Microplastic opponents liken it to other substances that have become heavily regulated. “It took a long time with lead and tobacco,” said Sophie Constantinou, who serves on the San Francisco Park, Recreation, Open Space Advisory Committee. “We should at least say we have learned from these mistakes.”

Totaling about 40 acres, the Crocker Amazon park has been a site for team sports for nearly a century. On its southeastern corner are five existing artificial-turf soccer pitches. There’s also a skate park, tennis courts, playgrounds, and a clubhouse. In the early morning, joggers cut through the park, while Asian seniors exercise in groups.

For about five years, the Giants’ philanthropic arm has eyed the area as an opportunity to bring more baseball and softball to the neighborhood, according to team executive Jack Bair. He said inclement weather causes the grass fields to be unplayable for long stretches of time. That wouldn’t be a concern with turf, which has the additional benefit of not needing watering or mowing.