Reference values are provided by governmental agencies for some, but not all toxins. A reference value indicates the upper value as statistically established from the generally healthy population to a given environmental toxin. In simple terms, the upper reference range can vary depending on the overall environmental situation. People living in a clean environment, will have healthy people that are less exposed to environmental toxins and hence the statistical evaluation will provide an upper reference range for a given toxin that may be lower than that of a population living in a polluted area.
Reference ranges (RR) are established on so-called healthy people, and these RR are used to identify subjects with an increased level of exposure. However, levels exceeding these RR do not represent health related criteria i.e. a urine Arsenic level mildly exceeding the RR indicates a slightly greater exposure as has been determined for the average population. A higher than expected exposure may not indicate a significant risk. Symptoms of intoxication may not (yet) be present or be diffuse.
To establish the risk factor, further diagnostics tests are warranted.