NEW YORK, USA (AP) — A month after Sandy’s floodwaters swept up his block, punched a hole in his foundation and inundated his furnace, John Frawley still has no electricity or heat in his dilapidated home on the Rockaway seashore in New York.

The 57-year-old, who also lost his car and all his winter clothes in the flood, now spends his nights shivering in a pair of donated snow pants, worrying whether the cold might make his chronic heart condition worse.

“I’ve been coughing like crazy,” said Frawley, a former commercial fisherman disabled by a spine injury. He said his family doesn’t have the money to pay for even basic repairs. So far, he has avoided going to a shelter, saying he’d rather sleep in his own home.

“But I’m telling you, I can’t stay here much longer,” he said.

City officials estimate at least 12,000 New Yorkers are trying to survive in unheated, flood-damaged homes, despite warnings that dropping temperatures could pose a health risk.

The chill is only one of the potential environmental hazards that experts say might endanger people trying to resume their lives in the vast New York and New Jersey disaster zone.

Uncounted numbers of families have returned to coastal homes that are contaminated with mold, which can aggravate allergies and leave people perpetually wheezing. Others have been sleeping in houses filled with construction dust, as workers have ripped out walls and flooring. That dust can sometimes trigger asthma.

But it is the approaching winter that has some public health officials worried most. Night-time temperatures have been around freezing and stand to drop in the coming weeks.

New York City’s health department said the number of people visiting hospital emergency rooms for cold-related problems has already doubled this November, compared with previous years. Those statistics are likely only the proverbial tip of the iceberg.

Mortality rates for the elderly and chronically ill rise when people live for extended periods in unheated apartments, even when the temperature is still above freezing, said the city’s health commissioner, Dr Thomas Farley.

“As the temperatures get colder, the risk increases,” he said. “It is especially risky for the elderly. I really want to encourage people, if they don’t have heat in their apartment, to look elsewhere.”

Since the storm, the health department has been sending National Guard troops door to door, trying to persuade people to leave cold homes until their heating systems are fixed. The city is also carrying out a plan to spend hundreds of millions of dollars helping residents make emergency repairs needed to restore their heat and hot water.

Convincing people that they could be endangering themselves by staying until that work is complete, though, isn’t always easy.

For weeks, Eddie Saman, 57, slept on sheets of plywood in the frigid, ruined shell of his flooded bungalow on Staten Island. He stayed even as the house filled up with a disgusting mold that agitated his asthma so much that it sent him to the emergency room.

Volunteers eventually helped clean the place up somewhat and got Saman a mattress. But on Sunday the wood-burning stove he had been using for heat caught fire.

Melting materials in the ceiling burned his cheek. A neighbour who dashed into the house to look for Saman also suffered burns. The interior of the house — what was left of it after the flood — was destroyed.

Two days later, another fire broke out in a flood-damaged house across the street, also occupied by a resident trying to keep warm without a working furnace.

Asked why he hadn’t sought lodging elsewhere, Saman said he didn’t have family in the region and was rattled by the one night he spent in an emergency shelter. He said it seemed more populated by homeless drug addicts than displaced families.

“That place was not for me,” he said.

The Federal Emergency Management Agency offered to pay for a hotel, but Saman said he stopped looking because every inn within 100 miles (160 kilometres) of the city seemed to be booked solid through December.

Saman’s case may be extreme, but experts said it isn’t unusual for people to hurry back to homes not ready for habitation.

After Hurricane Katrina in 2005, medical researchers in New Orleans documented a rise in respiratory ailments among people living in neighbourhoods where buildings were being repaired.

The issue wasn’t just mold, which can cause problems for years if it isn’t dealt with properly, said Felicia Rabito, an epidemiologist at Tulane University’s School of Public Health and Tropical Medicine. There was simply so much work being done, families spent their days breathing the fine particles of sanded wood and drywall.

People complained of something that became known as the “Katrina cough”, and while it subsided once the dust settled, researchers later found high lead levels in some neighbourhoods due to work crews ignoring standards for lead paint removal.

A group of occupational health experts in New York City, including doctors who run programmes for people sickened by World Trade Centre dust after the September 11, 2001, terrorist attacks, warned last week that workers cleaning up Sandy’s wreckage need to protect themselves by suppressing dust with water, wearing masks and being aware of potential asbestos exposure.

“There are clearly sites that you don’t want children at… and it is very challenging for homeowners to know whether it is safe to go home,” said Dr Maida Galvez, a paediatrician and environmental health expert at The Mount Sinai Hospital who is part of a team evaluating hazards in the disaster zone.

US Rep Jerrold Nadler has urged FEMA and the Environmental Protection Agency to develop a testing programme that could give residents an indication of whether their homes were free of mold, sewage and other hazardous substances.

Farley, New York City’s health commissioner, said people entering rooms contaminated by floodwater should wear rubber boots and gloves, and exercise care in cleanup. The hazard posed by spilled sewage is a short-term one and experts say the disease-causing bacteria found in it can be wiped out with a good cleaning. But they say anything absorbent that touched tainted water, like curtains or rugs, should be thrown out.

As for the bitter cold, there was no test needed to tell John Frawley that his home is no place to be spending frigid autumn nights.

“A couple of days ago, I was shivering so badly, I just couldn’t stop,” he said.

Yet with winter nearly here, he still had no plan for getting his heat working again or his ruined electrical system restored, although he also has passed up some of the programmes designed to help people like him.

And he has no intention of heading to a shelter.