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US adopts science-based guidance for chemical-attack response

Comprehensive guidelines recommend wiping down with dry, absorbent materials.

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ASPR teams with local responders in Kingston, R.I. for Operation Downpour

US authorities tested emergency-response procedures for chemical attacks in a large drill in Rhode Island.Credit: ASPR

The US government has introduced science-based guidelines for how to swiftly decontaminate large numbers of people after a chemical-weapons attack or an industrial chemical accident.

The guidelines, published on 21 February, are the first in the United States to be based on extensive on research and testing. They recommend that emergency responders instruct people to quickly undress to their underwear and wipe themselves dry with absorbent materials, such as paper towels and bandages supplied on the scene. Tests showed that this ‘dry decontamination’ method removed 99% of chemicals from a person’s skin, when carried out properly.

The guidance also highlights that it’s crucial to give individual assistance to people who need it, for example those who have disabilities that restrict their movement, or who have difficulties understanding instructions.

Terrorist threats and the use of chemical weapons in Syria have heightened awareness of the need for improved preparedness against chemical attacks, says Gary Disbrow, deputy director of the US Biomedical Advanced Research and Development Authority (BARDA), which prepared the guidelines. “First responders are supportive of the fact that it is evidence-based guidance, and not just, ‘We used this last time and it seemed to work’,” he says.

US authorities and BARDA, part of the US government’s health department, are now encouraging regional US emergency services, which individually decide on response procedures to chemical incidents, to adopt the guidelines. There are hundreds of chemical incidents in the United States every year but most are small; the guidelines are geared towards helping emergency services prepare to respond to mass-casualty events such as a chemical-weapons attack in a densely populated area.

Since 2012, BARDA has worked with one of the world’s leading toxicology research labs — at the University of Hertfordshire in Hatfield, UK, led by Robert Chilcott — to develop the guidance.

The guidelines mark a shift away from the US mainstay of decontamination preparedness, the ‘ladder pipe’ system. In this method, two fire engines parked in parallel create a decontamination ‘corridor’ through which people walk while the trucks spray water sideways and from overhead. Victims may later receive more specialized cleaning involving scrubbing. But the ladder-pipe takes about 20 minutes to set up and many chemicals can cause harm more quickly. The cold water is also unpleasant and distressing, says Chilcott. “The problem with wet decontamination is hypothermia, even on warm days, as well as peoples’ reluctance to strip off and walk through a cold water shower,” he says.

ASPR teams with local responders in Kingston, R.I. for Operation Downpour

The ‘ladder pipe’ method of decontamination has been the default for US emergency services.Credit: ASPR

Chilcott and BARDA’s research on decontamination methods culminated in a large-scale exercise in August 2017 called ‘Operation Downpour’ at the University of Rhode Island involving dozens of volunteers. People were sprayed with a harmless solution — a mixture of curcumin (which gives turmeric its yellow colour), solvents and baby oil, which mimicked the properties of chemical weapons such as sarin and mustard gas.

The exercise tested combinations of methods: dry decontamination using absorbent bandages, the ladder-pipe system, and ‘technical decontamination’, in which specialized teams scrubbed volunteers with water and detergents. Researchers then used fluorescent, whole-body imaging and tested skin swabs to reveal the procedures’ efficacy.

Used together, the three measures removed 100% of chemicals from people’s skin. Dry decontamination used with either of the other two measures achieved 96% skin decontamination, on average. But people who followed dry-decontamination instructions to the letter achieved up to 99% using that method alone. People who didn’t comply fully with the guidelines, through misunderstanding or because of disabilities that restricted their movement, decontaminated only around 70% of their skin.

The researchers were also surprised to find that hair is nearly impossible to decontaminate properly, meaning shaving it off is likely to be the safest option, says Judy Laney, chief of BARDA's Chemical Medical Countermeasures programmes. “No one had really looked at this aspect before,” she says. People may be averse to having their heads shaved — but it is crucial to remove any contaminated hair, and to protect first responders, hospitals and doctors, she says. “I think people told that they have, say, mustard gas in their hair are going to be willing to have it cut,” says Laney.

Disbrow hopes that a smartphone application the team has developed in conjunction with the guidance will increase take up of the guidelines by emergency services, which are used to the default ladder-pipe system. The agency is trying to promote adoption of the guidelines through field exercises and presentations, says Laney, but it won’t happen overnight.

The app, called ASPIRE (Algorithm Suggesting Proportionate Incident Response Engagement), helps responders to determine the best decontamination approach for the chemical involved. It also features a tool based on a mathematical model to predict the amount of skin contamination in an incident any time after exposure, based on how quickly a given chemical evaporates.

The app is based on research by Chilcott’s team, which measured how quickly various doses of different chemicals evaporated from an artificial skin. ASPIRE may, for example, predict that all of a contaminant has already long evaporated and that decontamination isn’t needed — or suggest which cleaning methods are most appropriate. That could help to prevent unnecessary use of the ladder-pipe, says Chilcott.

Disbrow says that he hopes that governments and first responders elsewhere — especially in the Middle East — will use the guidelines. Videos of chemical weapons attacks in Syria, the latest of which was suspected to have occurred last year, suggested that people lacked the basic information needed to try to quickly decontaminate themselves, he says.

Susannah Sirkin, director of policy at New York-based Physicians for Human Rights, which has advised frontline health workers in the Middle East on chemical attacks, agrees that the guidance will be helpful for responders in war zones. “In the midst of armed conflicts, simple information and training for dry decontamination and self-protection, clearly communicated in local languages, are vital,” she says.

doi: 10.1038/d41586-019-00646-4
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