of accidents at
facilities handling hazardous materials has been
increasing since the 1990s (Fire and Disaster
Management Agency, 2016). Quick and appropriate
responses to accidental releases are essential forminimizing health and environmental risks. It is not easy
to obtain information on risk assessment due to thedifficulty of identifying substances and fluctuations in theamounts released and concentrations in the environment.
Therefore, only a limited number of cases have been
analyzed from the perspective of risks to the generalenvironment despite the many accidents that haveoccurred. Systematizing the behaviors of released
substances and accident patterns is important for ensuring
quick and appropriate responses to accidents.
In this study, we have systematically analyzed theprocesses of chemical releases and responses of facilities
and government bodies to accidents based onquestionnaire and interview surveys. The questionnaires
were designed to collect a variety of information related
to release processes and responses in past accidents. Theinterview surveys were conducted to obtain detailed
information on situations and personal opinions whichwere hard to obtain from the questionnaire. In addition,
we paid attention to practical information that had been
useful in responses soon after accidents based on thesurvey results.

2.1 Questionnaire Survey on Chemical Accidents
For the purpose of collecting information as a basis
for categorizing chemical accidents, we conductedquestionnaire surveys and interview surveys with site
operators about accidents that had occurred in thepast. To list up target accidents for these surveys,
past accidents in Japan that may have involved
releases of chemical substances were extracted fromthe Database of Disasters and Accidents (Accident
and Disaster Information Center (ADIC)). Thesesurveys were carried out twice. The first (Survey 1)
was conducted in April 2019 and the second (Survey 2)
was conducted in April 2020. Survey 1 covered
accidents that had occurred in recent years (2017 to2019) with no limit on the type of industry, andthe Survey 2 covered accidents that had occurred
at industrial sites involved in “manufacture of chemical
and allied products” after 1990 except for casesthat would duplicate those in Survey 1. Survey 2 wasintended to collect more information about thechemicals released. The number of questionnaires
distributed in Survey 1 was 100, and in Survey 2, 51. In
both surveys, the interviews were conducted after
the questionnaire survey (Survey 1: 20 interviews, Survey
2: 18 interviews).
The questions asked in the questionnaire surveys
were mainly concerned with the handling of substances at
the time of the accident, the state of the released
substances in the environment and the emergency

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24/2020: 261-266
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Table 1 Questions asked in the questionnaire (outline).
No.

Questions

Q1

Were there any investigations or guidance given by administrative authorities after the accident?

Q2

Was a report on the accident prepared by the operator or the administrative authorities?

Q3

Can the report in Q2 be provided?

Q4

What was the cause of the accident?

Q5

Please list substances handled that were related to the accident.

Q6

How much of the substances handled was stored?

Q7

What purposes do the substances handled have in the processes at the site? (e.g., raw materials, by-products, waste products)

Q8

Please list any chemicals that were thought to be unintentionally produced by the accident, if any.

Q9What is the reason that you judge the unintentionally produced chemicals to have been produced?

Q10

For how long were the substances released after the accident?

Q11

Were any substances released into the general environment during the accident?

Q12

Regarding Q11, what and how much of the substances were released into the general environment?

Q13

Were any concentration measurements performed in the general environment after the accident?

Q14

Regarding Q13, please give the name and concentration of the substance.

Q15

Please describe the time-series transition of events from the occurrence of the accident to the convergence.

Q16

Is it possible for you to cooperate with an interview survey?

responses to the accident. Table 1 outlines the questions.

3. Results and Discussions

2.2 Considering Practical Information in Emergency
Responses
Based on the results of the surveys in Section 2.1,
information desirable to obtain for emergency responses
was examined. Methods of identifying released chemicals,considered to be a particularly important factor in
conducting environmental surveys, were compared. Here,the advantages and disadvantages of interviews with site
operators and utilization of the Pollutant Release
and Transfer Register (PRTR) notification data werecompared. In addition, examples of other factors andcriteria that could characterize chemical accidents wereidentified.

