Microbial Volatile Organic Compounds as Indoor Air Pollutants

Air pollution pertains to substances and gases in the air that threaten health and life. Among these are pollutants and irritants, such as nitrogen oxides, sulfur dioxide, and carbon dioxide; particulates, volatile organic compounds (VOCs), toxic substances and some natural substances, like pollen. But most of the pollution comes from the by-products of industrialization - fossil fuel combustion, transportation, transportation, power plant emissions and those from other industrial processes. The burning of fossil fuels to generate electricity alone is the greatest source of air pollution in the U.S.A. These outdoor pollutants can undermine health and cause environmental disturbances, such as acid rain, and are toxic.

Studies show that we now spend more than 90% of our lives inside buildings and other constructed environments. Because of this, such structures - including homes and office buildings - are constructed with energy efficiency and comfort foremost in mind. The installation of central heating, cooling systems, the reduction of heat to the minimum and air-tightness has been the standard practice (Heimlich). Through the years, this practice and trends have led to the use of complex materials for furniture, fabrics, cleaners, detergents, detergents and preservatives, as well as to foreign proteins, dust, and gases.

The 1976 outbreak of the Legionnaire's Disease in a hotel in Philadelphia sounded the alarm when 182 pneumonia cases and 29 deaths from a still-unknown bacterium at the time (later called Legionella pneumophilia) were reported. Investigations led to the ventilation and humidification system of the hotel, which in turn, resulted in the recognition of an epidemic of illnesses connected with building conditions.

Since then, health workers began to receive increasing numbers of complaints of headaches and allergic reactions to some unknown stimuli. The reactions included lethargy, fatigue, dizziness, nausea, irritation of the mucous membrane, irritation of the eyes or nose and pharynx and sensitivity to odors. It was discovered, after many years of investigation, that these reactions occurred when those affected were inside certain buildings and disappeared when they left those buildings. These specific and non-specific complaints, when were linked to a particular building, therefore, came to be known as the "sick building syndrome." More importantly, it has been noted that one type alone of indoor pollutants - volatile organic compounds or VOCs -- can make indoor air 10 times more hazardous than outdoor air. This must be realized with the fact that virtually all American children aged 6 and older are in school and younger ones in day-care, more than 50% of adult workers in North America alone and Western Europe are in engaged in white-collar jobs" and working all day long in indoor office settings. And retirees are likewise indoors (Oliver and Shackleton).

Indoor sources of contamination that make up the syndrome have been classified into major combustion pollutants (carbon monoxide, nitrogen dioxide and sulfur dioxide), biological air pollutants (among them, molds, dust mites and dander), VOCs (gases like formaldehyde, pesticides, solves, cleaning agents, benzene and perchloroethyllene) and heavy metals (lead and mercury, although these have been on the wane recently).

Symptoms involved in the "sick building syndrome" are many and varied, as well as affecting many of the body's systems. Physical and laboratory findings were inconclusive, but these were resolved upon leaving the building and reoccurred with reentry. It took much time before management and medical personnel could identify the problem and the cause. Many factors were occurring at the same time. In the meantime, common complaints observed by the National Institute for Occupational Safety and Health in investigating 529 buildings were listed as "eye irritation, dry throat, headache, fatigue, sinus congestion, skin irritation, shortness of breath, cough, dizziness, nausea, sneezing and nasal irritation (Oliver and Shackleton).

II. MVOCs as Indoor Pollutants and Their Impact on Human Beings.

It was in the last two decades when the significance of indoor air pollution was winning recognition along with asthma as a serious health hazard that a connection was established. Risks for asthma were identified as to include indoor air contaminants, such as house dust mites, cockroach allergens, molds, other fungi and tobacco smoke. Asthma cases kept increasing and particularly disturbing in children and young adults. Both self-reported and asthma-related hospital admissions increased. Hospitalization with asthma as the principal diagnosis went up from 1979 to 1994, conditioned by age and gender.

