Incident Investigations

What is ACE?

When toxic substance spills or chemical emergencies happen, ATSDR helps state and local health departments by providing ACE resources to perform a rapid epidemiologic assessment.

Webinar on ATSDR Assessment of Chemical Exposures (ACE) Program

What happens during an ACE investigation?

ACE talks with incident responders and hospital staff that treated patients to understand

• what happened,
• who was exposed,
• steps taken to protect public health, such as an evacuation or shelter-in-place order,
• communication during the response, and
• lessons learned during the response.

ACE also interviews people who may have been exposed to collect detailed information on

• exposure history,
• symptoms experienced,
• who was exposed,
• health services used,
• needs resulting from the exposure,
• medical history,
• how people received information about the release, and
• health impacts on pets.

ACE typically reviews hospital medical charts and veterinary chart abstractions to learn more details about health effects experienced as a result of the release. ACE may also assist in collecting and analyzing clinical samples if a laboratory test is available to determine exposure to the substance. If testing is done, results are sent to participants to share with their physicians.

Why perform an ACE investigation?

State and local health departments can use information obtained from rapid assessments to

• assess impact of the release on individuals as well as the community,
• direct the public health response,
• target outreach to prevent similar incidents,
• assess the need to modify emergency response procedures, and
• identify a group of exposed people that may need to be followed-for long-term effects.

A body of data from multiple incidents can be used for education and training to prepare for future incidents.

What are some examples of ACE investigations?

The ACE team worked with the state or local health agency on the investigations and public health actions described below. Additionally, ATSDR has partnered with other public health and safety agencies, like the National Institute for Occupational Safety and Health (NIOSH) to work on chemical releases. The goals of each investigation were determined by the inviting agency. Each investigation involved multiple components, including interviewing responders and owners/managers of facilities, surveying exposed persons and staff at hospitals where patients were treated, and reviewing hospital charts for patients treated for chemical exposure.

Chlorine release at a metal recycling facility
Chlorine gas was released when a 1-ton, low-pressure tank was cut at metal recycling facility. Most workers and customers followed the planned evacuation route, exiting the facility through the main gate and meeting in an open field that was downwind from the tank. The ACE team, working with the state and local health department:

• Interviewed responders and facility owners, surveyed exposed persons, and the state partners abstracted hospital charts. A report of the investigation has been published.
• Prepared a chemical release alert [PDF – 618 KB] to send to metal recycling facilities throughout the state. The alert was also made available in Spanish [PDF – 426 KB]. Key messages included:
  • Only accept containers that are cut open, dry, and without a valve or plug.
  • Treat closed containers as potential hazardous waste.
  • Develop and practice an evacuation plan. Train workers to stay upwind when evacuating for a chemical release.
• The state health department conducted follow-up interviews and medical record review of the affected workers 6 months after the incident, determining that some workers had ongoing respiratory and psychological symptoms. As a result of their findings, they provided technical assistance to the treating providers.

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Ammonia release at a refrigeration facility
A pipe ruptured on the roof of a refrigeration facility, releasing anhydrous ammonia. A cloud of ammonia drifted over a canal behind the facility, exposing personnel on ships docked at the refrigeration facility and at a large facility across the canal where work was taking place outdoors. The ACE team, in conjunction with the local health department and the state’s CDC Career Epidemiology Field Officer:

• Interviewed personnel at the refrigeration facility, responders, and employees of a large facility that was downwind; surveyed exposed persons at the downwind facility; and reviewed hospital charts. County partners surveyed hospitals where patients were treated.
• Participated in a Hotwash (after action review) of the response to the incident and reported that there was a lack of notification of the people in the area of the release. The county later obtained a reverse 9-1-1 system to be able to call telephones belonging to residents and businesses in a defined geographic area and deliver recorded emergency notifications.

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Chlorine release at a poultry processing facility
A worker accidently mixed sodium hypochlorite with an acid-containing disinfectant, releasing approximately 40 lbs of chlorine gas within the facility. Due to the air flow within the building, workers were exposed both at their work stations and in a major hallway used as an evacuation route. The ACE team, assisting the state and local health department:

• Partnered with NIOSH on the investigation. The NIOSH team performed a Health Hazard Evaluation at the facility and surveyed workers to learn their health effects.
• Interviewed responders, surveyed staff at hospitals where patients were treated, and reviewed hospital charts of patients treated for chlorine exposure.
• Determined that the existing emergency response protocols had an excessively high threshold for notification of the health department about chemical incidents. After the ACE investigation identified the issue, the notification protocol was modified to include health department notification of any incident involving a biological, chemical, radiological, or nuclear substance.

