Mitchell Montgomery said he knew there was something curious about his new home when he moved in last year, surrounded as it was by empty streets and overgrown lots — and priced below the going rate for many rental houses in Niagara Falls.

When he brushed his teeth, for instance, he sometimes noticed a peculiar smell coming through the drain. It seemed like his 8-year-old son’s asthma was getting worse, and his pregnant girlfriend was having occasional nosebleeds and headaches.

And a couple of months ago, when he replaced a sump pump in the basement, it was covered in a thick tar-like substance.

“It was just black,” he recalled.

But none of these things struck him as too suspicious until he realized what was underneath the large, empty swath of grass, sealed off by a tall chain-link fence, just two blocks from his front door.

The Niagara Falls mayor, Robert Restaino, said in late May that he had been unaware of the new arrivals in that part of Love Canal and had asked his planning department for a report.

Informed of the sales, state officials said they, too, would continue “oversight of the area.” They also said they would work to determine if the state needed to make any updates to requirements for such property transfers, while saying that the sale of Mr. Montgomery’s home was allowed, as were several others of properties and parcels in the eastern area.

Still, Mr. Montgomery said he had no idea of the neighborhood’s history until a recent conversation with a New York Times photographer. “I just really want to know, because if it’s hazardous, then they’re putting my family in danger,” he said.

Mr. Mitchell’s landlord, Heather Moudy, said she bought the property last year from a woman that had been living there and may have been “a Love Canal baby.” And while Ms. Moudy said she had known about the history of Love Canal, having lived in Niagara Falls, she didn’t recall if the proximity to the site had been specifically noted at the time of the sale.

“I don’t know if anybody raised a red flag to me,” she said.

“They say everything has been remedied,” Ms. Moudy said, adding, “But right now, it’s a little bit of a worry in my head. At the same time, people have lived over there.”

State and federal officials insist Love Canal is safe: Since the site was identified as a public threat in 1978, prompting the creation of the Superfund law to clean up hazardous waste sites, a series of containment and monitoring measures have been implemented. A clay cap was placed over some 40 acres, which is dotted with testing wells. Contaminated soil was removed and local creeks and sewers have been cleaned, even as tons of toxic chemicals still sit buried beneath the fenced-off site.

All told, nearly 1,000 families were evacuated and hundreds of homes were demolished in the 10-block area adjacent the Love Canal landfill, according to the E.P.A. Some families, however, refused to move from the so-called Emergency Declaration Area.

Cleanup work was completed in the late 1990s, and the agency now says “the site no longer presents a threat to people’s health and the environment.” In 2004, it was removed from the Superfund list.

But the state’s rules for the neighborhood’s “habitability” are still governed by a 1988 decision by the New York Department of Health, which says the eastern portion of the neighborhood is “not now suitable for residential use.” Areas to the north and west of the site are deemed safe for residents, though streets to the immediate west are largely vacant.

But Niagara County property records show four sales of homes in the nonresidential area to the east of the canal from late 2020 through 2022, for between $45,000 and $65,000, significantly below the going rate for nearby neighborhoods.

The State Department of Environmental Conservation says that “there are no deed restrictions that would have precluded transfer or sale of the properties or triggered state review of the transactions.”

“DEC is working with our state and federal partners to ensure all appropriate notifications and institutional controls are up-to-date for area properties,” the department said in a statement.

Regardless of official assurances, the sales have alarmed some of the activists who helped bring the original crisis to light, including Luella Kenny, who lived near the canal at the time of the evacuations and whose child — wracked by seizures, hallucinations and other ailments — died in 1978.

In a recent letter to the mayor, Ms. Kenny expressed shock that “houses in the uninhabitable section of Love Canal are being resold and rented,” adding that “the trust we placed in Niagara Falls” is gone.

Walking around the areas that have been repopulated, Ms. Kenny, who is 86 and a former research scientist, seems astonished that some have forgotten the legacy of Love Canal.

“They’re trying to pretend it’s a normal place,” she said, standing next to a handsome playground, perhaps 100 yards from the site’s perimeter fence. “And it’s not a normal place. I’m sorry.”

The history of Love Canal dates to a smooth-talking developer, William T. Love, who had promised in the late 1800s to build an urban utopia called Model City near the banks of the Niagara River, just south of the world-famous falls. The key to the plan was hydroelectric power, which Mr. Love wanted to produce with a canal diverting the waters of the Niagara.

