NEW YORK (AP) -- Few sights capture Manhattan's beauty like the grand, old apartment buildings that ring Central Park. But for decades, many of these mansions for the rich and famous have also been a literal source of urban grit.
Like other pre-war buildings throughout the city, scores of the graceful towers around the park have long burned the dirtiest heating fuel around: a nasty sludge called No. 6 oil that puts more soot into the air annually than all the city's vehicles combined.
This is the kind of Dickensian pollution you don't need fancy equipment to see. On winter mornings, the chimneys of buildings using No. 6 oil, or its nearly-as-bad cousin, No. 4, will sometimes spew thick black smoke.
But that has begun to change as a result of new city regulations put in place in 2011. Since then, around 1,500 city buildings have switched to cleaner fuels. Changes are under way at many more, including some of those Central Park icons.
Late last month, The Dakota, famous as the home of John Lennon and Yoko Ono (and Lauren Bacall, and Connie Chung, and past residents like Leonard Bernstein and John Madden, and too many other luminaries to list), applied for construction permits to begin installing a new dual fuel boiler system that can run on either cleaner-burning No. 2 oil, or even-cleaner natural gas.
Similar conversions are under way at several of the Dakota's close neighbors along Central Park West, including the equally luxurious San Remo, where apartment owners in recent years have included Bono, Steve Martin, Dustin Hoffman and Steven Spielberg.
The changeovers are happening to the delight of environmentalists like Isabelle Silverman, an attorney at the Environmental Defense Fund.
"It doesn't make sense to pollute the air right where you live," she said, adding that her own building had also recently made the switch.
New York still has a long way to go. When Mayor Michael Bloomberg rolled out regulations curbing use of the heaviest fuel oils in 2011, 10,000 buildings in the city still used No. 6 or No. 4 oil. That makes up just 1 percent of the city's buildings, but a collective 85 percent of the soot pollution from heating furnaces, city officials said.
The rules adopted by the city two Aprils ago require buildings to stop using No. 6 oil by 2015. For a time, people will still be allowed to burn No. 4 heating oil in their old furnaces, but any newly installed boiler will have to use natural gas, low-sulfur No. 2 oil, or another low-emission fuel such as biodiesel. The use of No. 4 oil will be banned, even in older furnaces, by 2030.
City officials have predicted that the phase out of the old fuels will lead to substantial air quality improvements, which in turn will reduce the number of hospitalizations and emergency room visits for people with asthma, or other heart and lung conditions.
"It will save lives," Silverman said.
No. 6 oil is something of a New York phenomenon. A cheap residual grade of oil, it never caught on as a residential heating fuel elsewhere in the U.S., partly because it is so sooty, only very large apartment buildings can afford the maintenance staff needed to keep equipment clean and functioning.
Switching to No. 4 oil is relatively simple. A conversion to No. 2 oil can be more costly. A switch to gas — now both the cheapest and cleanest fuel widely available — can involve pricey overhauls to a building, and sometimes street work to connect to neighborhood gas mains.
The San Remo's contractors estimated in their construction application that just the interior work there would cost $210,000.
Connecting buildings to gas lines can cost tens of thousands of dollars more, or even $1 million if the nearest main is blocks away. But Con Edison and other natural gas providers have been waiving many fees if clusters of buildings sign on together.
To help less-wealthy buildings make the switch, city officials and private banks put together a $100 million loan program.
And natural gas is so cheap right now, many buildings may be able to recoup their conversion costs in just a few years.
Hess, a leading oil provider in New York that also has an energy management business, said converting one huge apartment complex in Brooklyn to gas cost $3.8 million. But that change, the company said, will slash 30 percent from the complex's annual heating bill within five years. The complex, called Lindsay Park, was burning 1.6 million gallons of No. 6 oil annually, the company said.
Gas, of course, has issues of its own.
One of the reasons it is so cheap right now is because vast quantities are being extracted by a drilling technique known as fracking, which involves injecting huge volumes of chemical-tainted water underground.
Among the environmentalists who have protested fracking: The Dakota's own Yoko Ono. She and son Sean Lennon founded a group called Artists Against Fracking last August, about the time buildings on her stretch of Central Park West began converting to gas heat.
Ono declined to comment through a publicist for the group.