A hundred years ago, the primary component of house dust was probably horse manure that got tracked indoors. Today tracking is still the primary method by which particles enter the home, but since the old days, we have identified over one hundred particle types and another fifty or more volatile organic compounds (VOCs) that are present in the dust and dirt in the average home. These latter compounds include fragrances and pesticides.

Mold growth is common in many parts of the country. Depending on your locale, the indoor mold spore count will vary from less than 100 per cubic meter of air (desert southwest) to over 6000 (Southeast and Northwest). 

The amount and type of pollen will vary also. Since it doesn’t grow indoors and wildflowers do not contribute much to this problem, it is the weeds, grasses, and tree pollens that are airborne. When they land on the outside walkways or we walk or work in the grass, the particles collect on our shoes and even our clothing, and enter the home in this manner.

Another particle type is diesel exhaust carbon. Allergenic unto themselves, these particles also carry antigens from pollen such as grass and ragweed. The average number of these particles can be several thousand, depending on how close one lives to an intersection, or what is parked in the garage.

The list goes on from here: fragranced cornstarch particles from body talc, dust mites , cockroaches and their body parts and feces, plant parts (especially grasses), cat and dog antigen, road dust, and so many others.

The number of dust particles in the air of virtually every home is in the tens of millions per cubic meter. Sometimes our bodies can’t cope with this number or the type of particle. (It can take only a half-dozen ragweed or Bermuda grass pollen grains to cause a clinical reaction.)

There are several solutions to the dust problem and our indoor exposure to particles. First, take off your shoes at the door...