Investigations in the last decade pointed to microorganisms as the primary sources of indoor air contaminations, accounting for 35-50% of all indoor air quality cases reported. Three or two decades earlier, microorganisms were found to the cause of only 5% of the cases and the vast majority were attributed to airborne contaminants like asbestos and coal dust. (McNeel and Kreutzer) This change was believed to a shift from the use of chemical contaminant-based investigations to an approach that combined physical, chemical and microbiological elements of indoor air environments.

Fungi are the organisms of specific and greatest significance, because they constitute around 25% of the earth's biomass (McMeel and Kreutzer).and because one type of fungi - molds - has been identified as a common cause of indoor contamination. (The other types are yeasts, mushrooms and mildew..) Depending on the mold species, its metabolic products, the amount and duration of person's exposure and susceptibility, the effect of molds on human health can be allergy, infection, irritation of the mucous membrane and sensory, or toxicity (Amman).

A person affected usually develops an allergy if he or she is genetically capable of the response (atopic). The allergic reaction can be mild, passing, severe or chronic. The Institute of Medicine pointed to allergic rhinitis as the most common chronic disease: 14% suffers from allergy-related sinusitis; 10-12%, from allergy-related asthma; 9%, from allergic dermatitis; and less than 1%, from serious chronic allergic diseases, such as allergic bronchopulmonary aspergillosis and hypersensitivity pneumonitis. Molds are only one of the many sources of indoor allergens, besides house dust mites, cockroaches, and pets' wastes.

Infection from molds is not frequent, except when a person is susceptible due to immune compromise from disease or treatment (Amman). The infecting mold is the Aspergillus fumigatus and the disease is called aspergilloses. It affects the skin, eyes, the lung or other organs or systems.

Some fungi produce volatile compounds through primary or secondary metabolism, which are released indoors. When inhaled in sufficient concentration, they can irritate the mucous membranes of the eyes and the respiratory system (Amman). Some of the compounds - alcohols or aldehydes and acidic molecules -- are produced continually during primary metabolic processes, when the fungus consumes energy source. The fungus can metabolize with or without oxygen (aerobically or an-aerobically), and while it grows, it can produce strong or unpleasant odors and very poisonous gases - example, arsine from arsenic contents of wallpapers -- from the substrate on which it grows. On the other hand, fungi do not always produce secondary metabolites because they need extra energy. The compounds produced have the familiar moldy or musty smell.

These fungal volatile compounds also irritate the trigeminal nerve, which is sensitive to pungent smells precisely by avoiding the stimuli (Amman). Besides avoidance, the stimuli produce breath-holding, discomfort, and strange sensations, like itching, burning and skin crawling. The reaction further results in decreased attention, disorientation, reduced reflex time, dizziness and other effects (Amman). At higher exposure levels, these VOCs can affect the central nervous system itself.

Molds can also produce mycotoxins, secondary metabolites, which are almost entirely poisonous: they interfere with cellular processes such as the synthesis of RNA and DNA. Many species of molds produce mycotoxins, like some found in "sick" buildings. Health sectors have grown apprehensive towards the effects of over-exposure to multiple mycotoxins from mixed mold spores growing in wet indoor environments. (Amman).These are cytotoxic (or toxic to the cell) and, therefore, can damage the gut, the king or the lung, the physical defense mechanisms of the respiratory tract, reduce the body's natural ability to clear the air passages of contaminants. They can also damage alveolar macrophages that protect the deeper lungs from contaminants. These mycotoxins likewise increase the susceptibility to other infectious diseases and reduce the body's natural defenses (Amman).

Exposure to mycotoxins of molds indoors can result in: more fragile veins, tissue hemorrhage (vascular system); diarrhea, vomiting, intestinal hemorrhage, liver necrosis or fibrosis (digestive system); respiratory distress and bleeding from the lungs (respiratory system); tremors, incoordination, depression and headache (nervous system); rash, burning sensation, photosensitization (cutaneous system); nephrotoxicity (urinary system); infertility and change in reproductive cycles (reproductive system); and changes or suppression of the immune system and the presence of many mycotoxins.