3.1 Analysis of Questionnaire Replies
Table 2 shows the number of replies to thequestionnaire survey by industry. In Survey 1, as forclassification of industry, “manufacturers of chemical andallied products” (7 respondents) accounted for the highest
number of respondents. Next were “manufacturers of
petroleum and coal products” (4 respondents), “manufacturersof transportation equipment” (4 respondents), and “waste
disposal businesses” (4 respondents). They accounted forabout 70% of the total respondents (19 of 29 respondents).
In Survey 1, accidental fires (including explosions)accounted for the majority of cases (27/29). On the other
hand, in Survey 2, accidental fires comprised less than
30% (9/34 cases). In many of the cases investigated inthis study, especially regarding accidental fires, thereports on the accidents were prepared by the operator or
administrative authorities (obtained from Q2 in Survey
1). There were few cases, however, from which
information on releases to the general environment could
be obtained, because most of the reports were on
investigations into causes and suggestions for
improvement of facilities and operations.
Regarding whether chemical substances had beenreleased into the general environment or not (Q11), in
Survey 1, seven respondents replied “They were released
to the general environment,” and about 30% (10respondents) replied that it could not be ascertained(“Unknown” or no reply). In Survey 2, about 40% (13/34
respondents) replied “They were released to the generalenvironment,” while all other respondents replied “Thereleased substances remained within site boundaries.”
Regarding the handling substances related to theaccident (Q12), relatively detailed information was

2.3 Classification of Release Processes and Responses
To manage the risks to the general environment from
accidental releases of chemical substances from industrialsites, it is important to analyze systematically the
behaviors of substances in the environment from the timeof release of the chemical substances to the time of
exposure. The concept of a migration process of released
substances in environmental media had been brought up
in several studies (International Atomic Energy Agency(IAEA), 2002; Moriguchi, 2013; World HealthOrganization, 2009), but there were differences in thesettings of the environmental media. In this study, for the
purpose of covering various possible situations, attempts
were made to classify the migration processes ofsubstances in the environment and the corresponding
emergency responses. Possible emergency responses
were listed in consideration of both possible general
responses and replies to the questionnaire survey.

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263

Table 2 Number of replies to the questionnaires.
Survey1

2Year

2017–20191990–2016

Industrial classification*
Code

Name

Number of
replies

16

Manufacture of chemicals and allied products

7

17

Manufacture of petroleum and coal products

4

18

Manufacture of plastic products, except as otherwise classified

3

21

Manufacture of ceramic, stone and clay products

224

Manufacture of fabricated metal products

1

25

Manufacture of general-purpose machinery

1

27

Manufacture of business-oriented machinery

1

29

Manufacture of electrical machinery, equipment and supplies

1

31

Manufacture of transportation equipment

4

55

Miscellaneous wholesale trade1

88

Waste disposal business

4

16**

Manufacture of chemical and allied products32*
The industrial classification (code and name) shown in this table are based on Japan Standard Industrial Classification(Ministry of Internal Affairs and Communications, 2013).
** In Survey 2, a four-digit industrial classification was used, but here they are indicated as the main group by the first two digits.

