The film "A Chemical Reaction" will be shown at First Parish in Needham, 23 Dedham Ave., on Tuesday, April 24 at 7:15 p.m.

The film tells the uplifting story of a Canadian town that started a widespread movement in Canada to ban toxic lawn pesticides. After the 55-minute film, a panel of experts will answer questions and discuss health concerns associated with pesticides and how to reduce use and exposure.

Panelists will be Chip Osborne, who has been managing Marblehead's town fields organically for 10 years; Sara Wylie, who will speak on the health implications of endocrine disruption; and Needham resident Ellen Fine, who directs the LEAH Collective, a group promoting organic alternatives to toxic pesticides.

The event is free. Doors will open at 7 p.m. Seating is limited; advanced registration is encouraged. Please register at april24achemicalreaction.eventbrite.com.