PARTICULATES consist of a great variety of materials that vary in size from sub-micron to grains of sand. This matter which is transferred through the air is often small enough to be inhaled deep into the lungs, yet large enough to remain lodged once they enter. The nose, throat, and lungs filter out particles that are 1.5 microns in size (a micron is one-millionth of a meter), while particles smaller than 0.1 micron are usually exhaled. Therefore, the particles with the greatest concern are 0.1 to 1.5 microns. Asbestos, paint chips containing lead, disease-causing dust, or a fungus that stimulates an allergic response can be a serious problem. Even insecticides or rodent control treatments can cause short-term (acute) or long-term (chronic) health problems to occupants of building facilities. These join the list of second-hand smoke, industrial process source pollutants, and irritating dirt and dust from the outdoors and generated indoors by human activity, as serious health impacting indoor pollutants.

GASES are generally referred to as volatile organic compounds (VOC's) and include a wide variety of solvents, formaldehyde, and many other manmade and natural materials. They also include carbon dioxide, oxygen, nitrogen, ammonia, metallic oxides such as nitrous oxides and sulfur oxides. Ozone from machinery and formaldehyde from building materials have been recognized as "major health impacting indoor pollutants" long before today's concerns about indoor pollution came about. Formaldehyde is the most common of all VOC's. Six billion pounds are produced in the United States each year and globally this is still a major component of adhesives and insulation materials. Health effects of formaldehyde and other VOC's mimic that of a cold. If the exposure is prolonged, the health effects generally get worse until the individual experiences such problems as chemical sensitivity, potential for an asthma attack, and other chronic health problems. Typically, indoor concentrations are 2 to 5 times higher indoors with some up to one hundred times higher.

BIOLOGICALS include various insects, mites, ticks, protozoans, bacteria, and fungi are what make up the biological category. This group also includes particulates and gases as well. Biologicals interact so dramatically, directly, and destructively with buildings and their inhabitants that they have earned the right to be called the most potent of all pollutants. Even more significant, is the fact that the biologicals can be tied to all of the human responses that we associate with "sick building syndrome." This is not true of the other pollutants. Non-biological pollutants, such as particulates or gases can stimulate specific human symptoms but not all of them. Besides the bacterial, fungal (mold, mildew, and yeast), and viral disease causing organisms, there are a number of these organisms that cause allergic response in sensitive individuals. Legionella bacteria, lung disease causing bacteria, E. coli, Salmonella species, and the typical skin bacteria such as Staphylococcus and Pseudomonas are all part of the biologicals found in buildings. Each of these organisms has specific life styles and habitats in buildings and are the reasons for the growing concern of occupants in today's buildings marketplace.

Particulates, gases, and biologicals represent the classes of pollutants that negatively affect people and materials in buildings. These groups are complex and are present in all areas throughout a building. The most potent of these pollutants are of course the biologicals. Knowing as much as we can about these classes, arms us with the knowledge necessary as we determine where these pollutants are and how they can be dealt with.

Microbial mitigation and prevention strategies in building related illness

The search for indoor pollutants takes us to every area in a building, to every process, and to every occupant. "We have found the enemy; now what do we do?!"

Pollutant control begins with their identification, potential sources, and their pathways to unsuspecting occupants. Following these three stages, mitigation and prevention strategies can be defined and implemented. Pollutants are everywhere and the distinction between tolerable and intolerable levels is very important. Absolute control is not a practical goal. Due to this fact, the ALARA principal (As Low As Reasonably Achievable) is a commonly used and accepted guideline.

As preceding articles have discussed, bacteria, fungi, mold, mildew, yeast, and other one-celled organisms are the most potent pollutants in the indoor environment. Although microbes represent biologicals as pollutants, they are in fact representative of all of the classes of pollutants. This allows us to use these potent pollutants as an example for typical pollutant control strategies.

Depending on the pollutant, mitigation and prevention can be very difficult, time consuming, and expensive. In earlier articles we have acknowledged the importance of the full range of pollutants on the integrity of the building materials, the operating systems, the furnishings, productivity, and the health of the occupants. Knowing your building and your occupants is part of the needed defensive strategy but only part of what needs to be done to avoid occupant and "press event" problems.

The following are a few of the 16 Defensive Strategies. These strategies provide some perspective on the countless "solutions" to the SBS/BRI problem.

Architectural design of a building is critical. Everything from the climate to the relationship with other buildings must be considered. This strategy has a direct affect on the sources and pathways that pollutants take. Another area is the materials used in construction are primary sites for microbial growth and contamination. Once these materials are contaminated, remediation can be costly and very time consuming. Also the slightest swing in temperature has dramatic effects on IEQ. Therefore, heating and cooling along with humidity control should be closely monitored and kept in balance.

Other strategies include having baseline audits of your building. This way when emergencies do occur you have something to reference to. This can be a simple audit of the building materials, operating systems, furnishings, and the processes used in the building. Or, it can include actual measurement of suspect particulates, VOC's, and microorganisms. Under certain circumstances it can also be valuable to have an audit of the occupants and staff. The forms and formats for such audits are too complex for this article, but they are available from some government authorities and some service companies.

The importance of having a pollutant control contingency plan for emergency situations and a basic knowledge of your building is essential. One extremely important safeguard, that is often overlooked, is that all buildings should have a clearly written policy designed to respond to building problems. Included in this policy should be a clear scheme of response to environmental issues. Occupant complaints of temperature, air flow, lighting, noise, humidity, and the like should not only have an organized reporting system, but key response people dedicating to handling these issues. Suspected medical problems should also have clear channels for reporting and response.

Understanding the strengths and weaknesses of each strategic component is absolutely essential and often takes outside expertise. Accurate records, good common sense, compliance with regulations and standards, and involving all of the people on a prevention and solutions team will clearly help with and minimize problems associated with indoor environmental quality.

The role of microbes is paramount and their control must be a major target for anyone trying to eliminate the real and potential indoor environmental problems in our buildings. Part VI will cover the unique problems associated with the mitigation and control of microbial pollutants.