Staff members of the Rachel Carson Homestead Association in Springdale showed up for a briefing at the Children's Museum of Pittsburgh on the North Side yesterday morning knowing only that there was going to an announcement that had something to do with the environment.

But they came away ecstatic: Not only was Ms. Carson's legacy invoked several times but they learned that Pittsburgh next year will be the North American host city for the United Nations Environment Programme's World Environment Day 2010.

"It's very exciting to have the opportunity to showcase Pittsburgh as an environmental center; we are really a leader and on the cutting edge," said Patricia DeMarco, executive director of the association that preserves the noted environmentalist and author's birthplace and offers environmental education and programming.

Civic and corporate officials who announced Pittsburgh's selection for the U.N. event touted it as an opportunity fresh on the heels of the G-20 summit for the city to share its story of transformation from gritty industrial town to a center for high-tech and green industries.

"Like during G-20, our region will once again be in the national and international spotlight," said Greg Babe, president and chief executive of Bayer Corp., which spearheaded efforts to attract the event.

World Environment Day, launched by the U.N. General Assembly in 1972, is held annually on June 5 to bring attention to environmental issues and how communities can work to promote sustainable development.

It is more than a one-day event, however, said Elisabeth Guilbaud-Cox, deputy director of UNEP. Activities surrounding World Environment Day begin with Earth Day on April 22 and continue for six weeks until June 5, she said.

Organizers already are promoting next year's event as "bridging the gap" between Earth Day and World Environment Day. "You could hold an activity every day," said Ms. Guilbaud-Cox.

Past events have included rallies, educational and scientific forums, school competitions, and arts performances and festivals pegged to an environmental theme.

Pittsburgh will host the event for North America; there will be six regional sites worldwide next year. It will be the fourth time the event was held in North America; previous host sites on the continent were Omaha, Neb.; Barrow, Alaska; and Chicago.

Several factors, including the recent G-20 summit held here and the region's significance as Rachel Carson's birthplace contributed to Pittsburgh's selection, said Ms. Guilbaud-Cox. The city has exhibited "leadership and commitment to sustainability issues" and its "transformation from old industry to a green economy sealed the deal."

Bayer's efforts in recent years to attract World Environment Day "played a pivotal role in choosing Pittsburgh," she said. "And having the G-20 recently didn't hurt either." Bayer, a German-based chemicals company, has its U.S. headquarters in Robinson.

The company began lobbying last year to hold World Environment Day here, said Rebecca Lucore, executive director of the Bayer USA Foundation who has worked with the UNEP for several years on youth programs.

She attended the last three events held in North America and began aggressively pitching Pittsburgh as a site "because I saw how much Omaha embraced it."

She expects collaboration between local government, businesses, foundations and non-profits to plan, sponsor and fund the events.

Officials said it was too early to estimate the cost of the event, how many individuals it could attract to the city or total economic benefit to the region.

"We learned a lot from G-20 about public and private collaboration," said Bryan Iams, Bayer spokesman. "There are a lot of similarities here about how do we make Pittsburgh known."

Allegheny County Executive Dan Onorato, who attended the announcement along with Mayor Luke Ravenstahl, said while World Environment Day is a chance for outsiders to recognize the region much as G-20 was, there will be one significant difference from the September summit that involved world leaders convening Downtown and at several other sites around town: "We'll need less security."

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