Microbial Volatile Organic Compounds As Indoor Air Pollutants Term Paper

Excerpt from Term Paper :

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…

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