obtained for leakage accidents from “manufacturers ofchemical and allied products,” but from the others, there
were few cases in which details on those substances could
be identified. This was because the causal substances in
the accidents were often uncertain in the cases of fires or
explosions.
Regarding release duration (Q10), in Survey 1,
excluding “unknown” cases (9 cases), five cases were“instantaneous releases due to explosions” and 11 cases
were “1 to 6 hours,” indicating the time it took to
extinguish the accidental fires. In Survey 2 where manycases were leakage accidents, many (23 cases) replied“within an hour” (of which one was an instantaneous
release), while in one case, it was estimated that leakage
due to corrosion of buried piping had continued forseveral months.
Regarding unintentional reaction products (Q8), in
both surveys, about half replied “There was no possibilityof producing them.” In Survey 1, “Unknown” accounted
for about 25% (7/29 cases), while in Survey 2,“Unknown” accounted for only two cases and more than
40% (14/34 cases) replied “There was a possibility of
producing them” (due to combustion or unintended
chemical reactions). Since Survey 2 covered accidents inchemical plants, it was thought they had knowledge ofthe substances being handled and reaction products in theaccident. Generally, it is thought that unintentional
reaction products are generated in accidental fires. In
these surveys as well, many of the replies regarding
accidental fires were “There was a possibility of
producing them.” Therefore, understanding ofunintentional reaction products in accidental fires isthought to be important.
Regarding measuring concentrations in the generalenvironment (Q13), in both surveys, approximately 25%(Survey 1: 7/29 respondents, Survey 2: 8/23 respondents)
replied that it had been conducted in some way after theaccident. However, most of these were not conducted by
the emergency response, but referred to data obtained byconstant monitoring at site boundaries or periodic surveysof the surrounding environment. Estimations ofenvironmental concentrations (model calculations, etc.)
had been performed in only two cases in Survey 2.
The results of the questionnaire survey clarified that
there were few cases of emergency response that involved
environmental monitoring for the general environment.
In the interview survey, some site operators said that the
emergency responses at the time of the accident had been
multiple and complicated, and environmental monitoring
was not given very high priority.
3.2 Practical Information for Emergency Responses
The results of questionnaire survey in this study
revealed that information on chemical substances releasedin the course of accidents was unavailable in many cases.
Therefore, it is important to establish methods for
identifying the chemical substances released into thegeneral environment. The methods currently available toidentify released substances are summarized below, alongwith their advantages and disadvantages.
As to methods of identifying released chemical
substances, it is conceivable not only to ask the site
operators, but also to use the related notification data on
annual emissions or amounts handled.
Interviews with the site operators may provide a
possible way to obtain information useful for risk
assessment such as on substances handled during theaccident, amounts released and so on. However, it islikely that they will not be able to reply immediately after
the accident. In addition, even if it is possible, it will takesome time to conduct. Therefore, this is not a realistic
approach, especially in the case of emergencies.
PRTR notification data in Japan (Ministry of
Economy, Trade and Industry, published annually) is

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Y. KOYAMA et al.

readily available. PRTR data cover 462 substances withrelatively high environmental risks and provide locationsof business sites where they may be released ortransferred at normal times. However, an analysis ofSurvey 1 (Koyama et al., 2019) revealed that only in a
few cases were PRTR substances reported by the site
operator related to the substances released during theaccident. (In Survey 2, many cases had occurred before
the start of the PRTR system, so a sufficient comparison
could not be made.) Therefore, it can be said that PRTR
data cannot always be used effectively regarding
emergency responses.
None of the methods shown here is sufficient, so it is
not easy to quickly identify a target substance using asingle method. To carry out an appropriate environmental
survey, the best way at present to estimate the substancesthat may have been released is by using a combination ofthese methods. Therefore, it is important to collect andanalyze relevant information from before the accident sothat the necessary information can be quickly obtained infuture accidents or disasters.
There are thought to be some key factors defining
the characteristics of chemical accidents, although not all
relevant information could be obtained due to lack of
information from the questionnaire surveys. These factors
may be divided into those related to characteristics ofchemicals (e.g., visibility, specific gravity, solubility,
toxicity) and those related to characteristics of accidents(e.g., release destination, duration, quantity, types ofsurrounding areas).
It is important to set criteria for such factors toenable quick and appropriate responses. As an example ofAccident site

