Human Biomonitoring is a scientific technique for assessing human exposures to environmental agents and their effects, based on sampling and analysis of an individual's tissues and fluids. While blood, urine, breast milk and expelled air are most commonly measured, hair, nails, fat, bone and other tissues may also be sampled. This technique takes advantage of the knowledge that environmental agents that have entered the human body leave markers reflecting this exposure. The marker may be the agent itself or a breakdown product, but it may also be some change in the body resulting from the interaction of the agent or its breakdown product(s) with the individual, such as alterations in the levels of certain enzymes or other proteins which may lead to modifications of normal body processes
In health-related fields, a reference range (RR) usually describes the variation of a measurement or value in healthy individuals. The standard definition of a RR in laboratory medicine is usually defined as the prediction interval between which 95% of values of a reference group fall into.
The DL, also known as LOD (Limit of Detection), is the lowest amount of an analyte in a sample that can be detected, but not necessarily quantitated as an exact value. The DL may be expressed as
DL = 3.3*SD/S
where SD = standard deviation of the response and S = the slope of the calibration curve.
This is the lowest concentration or value of an analyte that can be identified and quantitatively measured.