Demonstrators in Louisiana stepped off on a five-day march on Thursday, demanding environmental justice for a region besieged by toxic pollution from chemical plants.

The protest began just a few hundred feet from a factory in Reserve, Louisiana, that presents the greatest risk of cancer to the surrounding community of any in the nation, according to government data.

Standing outside an elementary school barely beyond the facility’s fence line, activist and resident Robert Taylor demanded the plant be shut down.

“We are demanding not only the saving of our children at this school, we are demanding the salvation of this entire area,” said Taylor, director of a local citizens group, which has been organizing around lowering the plant’s emissions since 2016.

He continued: “Up and down this river they are poisoning our communities with impunity. We have implored [the factory] to get down to at least what the EPA says is a safe level. They have refused to do that and based on that, they need to shut down.”

Taylor was joined by dozens who assembled on a sweltering May day in southern Louisiana calling themselves the “coalition against death alley”. The groups also included protesters from environmental groups in New Orleans and St James parish, where activists are fighting attempts from the Taiwanese plastics giant Formosa to site a new facility that would potentially be the world’s largest. “St James is full,” one protester’s sign read.

The group’s demands include that all healthcare costs incurred by local residents related to toxic pollution be covered, banning industrial emissions within five miles of public areas, and the end to favorable tax exemptions for industry in the state. The march is scheduled to go from Reserve to the state capitol in Baton Rouge over a five-day span.

Play Video 7:57 'People are dying horrible deaths': the Louisiana town where cancer haunts the streets – video

The demonstration comes in the same month the Guardian launched a year-long reporting project, Cancer Town, from Reserve, which will follow the stories of residents here and in other communities in the area between New Orleans and Baton Rouge, known colloquially as Cancer Alley.

Reserve is home to the census tract in America with the highest risk of cancer due to airborne toxicity, according to government science. That risk, 50 times the national average, is almost entirely due to a plant, the Ponchartrain Works facility, operated by the Japanese manufacturer Denka. The plant is also the only place in America to manufacture the synthetic rubber neoprene, which is composed of the polymer chloroprene listed by the federal Environmental Protection Agency (EPA), as a “likely carcinogen”.

Campaigners have called on Denka to drastically lower emissions from the plant to 0.2 micrograms per cubic meter – the recommended safe level. Government-installed air readers close to the plant routinely detect chloroprene dozens of times above this level. On Thursday most of the marchers wore red T-shirts with the words “only 0.2 will do” on the front.

In 2017 Denka entered into a voluntary agreement with Louisiana’s state environment agency LDEQ, to reduce emissions by 85%. But earlier this month, the state agency warned the company that readings in early 2018 indicated the company had not yet reduced its emissions to this level.

In a letter dated 16 May 2019, seen by the Guardian, the LDEQ assistant secretary Lourdes Iturralde instructed Denka to supply within 30 days data showing the plant had reduced emissions.

“If chloroprene emissions have not been reduced by at least 85%, the Department requests DPE [Denka] to submit a schedule of further measures to be undertaken by DPE to further reduce chloroprene emissions,” the letter states.

A spokesman for Denka said the company was currently “developing a snapshot of emissions” to respond to LDEQ’s inquiry. The response would include emissions data from after the full construction of offset technology. Denka did not respond to a request for comment on the protest march.

Meanwhile, at the protest, 58-year-old Wayne James bicycled along the march with his protest sign tucked into a rear basket. Having recently had cancer-related surgery he could not walk far, but didn’t want to miss the opportunity to make his voice heard. “They’ve been killing us for too long,” he said, shaking his head.

The lifelong Reserve resident added that in recent weeks he discovered that one of his best friends, another local, had been diagnosed with kidney cancer.

“When I was in the hospital for three months he came and visited me. Now I’m out here visiting him, it’s crazy,” James said. “So I’m marching for him.”