ReleaseAtmosphere

3.3 S
 ystematic Classification of Environmental Release
Processes and Responses
To systematically classify the processes of release ofchemical substances, the migration of chemical
substances between media is expressed as a matrix in
Fig. 1 referring to the migration matrix of radioactive
materials (IAEA, 2002). In addition, the possible
responses to this are summarized in Table 3 and Fig. 2.
Here, responses are classified into two categories,“Identification” and “Management.” In addition, theresponses are separated into what is done for the media
and what is done for transfers between the media.
Regarding responses for the media, examples of“Identification” responses were “visible observation(smoke, crop damage, etc.),” “atmospheric monitoring”
and “atmospheric concentration model calculation,”while an example of a “Management” response was

ReleaseDry and wet
deposition

Volatilization

Rivers, lakes

Re-suspension

Translocation

Re-suspension

Translocation

Re-suspension

Translocation

Volatilization

criteria for toxicity, there are five levels (A to E) of
classification based on the toxicity categories of the GHS
classification system (Osaka Prefectural Government,2014). This classification is useful in that it can beapplied to various chemical substances. For substanceswith high acute toxicity, it may be possible to use criteria
for emergency responses such as Acute Exposure
Guideline Levels (US Environmental Protection Agency).
As a next step, through a detailed study of thesefactors and criteria, it may be possible to classify
chemical accidents with similar features. In the future,reviewing and classifying the responses actually taken or
to be taken in similar cases will make these factors more
useful in responses to future accidents.

ReleaseDry and wet
deposition

Dry and wet
deposition

Translocation

Translocation

Forested land

Translocation

Dry and wet
deposition

Dry and wet
deposition

Inhalation

Translocation

Ingestion(drinking water)
Ingestion(forest products)

Translocation

Ingestion(agricultural
products)

FarmlandResidential areas

Sea

Ingestion(seafood)
The publicFig. 1 An interaction matrix which describes the migration of released substances in the general environment.
The diagonal elements are components of the system and the off-diagonal elements are the interactions between
them. To identify the transfer processes the matrix should be read clockwise from the upper left.

Analysis of environmental release and response in chemical accident“decontamination.” Regarding the responses to transfers
between media, examples of “Identification” responses
included “sensing odors (strange tastes)” and “personal
exposure measurement,” while examples of“Management” responses included “spraying water infirefighting,” “oil fence installation,” “mask wearing,”“indoor evacuation” and “limiting water supplies.”
In “Management” responses, an action may have a
new impact on substance migration between media. For
Table 3 P ossible responses for the components of the environmental
system in Fig.1.
Identification

Management

Accident site

On-site personnel interview
Use of notification information(e.g., PRTR)

Atmosphere

Visible plume,
Air monitoring,
Atmospheric dispersion modelRivers, Lakes

Death of fish,
Water quality monitoring

Diffusion prevention(e.g., oil fence)

Forested land

Damage to forest

Decontamination

FarmlandDamage to agricultural products Decontamination

Residential areas
Sea

Decontamination
Death of fish

Diffusion prevention(e.g., oil fence)

265

example, fire extinguishing activities may reduce theamount transferred to the atmosphere, but they may
increase the amount transferred to rivers or lakes or result
in releases of other substances. Therefore, it is also
important to sort out changes in the transfer process due
to passage of time or response actions.
It should also be noted that the process from release
to exposure varies depending on the accident type and thelocation of the release site. Emergency responses also
vary depending on the accident type, chemical propertiesof the substances involved, available capacity to deal
with accidents and so on. These classifications of media
and migration processes are tentative, and some
improvement may be needed. For example, scattering ofchemical substances by explosions to forested land fromindustrial sites is classified as migration via atmosphere,
but it may be more practical to classify such short-periodmigrations as direct migration. The blank cells in Figs. 1
and 2 do not necessarily indicate that a process does notexist or that a response is unnecessary, and it will benecessary to make corrections and additions in the future.
To lead to appropriate responses to future accidents ordisasters, it will be important to analyze release processes
after chemical accidents as comprehensively as possible
and examine responses that were (and were not) taken inpast cases and the reasons for that.