But Mr. Love’s promises proved empty and he fled town, leaving behind an unfinished and frequently waterlogged ditch, often co-opted by local children looking for a swimming hole or a skating rink. In 1942, the Hooker chemical company began using the canal to dispose of a witches’ brew of some “22,000 tons of drummed and liquid chemical wastes,” according to the E.P.A.’s most recent study of the site.

The manner of disposal, which continued until 1953, was sometimes haphazard, with some barrels punctured and seeping poison into the soil and groundwater. Still, the true extent of the pollution might never have come to light had the Niagara Falls Board of Education not purchased the property for $1 and decided to build a new elementary school there, on 99th Street, which drew newcomers to the area.

Complaints about strange odors and chemical residues began as early as the 1960s, and percolated in late 1976 and early 1977 after wet weather caused chemicals to seep into basements. Reports of rocks bursting into flame were already spreading among local children as troubling accounts of mystery illnesses, miscarriages and birth defects grew.

Those dangers were readily apparent to people like Kathy Murphy, 57, who still remembers the day her friend fell into a vat of chemicals near the 99th Street School while they were out walking.

“She walked first and she went right down in a barrel,” Ms. Murphy recalled. “I had to pull her out of this barrel. It was that close to the top because all the erosion.”

Ms. Murphy, who lived in a development to the west of the canal, said her father moved her family out of the neighborhood in 1977 out of concern for their safety.

She recalled her father pleading with local authorities: “He would go in the basement and there was this sludge that would come up in the drain, and he’d put it in a jar and he’d take it over and he’d show them, and say, ‘This is not sewage.’ It was nasty.”

Keith O’Brien, a journalist and the author of “Paradise Falls,” a 2022 history of Love Canal, noted that many of those who first moved into the Love Canal neighborhood were middle-class families, drawn to the affordable homes and good schools, who were mostly unaware of the place’s history.

“What’s sad to me,” he said, “is that it sounds like the same thing might be happening still today.”

There are few official markers of the area’s history, though its fence has a warning to trespassers. Near another demolished school, a stone monument bears a list of major dates in the crisis, ending in 2002, a smudged slab hidden behind a narrow palisade of firs, near a collection of Little League fields.

Randy Garrow, 55, still lives adjacent to the fence, though on the western side. His family refused to move back at the time of evacuations, even as their neighbors left. He said he was surprised to learn there were still chemicals buried just beyond the chain link — “I assume once they dug it out of here and capped it over that they obviously took everything” — but remained confident he and his family were safe.

Likewise, for those living in the “nonresidential” area, there seems to be little concern about contamination. One new resident, a young woman who declined to give her name, said she and her husband had bought a home about two blocks from the canal site in 2020 and had no worries about safety, arguing that the previous tenant had lived to almost 100 years old.

She added that she and her husband had been informed of the Love Canal history in a disclosure form when they purchased. Another resident, Patti Fuller, said she’d also signed a disclosure as part of her rental.

A lifelong resident of the greater Niagara Falls area, Ms. Fuller said she’s had no health problems in the year that she’s lived adjacent to the site, and feels safe, even though she vividly remembers the evacuations and demolitions.

Ms. Fuller said she often saw wildlife wandering the cracked streets and that “if there were anything that toxic, you’d see dead animals everywhere.” The only thing she wouldn’t do is plant a garden.

Since being informed of the neighborhood’s history, Mr. Montgomery, 34, who sells cars for a living, said he had spent hours watching YouTube videos about Love Canal and searching online for more information.

Despite his initial concerns, Mr. Montgomery plans to stay a little longer, saying he likes “the peace and quiet.” He said his son’s doctor had suggested the new bouts of asthma might be caused by all the grass around his house; his girlfriend hasn’t seen a doctor about her headaches and nosebleeds, but is due in August.

Mr. Montgomery is still planning on moving out of the Niagara Falls area soon, but said he felt the presence of other neighbors, scattered about these mostly ghostly streets, gave him some comfort.

“I kind of had to weigh out all the factors,” he said. “But, you know, everybody out here, they seem to be doing fine.”

Lauren Petracca contributed reporting.