Sometimes to get people to listen, some would say, you need a mother's touch. And a child's smile doesn't hurt, either.

Trisha Sheehan knows this. On a sunny day last month, Sheehan arrived at a Paulsboro park by the Delaware River with her 5-year-old son, Liam, as environmentalists gathered to lambaste the state's proposed contamination settlement with ExxonMobil Corp. The boy offered a quiet hello from his mother's arms before she spoke against the deal.

"It's their future planet that we need to be protecting," Sheehan, 35, said recently at her Wenonah home, where Liam ran about in a red shirt bearing the name of Moms Clean Air Force.

Before Sheehan joined the national group, which fights air pollution and boasts about 500,000 members, she had no experience in such advocacy. She had not dabbled in press conferences, federal legislation, or what the group calls "naptime activism."

She started to educate herself on healthy, eco-friendly household and personal care products after she and her husband, Mike, a carpenter, had Logan, now 9, and Liam. But a 2012 train derailment shifted her life's trajectory.

When the 82-car freight train derailed over the Mantua Creek in Paulsboro on Nov. 30 that year, Sheehan's former neighborhood in Woodbury was instructed to shelter in place. Four rail cars fell into the creek, causing one to rupture and leak 20,000 gallons of toxic vinyl chloride, a carcinogen, into the air. Sheehan remembers the odorless chemical's sweet, burning taste on her tongue.

"I thought I did everything I could to protect my kids," she said, recalling using towels to block the cracks of windows and doors, and turning on an air purifier.

Still, Sheehan became nauseous, had a migraine, and vomited. Logan also got sick. Liam, who appeared unaffected at the time, now bleeds upon even the slightest of impacts to his nose - which Sheehan believes is a lingering effect from the chemical infiltrating his nostrils.

"This is why I do the work that I do," said Sheehan, now the Northeast regional field manager for Moms Clean Air Force. "To protect other families and communities from the impacts of chemical exposure, and the fossil fuel industry, and air quality issues."

It wasn't necessarily the future Sheehan had imagined.

A Mickleton native, Sheehan grew up on a large farm where her parents grew peppers, asparagus, tomatoes, and other produce. She loved the outdoors and "would run across rocks barefoot," as she put it.

The Kingsway Regional High School graduate went on to study marketing, earning a master's degree from Goldey-Beacom College in Wilmington. She had plans to one day find work doing branding for a major firm.

"That's really what I thought I would do, until I had children," she said. She came to a realization: "I can't sell something I don't believe in."

Taking care of her kids, Sheehan became conscious of how certain household and personal products could affect the boys, especially when Logan was a baby and experienced breathing issues after playing on a newly laid carpet at her sister's home - a problem a doctor attributed to chemicals used for the floor. The family also learned to be cognizant of the ingredients in its food.

Those environmental baby steps turned into a sprint after the train wreck. After the accident, Sheehan contacted Moms Clean Air Force, an extension of the nonprofit Environmental Defense Fund, and began volunteering. In early 2014, she started a New Jersey chapter, and by November was hired to her current full-time job.

"The derailment in Paulsboro was a public-health catastrophe that did open the eyes of a lot of people living around there . . . about what's carried on the trains," said Tracy Carluccio, deputy director of the Delaware Riverkeeper Network, who has done some work with Sheehan. "Some people would feel victimized by that, but what Trisha did was stand up and say, 'I'm not going to be a victim.' "

Sheehan can now be found wielding signs and passing out stickers ("I Listened to a Mom," one reads) to lawmakers in Trenton and elsewhere. By her side often are at least one of her sons. Early on, she took part in a mom-friendly march referred to as a "stroller brigade."

Moms Clean Air Force is urging Congress to limit carbon pollution from power plants. To that end, the group will hold a "play-in" July 7 in Washington with children's activities. The group will deliver large cards with signatures to senators for each state, asking them to combat climate change.

Sheehan has traveled to Missouri and Texas, and was recently named to an advisory board for the Columbia (University) Center for Children's Environmental Health, which researches the health effects of children's exposure to certain pollutants.

"Organizing is a hard thing to do, but [Sheehan] can . . . really galvanize" support, said Gretchen Dahlkemper, national field manager for Moms Clean Air Force. A mother of three who lives in the Point Breeze section of Philadelphia, Dahlkemper has a 4-year-old, Fiona, who suffers from asthma.

"Air pollution in and of itself is a big issue, and it's oftentimes invisible," Dahlkemper said. "The solutions for taking care of air pollution are so big and so scary," people don't think about it until it personally affects them.

Despite the organization's name, the group boasts women and men (its social media director, for instance, is a dad). And then there are the kids.

Liam once helped deliver comments regarding ozone regulations to a U.S. Environmental Protection Agency official. Logan, Sheehan recalled, helped lead a rally at a hearing regarding the EPA's proposed Clean Power Plan last year - "What do we want?" the boy cried out to a crowd, which responded: "Clean air!"

"He's definitely following in my footsteps," Sheehan said.

856-779-3917 @AJFichera