Visiting the Pope may be hazardous to your health.

At least, medical personnel around Boston seem to think so. They are putting together an elaborate network of medical facilities to serve the unprecedented crowds expected October 1 on Boston Common to celebrate Mass with Pope John Paul II.

Boston hospitals and the American Red Cross will set up nine first-aid stations in the common, and more than 30 special ambulances--both public and private--will be on duty during the Pope's visit, Lenworth Jacobs, director of emergency services for Boston City Hospital, said yesterday.

City health department officials expect 500,000 people on the Common, many of whom will be elderly, Jacobs said.

President Bok recently announced Harvard employees may take the afternoon of October 1 off to go to the Mass if they are not involved in crucial University activities.

Some courses, such as Government 30, "Introduction to American Government," will reschedule classes because of the Pope's visit and Yom Kippur, which fall on the same day.

Medical care for the Pope will begin as soon as he lands at Logan Airport, when paramedics and a doctor will join his motorcade. Until his entourage leaves the South End, Boston City Hospital will be responsible for his care. When he gives the Mass on the common, Harvard-affiliated Massachusetts General Hospital (MGH) will take responsibility for him and for any crowd emergencies. St. Elizabeth's Hospital will take care of medical problems of the papal motorcade en route to the home of Humberto Cardinal Medeiros, Jacobs said.

Jacobs added he expects a lot of people to come down with colds, especially if the weather is bad. "And any big crowd--no matter how peaceful--has its share of cuts, bruises and sprains," he said.

Jacobs said he cannot estimate the cost of the increased health care, because all of the Boston area teaching hospitals with emergency rooms will be gearing up their staffs for the crowd.

At MGH, an extra volunteer force will start working Saturday, September 29 and continue through Tuesday, October 2 in the emergency room. MGH normally handles about 1000 out-patients a day, Martin Bander, deputy to the general director of MGH, said yesterday. He added emergency problems normally tend to be most severe on Mondays.