Massive population increases are overwhelming many of the world's largest cities, threatening the quality of life for current residents and newcomers, a population-control group warns.

A two-year study of the quality of urban life concluded that fast-growing cities such as Lagos, Nigeria; Kinshasa, Zaire; and Dhaka, Bangladesh, have the worst living conditions.The best places to live, according to the analysis of the 100 largest metropolitan areas in the world, are Melbourne, Australia; Montreal, Canada; and Seattle-Tacoma, Wash.

The study was conducted by the private Population Crisis Committee, which analyzed the communities, awarding up to 10 points in each of 10 categories.

Melbourne, Montreal, and Seattle-Tacoma each accumulated 86 of the possible 100 points. Lagos scored only 19 points."More than half of these cities are sinking from the weight of too many people," said Sharon L. Camp, senior vice president of the population group. "More than anything else, the numbers developed in (the study) add up to human population overload."

Water, roads, sewers, electricity and other basic services cannot keep up in rapidly growing areas and will never do so if such growth continues, she warned.

Camp stressed that the study is not a guidebook for retirement or business or vacations but rather a warning about the dangers of rapid population growth.

Lagos, for example, averages 5.8 people per room in living space, only half of the houses have water and electricity, and there is only one telephone per 100 people in the city.

By comparison, Melbourne and Montreal average 0.5 people per room in housing and Seattle-Tacoma has 0.4. All residences in those cities have water or electricity or both. Seattle-Tacoma has 106 telephones per 100 people, while there are 69 in Montreal and 45 in Melbourne.

Residents of the top-rated communities welcomed the findings.

"Montreal, like all other major economic and cultural centers in the world, has to deal with major social and environmental issues. But our city has an important advantage over other big cities - Montreal wants to preserve its heritage," said Mayor Jean Dore.