The havoc superstorm Sandy raised last month has proved a boon for some of the tiniest New Yorkers: Billions of mold spores floating through the air in search of water. Mold has found ample landing ground in storm-soaked homes, where they set up residence and grow into colonies.

Even in a building flooded that badly, a mold colony might just be an unsightly presence. But particularly among the allergy-prone and autoimmune, mold can easily turn into a major health issue for the human inhabitants it shares the air with.

“Mold” actually refers to thousands of different species of fungus that thrive in moisture and have a propensity for taking over organic material.

Penicillum. Photo: Wikimedia Commons

More than 400 of them are types of pencillium, a common indoor fungus that’s green in color — like the mold one often encounters growing on food. (A handful of penicillum species are fit for service in the antibiotic penicillin.)

In the wake of the storm, penicillum has been cropping up on wooden fixtures of homes saturated by floodwaters. Some species of penicillum can create chemicals called mycotoxins, which have the potential to provoke allergy and respiratory problems, especially in individuals already prone to those conditions.

Aspergillus fumigatus. Photo: Wikimedia Commons

Mycotoxins are a known product of aspergillus, which grows into dense colonies ranging from white or yellow to brown or black. This stubborn beast is particularly hardy — able to find water in mostly dry substances and withstand higher temperatures than other molds. Nasty traits for a fungus named after a brush used for sprinkling holy water. Like any type of mold, it can grow just about anywhere it finds moisture and fungus-friendly material, which includes most of what is used to make a house — from drywall to carpeting.

Cladosporium, olive green and velvety, is cropping up as well. This mold can trigger allergies, though it’s more likely to cause severe illness in plants rather than humans.

Stachybotrys chartarum. Photo: Cornell Fungi

If mold had a Most Wanted list, stachybotrys chartarum would top it. This is the infamous “black mold” — another source of mycotoxins — that has entered the public spotlight via a flurry of media reports and litigation centered on its alleged health effects. Lawsuits have sought to link it to “sick building syndrome” and ailments from allergies and headaches to more severe, neurological afflictions. The scientific community has not reached any consensus about these effects.

But whatever the mold species, the Institute of Medicine of the National Academies has found “sufficient evidence” to link exposure to respiratory problems, coughing, wheezing and asthma symptoms in susceptible individuals, as well as some evidence to suggest it can provoke respiratory illnesses in otherwise-healthy children.

The U.S. Centers for Disease Control and Prevention notes that it’s generally not necessary to identify the type of mold growing in a home or business — just to deal with it if you find it.

The type of mold that grows in a home depends on the type of spores in the air, which is affected by any range of factors — even down to something like the type of furniture you’ve had over the years, said Dr. Ginger Chew, a epidemiologist for the CDC.

The difference between the mold you might encounter in your bathroom and the mold that has besieged New York and New Jersey’s flooded coastal homes is largely a difference in scale: More water means more places for mold colonies to take over. It’s hard to predict exactly which of the many species will grow there and what types of health effects they could trigger, Chew said.

She added that people who are not affected by mold in their homes now could be vulnerable in the future if they develop a condition like an autoimmune disease, so it’s important to rid the area of mold growth to prevent future problems.

After a flood, the extent of mold growth is not always visible. “Cleaning just the mold you see might not be enough,” she said.

Bill Sothern, an industrial hygienist and founder of New York-based Microecologies, Inc., has been inspecting structures in downtown Manhattan, Breezy Point, the Rockaways and Long Island. He said that in flooded homes mold could very likely lurk inside walls — on the opposite side of Sheetrock and in insulation. For that reason, he recommends tearing out Sheetrock up to at least two feet above the watermark after flooding to find and deal with any growth.

Sothern advises that residents and volunteers who come across severe levels of mold should stop and get professional advice before proceeding with cleanup. He said he’s seen people using N95 respirators — face masks that filter out particles in the air — but cautions that they might not be enough to protect someone from mold spores that can start flying when disturbing affected walls.

The good news, if there is any, is that a month after the storm, flood areas are seeing much less mold than they could be. Salt in seawater helps inhibit its growth. At the same time, the cold weather that has driven so many people out of flooded homes is keeping mold populations down, too — unlike in New Orleans after Hurricane Katrina, where brackish waters and temperatures in the 80s left thousands of mold-riddled homes beyond repair.

Said Sothern: “Four weeks later, we still haven’t seen anything like Katrina.”