*these proceedings used with permission from Western Veterinary Conference 2007.

The Occupational Safety and Health Administration (OSHA) estimates that 69,000 people reporting severe headaches and 105,000 people reporting respiratory problems in the workplace may be suffering from poor indoor environmental quality. Similar environmental quality problems exist in homes, possibly at a more severe degree. The impact of these indoor home conditions on the small companion animal population is unknown. However, it is reasonable to hypothesize that the impact may be greater in that group than in their human counterparts, particularly in view of the fact that many animals never leave the indoor environment in which they live and may come into closer contact with specific sources such as contaminated carpeting or pesticides.

The goal of this lecture is to familiarize the veterinary practitioner with the conditions and issues involved in indoor environmental quality problems. The magnitude of the problem in human medicine has not yet been fully elucidated, and the field has been practically unaddressed by the veterinary community.

Changing energy use strategies in the 1970s resulted in construction of buildings with improved energy efficiency and tighter sealing to prevent energy loss. As a consequence, human health complaints relating to indoor environments began to increase, and the terms tight building syndrome and sick building syndrome were adopted to describe this problem. Complaints relating to the environment had previously been attributed to either poor working conditions or psychological factors. It soon became apparent, however, that health complaints could also be attributed to inadequate ventilation, mold overgrowth, lack of fresh air exchange, excess biologic and chemical contaminants, and dampness or inadequate dilution of indoor contaminants. Increased incidences of allergic diseases, coughing, wheezing, shortness of breath, asthma, bronchitis, headaches, eye irritation, muscle aches, fever, chills, nausea, vomiting, and diarrhea are reported among children and adults exposed to indoor biologic contaminants; these substances encompass a wide array of contaminants and biochemical byproducts.

A dynamic mixture of chemical, biologic, and particulate pollutants arising from a variety of sources circulates in indoor air. These pollutants are influenced by air movement, ventilation, temperature, and humidity. Most of the chemical sources of indoor contaminants are volatile organic chemicals (VOCs). Analyses of indoor air samples have demonstrated that between 50 and 300 different volatile organic chemicals can be present at low levels in nonindustrial environments such as offices, homes, shopping centers, and malls.

Biologic sources of indoor pollution include mold, fungus, pollen, spores, bacteria, viruses, and insects, such as dust mites and roaches. Relatively high levels of humidity and moisture allow biologic agents to increase to levels that, when disseminated indoors, can trigger illness and allergies. High relative humidity also encourages growth of the dust mite population, which can cause allergies and asthma. More attention is being focused on biochemical products of microorganisms as potential causes of indoor-related respiratory illness. These include endotoxin, 1,3-beta-glucan, mycotoxins, peptidoglycan, and volatile organic chemicals emitted from fungi.

Physical factors, the third source of indoor-related illness, include dusts, fibers, particulates, and overall comfort factors such as ventilation, lighting, temperature, humidity, noise, and vibration. Dust and particulate matter are always present indoors. Each cubic meter of air contains small concentrations of millions of particulates, of which 99% are invisible to the eye.

Building Materials and Furnishings

Products used in construction contain chemicals that can off gas into the indoor environment. Emissions of volatile organic chemicals from building materials depend on the nature of the material, the chemicals involved, and the location of the material in the structure. Such products include wood, insulation, plastics, sealers, caulking, adhesives, paints, varnishes, waxes, finishes, lacquers, fabrics, and carpets.

Wood furnishings purchased for use in homes are rarely solid wood anymore; rather, they may have a wood facing on a product mainly composed of particleboard or plywood. Formaldehyde and other contaminants that are "outgassing" from these products into energy-efficient "tight" homes can result in significantly elevated indoor air exposures.

Furnishings and fabrics can act as "sinks" that absorb airborne chemicals, releasing them slowly back into the indoor environment depending on temperature, humidity, and ventilation. In general, warmer temperatures and higher humidity increase the rate of emission of volatile organic chemicals.