JEFFERSON CITY, Mo. - Smoke wafting from wood fires has long provided a familiar winter smell in many parts of the country - and, in some cases, a foggy haze that has filled people's lungs with fine particles that can cause coughing and wheezing.

Citing health concerns, the Environmental Protection Agency now is pressing ahead with regulations to significantly limit the pollution from newly manufactured residential wood heaters. But some of the states with the most wood smoke are refusing to go along, claiming that the EPA's new rules could leave low-income residents in the cold.

Missouri and Michigan already have barred their environmental agencies from enforcing the EPA standards. Similar measures recently passed Virginia's legislature and are pending in at least three other states, even though residents in some places say the rules don't do enough to clear the air.

It's been a harsh winter for many people, particularly those in regions repeatedly battered by snow. And the EPA's new rules are stoking fears that some residents won't be able to afford new stoves when their older models give out.

"People have been burning wood since the beginning of recorded time," said Phillip Todd, 59, who uses a wood-fired furnace to heat his home in Holts Summit. "They're trying to regulate it out of existence, I believe, and they really have no concern about the economic consequences or the hardship it's going to cause."

Others contend the real hardship has fallen on neighbors forced to breathe the smoke from winter wood fires.

The EPA typically relies on states to carry out its air quality standards. But states may not be able to effectively thwart the wood-burning rules, because federal regulators could step in to do the job if local officials don't.

"If the EPA wants to come in here and enforce it, come on in. (But) I'm not going to help them," said Michigan state Sen. Tom Casperson, whose law barring state enforcement of the EPA regulations takes effect March 31.

About 10 percent of U.S. households burn wood, and the number relying on it as their primary heating source rose by nearly a third from 2005 to 2012, the latest year for which federal figures were available.

The EPA's new rules, which are to be phased in over five years, apply only to new wood heaters and won't force anyone to get rid of their older models.

The EPA estimates the restrictions will reduce fine particle emissions from wood heaters by nearly 70 percent. It says that will result in an average of one fewer premature death per day and yield about $100 of public health benefits for every $1 of additional cost to manufacturers.

The rules mark the first update since 1988 for indoor wood stoves, which include both free-standing models and ones that fit inside traditional fireplaces. The EPA also is imposing its first-ever emission mandates on wood-fired furnaces and outdoor boilers, which use fire to heat water that is circulated through pipes to warm homes.

Nine states and dozens of communities already had required cleaner emissions for outdoor wood-fired boilers before the EPA acted, according to the Hearth, Patio & Barbecue Association.

The states objecting to the EPA's standards include some of the biggest wood burners. Michigan ranked tops nationally in fine particle emissions from residential wood burning in 2011, the latest year covered by EPA statistics. Missouri and Virginia both ranked in the top 15. Bills to bar enforcement of the EPA regulations also are pending in Wisconsin and Minnesota, which ranked second and third, as well as in West Virginia.

Disputes over wood heaters have sparked intense emotions- and legal battles - among neighbors. In late January, for example, an Indiana judge rejected a request from Mable and Gary Bowling for a preliminary injunction forcing one of their Rush County neighbors to stop using an outdoor furnace. The Bowlings claimed the smoke was unhealthy; the neighbors claimed the Bowlings had harassed them by repeatedly contacting police or firefighters.

Mable Bowling contends the wood smoke has worsened her asthma and led to other respiratory problems.

"What we're breathing is slowly killing us," Bowling, 61, said during a telephone interview occasionally interrupted by coughs.

The federal Centers for Disease Control and Prevention says fine particle pollution from burnt wood can get deep into people's lungs, causing breathing troubles.

But burning wood can be cheaper for some rural residents than heating their homes with propane, oil or electricity.

Many of the largest manufacturers' products meet the initial EPA requirements, but complying with the later phased-in rules could be more challenging. Manufacturers say some smaller companies may simply shut down.

Some critics of wood-fired heaters believe the EPA's rules don't go far enough. They note that in real-world use, the heaters often expel more pollution than in laboratory tests.

The hearth association estimates that two-thirds of the free-standing wood stoves currently in homes are more than 20 years old and may be greatly exceed emission standards.

"People hang on to their old wood stoves forever, and that's a problem," said Ed Miller, the senior vice president for public policy at the American Lung Association of the Northeast. "The key is there needs to be kind of a motivating factor to get you to give up the old stove."