Published results of the investigation Challenges During a Chlorine Gas Emergency Response

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Vinyl chloride release from a train derailment
A tanker car punctured during a train derailment released approximately 24, 000 gallons of vinyl chloride on the edge of a small town. A shelter-in-place order was established for surrounding areas, then was lifted and reestablished repeatedly over four days, as vinyl chloride levels in the air fluctuated due to weather conditions. The ACE team, in partnership with the state and local health department:

• Surveyed community members who were potentially exposed, surveyed staff from hospitals where patients were treated for vinyl chloride exposure, surveyed staff from a facility whose only access road was blocked by the derailed train, and performed hospital chart abstractions. State partners mailed a survey to all households in the community.
• Partnered with a NIOSH team which interviewed representatives from responder groups and created a written survey for responders. A report of the NOISH investigation has been published.
• Answered responders’ questions during their meetings and collected information needed to address community concerns.
• Reports from investigations of the incident are available at:

Paulsboro Fact Sheet on Health Survey Findings/Air Quality Impacts Following Vinyl Chloride Gas Release: September 2014 [PDF – 33 KB]

Paulsboro Health Consultation Survey of Residents Following Vinyl Chloride Gas Release: September 2014 [PDF – 2 MB]

Paulsboro Air Quality Health Consultation Following Vinyl Chloride Gas Release: September 2014 [PDF – 2 MB]

Q & A on Health Effects of Vinyl Chloride: December 2012 [PDF – 307 KB]

Q & A on Community and First Responder Health Surveys: December 2012 [PDF – 304 KB]

Published results of the investigation:  Assessment of emergency responders after a vinyl chloride release from a train derailment New Jersey 2012

Exposures and symptoms among workers after an offsite train derailment and vinyl chloride release

Medical Response to a Vinyl Chloride Release From a Train Derailment New Jersey 2012

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4-Methylcyclohexanemethanol and propylene glycol phenyl ether contamination of a public water supply
A tank containing chemicals used in coal processing leaked into a river just upstream from the intake of the municipal water supply for approximately 300,000 people. A “Do not use” water order was issued for a nine-county area. The ACE team, working with the state health department:

• Performed hospital chart abstractions for patients treated for exposure to the contaminated water. Surveyed area hospitals to learn of their experiences with the “Do Not Use” water order. A review of disaster epidemiology capacity within the inviting agency was also performed.
• Used results from the hospital chart reviews for local outreach and education efforts in an effort to alleviate the public’s concerns about spill-related health effects. Findings of the hospital survey were used to provide information to hospitals planning for emergencies where their water supply is compromised. The disaster epidemiology capacity report was used to aid in planning for health department responses to future disasters.

Published results of the investigation : Hospital Impact After a Chemical Spill That Compromised the Potable Water Supply: West Virginia, January 2014.

Acute Health Effects After the Elk River Chemical Spill, West Virginia, January 2014

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Methyl bromide exposure at a condominium resort

Methyl bromide, an outdoor pesticide, was inappropriately used as a fumigant at a condominium resort in the U.S. Virgin Islands. A family of four were exposed and developed life threatening illness. Thirty seven others were potentially exposed. The ACE team, in partnership with the local health department:

• Worked with the EPA and condominium management to identify additional persons who were potentially exposed to methyl bromide;
• Interviewed exposed persons using a standardized questionnaire about possible exposure related health effects;
• Published results of the investigation: Severe Illness from Methyl Bromide Exposure at a Condominium Resort — U.S. Virgin Islands, March 2015.

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Flint rash investigation
On April 25, 2014, the City of Flint, Michigan switched its drinking water source from Lake Huron to the Flint River and on October 16, 2015 they switched it back to Lake Huron. During this time, people were presenting to their health care providers with rashes or worsening rashes. The ACE team assisted the local health department to

• Design a survey specifically for this study which was administered to Flint residents who reported rashes between late January and March 2016. Investigators were able to interview 390 people.
• Refer people to four dermatologists from the Flint area who volunteered to give investigation participants free dermatology evaluations. They examined 122 people.
• Partner with the Environmental Protection Agency (EPA) between January and May 2016 to conduct water-quality tests. Water samples were taken from 170 homes in Flint where rashes were reported.
• Review historic water-quality data that the Flint water treatment plant produced when the Flint River was the city’s source for municipal water.

A report from the investigation and fact sheet are available at
https://www.phe.gov/emergency/events/Flint/Documents/rash-report.pdf

https://www.phe.gov/emergency/events/Flint/Documents/rash-study-factsheet.pdf