Primary Sources of Exposure

1. 1.    Buying Crops from Elsewhere
   

2. 2.    Sniffing the Wind
   

3. 3.    Stirring up Dust
   

4. 4.    Playing in the Dirt
   

5. 5.    Harvesting from Home
   

General rules for assessing the risk of an individual or community to soil based exposures are nearly impossible.  Most people become aware of a potential health risk posed by soil via a rise in public community awareness of a particular source of exposure (industrial activity, corporate farming practice, and so on).  A number of different sources of exposure to the typical individual are worth considering.   For most individuals, exposures through contaminated soil are minimal.  However, when a nearby problem or pervasive contamination exists, soil can become a major source of exposure.  Soil is also important because it is a “catch-all” preview to other sources of exposure. Soil can indicate significant sources of air pollution in the present and of (ground) water pollution in the future.  Soil may be the most quiet of our environmental exposures, but it tells an important story about the rest of the fabulous four (food, air, and water)!

Buying Crops from Elsewhere:

When buying vegetables and food that have been grown in corporate farms or other non-local agricultural operations, it is important to understand both the present farming practices as well as the past history of farming practices on the soils in question.   Many pesticides used 30-40 years ago in agriculture are now prohibited, yet they are persistent in the soil.  Most certified organic produce comes form tested soil which has been tested for these persistent pollutants and is restricted on the addition of other pollutants as part of growing and harvesting crops.  The agricultural extension in most states holds historical information on  soil and gives a good indication of the persistent pollution that when present in soil, can move into the fruits and vegetables that end up on your dinner table.

Sniffing the Wind:

In the vicinity of industrial activity, especially chemical production, many products of manufacturing are expelled into the air.  Those emissions that are heavy or big (particles) enter the air and quickly settle onto surrounding soils.  In this way, the surface of the soil can carry a partial record and history of the dust in the wind.   Breathing in dust, in addition to being a particle hazard to the lungs, can also enable hazardous volatiles to enter the olfactory and respiratory system, eventually breaching the body’s defense mechanisms if inhaled over long periods of time. 

Stirring up Dust:

While outdoor surface soil usually carries a record of what has drifted in from elsewhere, most dust exposures are elevated indoors over those found outdoors.   In addition to containing elements of outdoor air pollution, indoor dust can also carry the toxic residues of household products especially pesticides and rodenticides.   Understanding these exposures requires knowing what industrial activity is nearby (outdoor dust) and the impact of pesticide and related household product use indoors.  Exposures can be substantially reduced by leaving shoes and other dirt covered clothing outside and by sweeping up dust on a regular basis.  Be cautious of vacuum cleaners that, without appropriately small particle or HEPA filters, can simply stir up the dust, elevating your exposure, before the dust settles back down into the carpet.

Playing in the Dirt:

Significant exposures through soil can occur by ingestion (eating the soil).  Children are especially vulnerable because of hand-to-mouth contact.   If you have reason to suspect that the soil in your yard, playground, or school is contaminated, it is worthwhile to have the soil tested for the suspected contaminants and to ensure that both children, gardeners, and others who play in the dirt pay special attention to washing hands after exposure. 

Harvesting from Home:

Backyard gardening is susceptible to unwitting exposure from rural (persistent agricultural pollutants) to urban (industrial and vehicle pollutants) environments.   Healthy backyard gardening should be done with the nature of the soil in mind; testing for most likely pollutants through county laboratories or agricultural extensions is often inexpensive and informs the highest likelihood pollutants to test.   Even if soil is contaminated, backyard gardening can still result in a perfectly healthy harvest via the use of soil amendments (to prevent the contaminants from entering the plant), proper selection of plants (to reduce uptake), and raised beds (which enable plants to take up nutrients predominantly from less contaminated, introduced soil.