III. Analysis Techniques. Sampling has been difficult and limited, because:

1. only a few experiments on mycotoxins have been performed in the process of being inhaled, which in turn is the most probable way of exposure indoors. The body defenses observed during ingestion are different from those during inhalation, and evidence points to inhalation as the way to more serious responses to the toxins;

2. there are hardly any studies done on the effects from low-level or chronically low-level exposures or ingestion of mycotoxins. Only the effects of high-level, acute, sub-acute and sub-chronic ingestions to single mycotoxins have been studied. All we have on other mycotoxins are information on their toxicity or their laboratory effects;

3. The effects of multiple exposures to mycotoxins in the air and those of other breathed indoor air pollutants are still unknown;

4. effects of other biologically active molecules that produce allergic reactions, such as irritation and acting with mycotoxins are similarly unknown. The measurement of spores and their fragments also varies, and comparison of results is still not possible with current equipment and machines;

5. many mycotoxins may be measurable as environment samples, but not in human or animal tissues. This leads us to rely on circumstantial evidence for exposure measurements, such as the presence of the contamination in the person's environment, discovery of spores in the air, symptoms and experimental lesions caused by mycotoxins, just to be able to establish an association with an illness;

6. The responses of those exposed indoors to complex aerosols are variable, accordint to age, gender, health conditions, genetic make-up and degree of exposure;

7. contaminations in buildings also varies greatly and depends on the location of the organisms and the route of exposure. Mere presence in a building does not always constitute exposure; and 8. investigations of environments usually happen after the afflicted persons have gotten ill and do not always reflect the conditions when the development of the illness occurred.

Unlike exposures to chemicals, those with active microbial growth cannot be recreated (Amman). Indoor environments are dynamic ecosystems (Amman), which are altered by changes in moisture, temperature, food sources and the presence of other growing microorganisms in it. The production of toxins also changes with the age of cultures, the stage of spore development, the availability of nutrients, moisture, and the presence of organisms that compete. Measurements of the environment after the contamination can only and always yield only an estimate of the conditions during the exposure when the illness started. It is only when the invading organisms and their products are present - along with a knowledge of lesions and the effects of these toxins - can there be a clear link between the contaminants and the illness.

Methods for analyzing indoor air VOCs require certain criteria in order to increase the reliability of indoor measurements. These criteria are:

a) capability to detect pollutants at ppt and ppb levels;

b) easy-to-use collection devices c) samples of pollutants that can be accurately analyzed and reproduced;

d) a minimum of contamination possibilities e) sampling periods must be compatible with monitoring requirements

IV. Growth and Metabolism. Moisture of the common ventilation system can allow fungi, especially molds, and bacteria to breed and multiply. When they do, they can cause respiratory irritation, skin problems, the onset or worsening of allergies, fatigue, headaches and asthma in those who breathe the air from such ventilation system. The American Lung Association noted that asthmatics have increased by 59% since 1970. Asthma has been observed to result from overexposure to molds; dampness in carpets or within walls; water, pipe or roof leaks, which can all produce mold spores, long after the leaks have been repaired.

Molds consist of a chain of cells called hyphae, which branch out and intertwine to form the body of the fungus (mycelium) (McNeel and Kreutzer). All the fungal cell walls have the beta-D- glucan, which is a glucose polymer with immunosuppressive mitogenic and inflammatory qualities. This element seems to cooperate with bacterial toxins to cause the airway to get inflamed after inhalation.

Many poisonous molds have been discovered during investigations of indoor air quality in many countries, and the most frequently found genera or species of molds are the aspergillus, penicillium, and the stachybortys.

The penicillium species abounds indoors, even in clean places, although they flourish mostly in problem or "sick" buildings. Its spores have the highest concentrations of mycotoxins, so that these remain viable even when the spores are dead. Among the important poisons or toxins produced by this species are nephrotoxic citrinin and nephrotoxic ochratoxin.

