WHAT CAN THEY be thinking of in the Prince George's County prosecutor's office? The police have been engaged in a drive to stamp out traffic in PCP, perhaps the most damaging illegal substance being sold on the streets today. Since the middle of the summer, undercover men and informers -- at no little personal risk -- have been working to make arrests, and their very success has, it seemed, backfired. Prosecutor Arthur Marshall's office claims that it cannot handle all these felony prosecutions and has been reducing many of the charges to simple misdemeanors.

Surely, these prosecutors know about PCP. They must know that this drug often causes users to act violently, that police in many jurisdictions can spot them right away because they are the ones who behave in a manner that is not only dangerous and out of control but often unrelated to reality. Heroin addicts often commit crimes of violence to get the money to buy nacotics, but PCP users act violently simply because this is the effect the drug has on them. It can also cause severe and irreparable brain damage, as physicians in every emergency room and mental health facility in the area will tell you.

Selling this poison is effectively an act of violence that results, in many cases, in terrible permanent injury. Prosecutors in the District think so, and have brought a record number of PCP cases and lobbied for more treatment and incarceration facilities. Of course, it puts a burden on the prosecutors and the courts. But Circuit Court Judge Howard Chasanow put their obligation in context when he asked whether an outbreak of armed robberies should result in more lenient treatment of those arrested simply so that their cases could be processed more efficiently.

If Prince George's residents don't want their county to be known as an easy market for these despicable PCP pushers they should insist on a tougher policy and be willing to provide the resources to carry it out. Those who deal in this extremely destructive trade should be prosecuted as the dangerous felons they are.