Dangerous beauty: spore cases of aspergillus under a scanning electron microscope
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There's a love-hate relationship between human beings and mold. Roquefort cheese and fine salami owe their incomparable taste to specific mold cultures, but mold colonies that proliferate on walls can be a health hazard. A culture medium produced by Heipha, a EMD subsidiary, makes it possible to see and identify different types of mold.
The symbol of their triumph is a grayish-greenish-black spot that shows up on the wall, under a windowsill or in a corner of the shower. It's a reliable indication that the battle between human beings and molds has been won by the latter. This battle is being waged fiercely every single day — even though we're not always aware of it and therefore sometimes carelessly abandon the field of battle to the molds.
"By the time you see the mold, a lot has already happened," says Hermann Walterbusch, a building biologist who works at Wartig Nord GmbH in Hamburg, an assessment and engineering company that investigates moisture damage and plans renovation processes. "At that point, the individual mold fibers, which are invisible to the naked eye, have already proliferated and formed a network that contains between hundreds of thousands and millions of spores, most of which are colored."
Mold in an apartment doesn't look pretty, but the actual problem is related to health. The mold species that are most often encountered in the home are aspergillus, penicillium, and cladosporium.
“If you can see mold, it has already developed substantially.“
at Wartig Nord GmbH, Hamburg
They can cause serious harm to human health through the components of their cells, toxic products of their metabolism (mycotoxins), and their spores. The worst of these hazards include allergies and respiratory illnesses involving irritation of the conjunctiva, nose, and throat; coughing; headaches; and fatigue.
According to the Robert Koch Institute in Berlin, between three and ten percent of Germans suffer from allergies caused by molds. In most cases, the allergy began when the person breathed in mold spores. "We estimate that up to 40 percent of private homes are affected by mold, which in some cases is growing in concealed locations," explains Frank Bartram, a specialist in environmental medicine.
However, the connection between allergy complaints and the presence of mold is not clearly demonstrable, because there are still no scientifically proven conclusions regarding which concentrations of which types of mold cause which complaints. "Some people can tolerate molds and their emissions, whereas others can't," says Bartram.
Sometimes, the culprits are not very easy to identify, because at the moment there are industrially produced test extracts for only six of the approximately 80 species of mold that occur in interior spaces. A simple and practical process that was developed at the Institute for Toxicology at the University of Kiel, Germany, makes it possible to cultivate molds in culture media based on malt extract agar and then to produce extracts from these cultures.
If these extracts cause immunological reactions when combined with a patient's blood, there's only one solution to the problem: The mold that has become a health hazard must be removed. But even if no health problems have occurred, mold in general does not belong in the home.
In the laboratory, molds are cultivated in culture media for immunological tests
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All the same, there's no such thing as a home that's entirely free of molds. That's because molds have an important function in the natural scheme of things. They break down organic substances and release the resulting carbon into the atmosphere in the form of carbon dioxide. Without molds, the entire ecosystem would grind to a halt. That's why they need to be everywhere. The slightest breeze carries them into every corner, where they wait for the opportunity to multiply. Two conditions are essential if that is to happen: the presence of organic material and water. Molds find sufficient nutrition in dust, wood chip wallpaper, plaster cartons, and cardboard.
But the relative humidity has to reach 40 percent before the enzymes that help to decompose organic molecules such as cellulose are activated. Molds feel especially comfortable at a relative humidity of 85 to 90 percent in temperatures between 20 and 40°C. If the humidity continues for several days, an "ecosystem" develops on the wall. As Hermann Walterbusch explains, "The system is always in a state of motion. If the external conditions change, other types of mold settle in. That's why a sample taken of a spot of mold is always only a snapshot." That's also true of every petri dish that Walterbusch takes out of the incubator. Thick gray puffs, cottony white threads, and shiny bright-red spots of color on the culture medium produced by Heipha — all that can be found on a wall full of mold spots.
The solution seems easy: If there's no water, there won't be any mold. However, it's not so easy to put this principle into practice. In a four-person household, 12 liters of steam are generated every day — for example, from breathing, showering, and cooking. This dampness can no longer escape from the home, especially from well-insulated modern houses and apartments with well-sealed windows. It must be regularly removed from the dwelling by means of thorough airing; otherwise, it condenses in the cooler areas.
Such areas include poorly insulated walls and "heat bridges" around doors and windows — in other words, places with inadequate insulation. That's where molds like to live. To air rooms properly, it’s necessary to air them in bursts, i.e. by opening the windows entirely for several minutes several times a day. The best method is cross-ventilation which means opening windows on opposite sides of a room or apartment so that significant air movement is generated.
The popular method of simply tilting the windows does not ensure a sufficient supply of fresh air; the walls simply cool down. Even more effective than active airing is a series of airholes in the windows that open automatically when the humidity is relatively high. According to the building biologist Hermann Walterbusch, "The future belongs to technically controlled basic ventilation that doesn't have to be actively managed by the apartment residents." All the same, even with such technical support, at times of maximum humidity — such as after cooking or taking a shower — the rooms will still require a good airing.
Like clothes for people, paints smarten up objects, protect them from the elements, and are subject to fashion.