The aspergillus species are also commonly found in problem buildings. It produces many likewise poisonous species, the most important being A.. parasiticus, A. flavius, and A. fumigatus. The first two produce aflatoxins, which are fatal to the liver, brain, kidneys and the hert. Repeated exposures can lead to cancer of the liver. Symptoms of aflatoxicosis are fever, vomiting, coma and convulsions (Amman). The species A. flavus is found indoors in tropic areas, sometimes in flowerpots. A. fumigatus also abounds in many indoors. Another species, the A. versicolor, was also found in wallpaper, wooden floors, fiberboard and other suchlike building materials

Species stachybotrys chartarum (atra) has sticky molds when wet and is not cultured in standard media (Amman). Unlike other species, it is unable to compete with other spores and may be killed by these, but it is no less poisonous when inhaled. It requires a high moisture level and grows fast in the presence of moisture in roof or wall leaks, especially in plumbing leaks, which are always damp or wet. The point is that is often concealed in walls and other hidden spaces, where it often grows abundantly. And because it requires very little nitrogen, it can grow on wet hay and straw, paper, wallpaper, ceiling tiles, carpets, (cellulose-based) insulation materials and filter paper. It causes lesions on the skin and the gastrointestinal tract and obstructs blood cell formation. A person who handles any of these contaminated materials will often show symptoms like cough, rhinitis, burning sensations of the mouth and the nose, skin irritation, especially in parts that sweat. The toxins of this species, called macrocyclic trichothecenes, have been described as killing thousands of horses in Russia and the Ukraine and as infecting an entire family, living in a house with a leaky room. The symptoms ranged from diarrhea, fatigue, dermatitis, general malaise, and psychological depression. Other reports describe the fatal and near fatal results of exposure to the species.

Consider, too, that schools have their own conditions that open them to sources of contaminants, including fungi, in addition to vapors and fumes from laboratories, wood-working shops and art classrooms. Children also have the characteristic habit of encouraging the spread of infection, such as coughing and sneezing without protection. They are also less likely to wash their hands and likelier to share infected or contaminated pencils and other school things.

Compounding the problem is the fact that outdoor air contamination can aggravate indoor air pollution problems. Outdoor environmental pollutants can and do become part of indoor - and these include pesticides, vehicular exhaust, such as diesel exhaust from trucks at commercial building docks, and tobacco smoke from smokers standing at building entrances and exits.

V. Cnclusion: What Can Be Done

Authorities and experts do not see the problem of poor indoor quality and its harmful effects on people if no massive, effective and consistent is action is taken at present. Various approaches can be applied. Employees who suspect that their building is making them sick should take note of their reactions and observe of these disappear when the leave the building and re-appear when they re-enter it. They can also examine the buildings for things they can control, like opening windows or doors to improve air circulation. They can also limit temperature changes, limit the use of colognes, perfumes, soaps, shampoos, deodorants, detergents and air fresheners. And if these employees are convinced that the building is sick, they can collect evidence from other occupants and meet with a health care worker or the building owner and the local health officer regarding the problem.

It may take time and other conditions to effectively eliminate moisture sources, but in the meantime, air conditioners and dehumidifiers can help control humidity (McNeel and Kreutzer) and water collection traps should be cleaned as a routine to discourage microbial growth. A chlorine bleach solution can remove visible molds, as well.

Moisture control is clearly the answer to the control of molds indoors. Dry any leaks or spills quickly within 24 to 48 hours to discourage the growth of molds. Roof gutters should be regularly cleaned and repaired. The ground should slope away from the building foundation so that water will not enter or remain in the foundation. There should be no obstructions to the air-conditioning drain lines so as to flow properly. Indoor humidity should remain low. Dry the wet surface of windows, walls or pipes with moisture.

When you smell something musty or moldy, investigate. Many molds are hidden behind dry wall, wallpaper or panel, carpet underside, pipes and furniture. Caution should be taken if the investigation requires removing a wallpaper which will release spores on the paper's underside. Use biocides to kill molds sparingly or with expert advice. If the moisture problem is solved, there will be no need to sterilize the area. But if the use of disinfectants or biocides is the choice or decision, the area should always be ventilated and the air exhausted outdoor. Chlorine bleach solution should not be mixed with other cleaning solutions or detergents containing ammonia: toxic fumes are likely products.