Its creator, Jackie Brookner, an artist from Manhattan, said the piece, which was designed with the help of biologists, acts as a natural pollution filter.

Just as clean natural waters can be a rare treasure of a country, natural pollution is also a characteristic that we must accept, especially when there is nothing we can do about it.

This may be very concentrated and create many problems, but it is industry which is responsible for 60% of pollution. And, by way of an indication, 10% is caused by natural pollution.

But the study said that the rockets' contribution to these problems was so small relative to other industrial, consumer and natural pollution sources that there was no need for urgent action, like curtailing flights or rushing alternative fuels into use.

Any development of land near the Marshlands Conservancy, the only viable marshland on Long Island Sound between New York City and Westport, Conn., would be detrimental to the natural habitat and would rob the Sound of a natural pollution filter.