Spray used by British police forces to control aggressors more harmful than previously thought

A spray used by British police forces since 1995 to control or incapacitate an aggressor may be more harmful than previously thought.

The research is reported in the current issue of the Emergency Medicine Journal, a leading international journal of developments and advances in emergency medicine and critical care.

The "personal incapacitant" spray or PIS is used for self defence in situations where "lethal force is inappropriate." It combines the compounds CS (o-Chlorobenzylidene malononitrile) with MiBK (Methyl isobutyl keton).

o-Chlorobenzylidene malononitrile is a white crystalline solid with a pepper-like odor.

Methyl isobutyl ketone occurs as a colorless, flammable liquid that is moderately soluble in water.

The researchers collected information on 277 cases of PIS trauma submitted from healthcare professionals to the National Poisons Information Service in London for the first nine months of 1998.

The incidents were followed up with the attending medical professional by questionnaire, resulting in a total of 194 returned forms.

The circumstances of exposure to PIS were described in 152 cases. The average age of those on the receiving end was 26, and three quarters of them were men. Almost two thirds of these incidents (93 or 61%) were the result of an encounter with the police. The remainder had been sprayed by other people,

Of all the incidents, most spray was in the eyes or on the face, but in roughly a third of cases, the spray was breathed in. Streaming eyes, burning sensation, and blurred vision were most often reported.

But blistering, swelling, and skin inflammation also occurred; blistering and skin inflammation were significantly more common among people who had been sprayed by the police. And a higher proportion of patients who reported being sprayed by the police were referred for further specialist treatment.

More of those sprayed by the police sought treatment six or more hours after the incident, which suggests that either their symptoms were more severe, or that fear and/or arrests kept them from seeking help. PIS is designed to have effects that clear up quickly, say the authors.

"This study suggests that the CS preparation used by the UK police may cause more adverse effects than other PIS preparations," conclude the authors. Further research is warranted into the formulation, they say. And if confirmed, its use should be reviewed, they suggest.