Earlier this month, the Independent on Sunday revealed how police were using the spray to restrain mentally ill people in hospitals, police stations, and even their own homes.
Now, an editorial in The Lancet, one of the profession's most influential journals, calls for the "chemical baton" to be withdrawn from officers on the beat until more research is conducted into its health implications.
The Lancet's position represents a serious challenge to the claims of police chiefs and the Home Office that CS is not dangerous for the user and bystander, and is a relatively innocuous incapacitant. It also adds weight to the deep concerns voiced by mental-health experts and civil liberties campaigners in recent weeks about the misuse of CS spray.
The Lancet claims CS spray has been "under-investigated", saying: "There are concerns that the effects on the victims are not as benign as was thought." It concludes: "It is right to question policy when safety remains in doubt. Until police authorities can publish or cite adequate safety studies, there should be a moratorium on the use of CS spray."
The Lancet also argues that because CS lingers, it is an occupational health issue, too, for police officers, police doctors and accident and emergency personnel. Police doctors in Bedfordshire, fearing the effects of secondary exposure, are refusing to attend to prisoners in custody who have been sprayed, it says. But a spokesman for Bedfordshire Police said there was no record of this happening.
CS spray is designed to have an instant effect and is supposed to be used only on violent or armed suspects. It blinds the target, causes breathlessness and burns and blisters the skin. But the effects are meant to be only temporary and to cause no lasting harm. It is this last point that is being questioned by doctors.
One survey showed that of 34 people sprayed, only two recovered in the prescribed period of 15 minutes and more than half were still suffering symptoms such as blistering, watery eyes and breathing difficulties more than a week later.
The long-term damage to the eyes is of utmost concern to doctors. Peter Gray, a consultant ophthalmologist, explained: "CS causes the protective layer across the eye to become denuded, which will allow infective organisms to enter the eye, and this infection, once it sets hold, can lead to blindness."
Police chiefs defend CS spray as the key to reducing injuries to officers. Avon and Somerset Constabulary, for example, has seen a 20 per cent drop in injuries since CS spray was issued to its 2,500 front-line officers.
A spokesman for the Association of Chief Police Officers (Acpo) said the CS spray safety concerns were being, "grossly exaggerated". He added that "the next generation of [safer] CS spray" was being studied by Home Office scientists.
Concern about the use of CS spray by police is not limited to those on the receiving end. Even in the force, serious reservations about its safety exist among a minority of officers. The first victims of long-term health problems caused by CS spray were, in fact, police officers.
Internal police testing of the new CS sprays began in 1995 but was aborted after several serious injuries. A Metropolitan police inspector was reported to have suffered 50 per cent burns to the cornea of one eye and 40 per cent to the other.
Dr Jill Tan, the Home Office scientist responsible for approving CS spray, was injured in one of the early tests. Only water-filled canisters are now used in training exercises.
All but three police forces have now implemented CS spray, but Nottinghamshire, Northamptonshire and Sussex have refused because of doubts over its safety. In Northamptonshire, 70 per cent of police voted against CS spray being issued.