The public

Accident site

Constant
monitoring
Water spray

Atmospheremodel estimation?

model estimation?

model estimation?

model estimation?

model estimation?

Constant
monitoring
Interception(e.g., oil weir)Interception(e.g., oil weir)Odor, Personal
Deposition model Deposition model Deposition model Deposition model Deposition model
exposure
estimation
estimation
estimation
estimation
estimation
measurement
Evacuation/
Sheltering,
Mask wearing
Strange taste

Rivers, Lakes

Suspension ofwater supply
Strange taste

Forested land

Shipment
restriction
Strange taste

Farmland

Shipment
restriction
Residential areas

Sea

Strange taste
Shipment
restriction
The publicFig. 2 Possible responses to migration of chemicals. The top half of each square shows the identification responses
and the bottom half shows the management responses.

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Y. KOYAMA et al.

4. Conclusion
We conducted questionnaire and interview surveys
on chemical accidents and analyzed their characteristics.
From these surveys, it became clear that few
environmental surveys on the general environment havebeen conducted when accidents have occurred, and thatthe extent of information on released substances varies byindustry and type of accident. We have revealed that
information from existing notification systems such as
PRTR has been insufficient for identifying target
substances soon after accidents and it is important tocollect information on amounts of chemical substances
stored, including non-PRTR substances, for effective
responses to accidents. We have also systematicallyanalyzed release processes and the emergency responses
to them. Expansion of this information will enable rapid
and effective risk management of chemical substances
released into the general environment in emergencies.
Acknowledgements
This research was performed under the auspices of
the Environment Research and Technology Development
Fund (JPMEERF18S11701) of the Environmental
Restoration and Conservation Agency of Japan.

lg.jp/attach/4460/00157380/manual_saigai.pdf (Accessed 4
September 2020)
US Environmental Protection Agency, Acute Exposure Guideline
Levels for Airborne Chemicals. Retrieved from https://www.epa.
gov/aegl (Accessed 5 September, 2020)
World Health Organization (2009) Manual for the Public HealthManagement of Chemical Incidents. Retrieved from https://www.who.int/environmental_health_emergencies/publications/
Manual_Chemical_Incidents/en/ (Accessed 28 August 2020)

Yosuke KOYAMADr. Yosuke Koyama is a researcher at the Centerfor Health and Environmental Risk Research,
National Institute for Environmental Studies(NIES), Japan. He received his Ph.D. in
Environmental Engineering from Kyoto
University. He is interested in health andenvironmental risk management in emergencies
such as the aftermaths of chemical incidents. His research interests include
strategic approaches to comprehensive chemical risk management andcontrol, and indoor-scale chemical dynamics.

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Yoshitaka IMAIZUMIDr. Yoshitaka Imaizumi is a senior researcher at
the Center for Health and Environmental Risk
Research, National Institute for Environmental
Studies (NIES), Japan. He is interested inenvironmental risk assessment and management,
and relevant environmental fate models forchemical contaminants, including agricultural
pesticides, radioactive substances, and industrial chemicals. He has
investigated emission estimation methods and related fate models. He is
also contributing to the public disclosure of risk-related information about
regulations, amounts distributed, environmental monitoring results, andenvironmental measurement methods for chemicals, as part of his activitiesof the Risk Assessment Science Collaboration Office at NIES.

Noriyuki SUZUKI
Dr. Noriyuki Suzuki directs the Center for Healthand Environmental Risk Research at the National
Institute for Environmental Studies (NIES),
Japan. His research fields are chemical
contaminant risk assessment and relevant
environmental fate analysis based on both fatemodels and monitoring approaches. He chairs theWorking Group on PRTR at OECD and is also one of several working
members engaged in OECD and UNEP projects on chemical risk
management. He now is involved in a research project on integrating global
mercury emissions, fate/transport, material flows and impacts, in addition
to a project on chemical risk management in emergencies.

(Received 7 September 2020, Accepted 22 December 2020)