While direct measurements of biomarkers can give you accurate exposure prevalence, it can be time consuming and expensive. Developing a model can be an alternative to estimate exposure. A model is a basically a mathematical equation that inputs known variables to asses exposure levels. The four main components of a model are environment, agent, host, and time. Below are the four components with examples of types of variables that may be used in the model equation:

1. Environment (partition gradient, physical area)
2. Agent (chemical properties, concentration)
3. Host (health, age, exposure pathway)
4. Time (length of exposure)

A model can more effective than measuring biomarkers, not only with less time and expense, but with greater flexibility by allowing the variables to change.

For more information on biomarkers and modeling, please see these websites:

Pesticides for which biological monitoring methods are available as metabolites in urine http://www.hsl.gov.uk/services/pest_list2.htm#top

Lawn and Garden Pesticides: A Review of Human Exposure & Health Effects Research http://www.toronto.ca/health/hphe/pdf/pesticides_lawnandgarden.pdf

Indicator, Exposure: Biologic markers of pesticides or pesticide metabolites in human tissue http://www.cdc.gov/nceh/indicators/pest_bioMark.htm

Monitoring and Evaluating Pesticide Exposure
http://www.cdpr.ca.gov/docs/pressrls/dprguide/chap6.pdf

Biomarkers in toxicology versus ecological risk assessment.Toxicology. 2002 Dec 27;181-182:517-21.

Assessment of variability in biomonitoring data using a large database of biological measures of exposure. AIHA J (Fairfax, Va). 2002 Jul-Aug;63(4):390-401.

Pesticides in Drinking Water Wells http://ace.orst.edu/info/npic/factsheets/drinkingwater.pdf