Some Facts

The concept of bioaccessibility can be defined as the quantity or fraction, which is released from the ingested contaminated food or food containing contaminated solid particles from soil or dust in the gastrointestinal tract and becomes available for absorption. Bioaccessibility measurements are essential in the protection of humans and mammals from contaminated soils where the assimilated dose is in part defined by the process of ingestion.

The term bioavailability includes the utilization of a potentially harmful substance and can be therefore defined as the fraction of ingested contaminant or compound that reaches the systemic circulation. It can be defined also as the fraction of an ingested dose that crosses the gastrointestinal epithelium and becomes available for distribution to internal target tissues and organs.

Risk assessments are carried out to examine the effects of an agent on humans (Health Risk Assessment) and ecosystems (Ecological Risk Assessment). Environmental Risk Assessment (ERA) is the examination of risks resulting from technology that threaten ecosystems, animals and people. It includes human health risk assessments, ecological or ecotoxicological risk assessments, and specific industrial applications of risk assessment that examine end-points in people, biota or ecosystems.

A human health risk assessment is the process to estimate the nature and probability of adverse health effects in humans who may be exposed to chemicals in contaminated environmental media, now or in the future.

The most commonly listed potentially toxic elements (PTE) are arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu) nickel (Ni), lead (Pb) and zinc (Zn). Some of these PTEs are essential for living organisms, like Cr, Cu, Ni and Zn, which are required at low concentrations and become toxic at higher levels of exposure. Elements including As, Cd and Pb are not required by organisms at any level and are toxic. The degree to which a contaminant may dissociate from soil solids and become available to a target organism (bioaccessible) is therefore a determining risk factor. MPB 1500 enables incubation of soil samples in temperature controlled water-bath with end-over-end rotation of samples, mimicking conditions of gastrointestinal tract.

The European network joined under the Bioaccessibility Research Group of Europe (BARGE) has established the Unified Bioaccessibility Method (UBM), an in-vitro method with defined Standard Operation Procedure (SOP) for the preparation of extracts from contaminated soil or other geological material that are representative of the concentration of potentially harmful elements in a simulated human gastrointestinal tract. The BARGE has evaluated the method in an international inter-laboratory comparison study. Soils or other geological materials, in sieved or crushed form, are extracted in an environment that simulates the basic physicochemical conditions of the human gastrointestinal tract. MPB 1500 provides temperature controlled water-bath with rotator for series of samples.

Reliable analysis of the potential hazard to children from ingestion of lead in the environment depends on accurate information on a number of key parameters, including (1) lead concentration in environmental media (soil, dust, water, food, air, paint, etc.), (2) childhood intake rates of each medium, and (3) the rate and extent of lead absorption from each medium (“bioavailability”). Knowledge of lead bioavailability is important because the amount of lead that actually enters the blood and body tissues from an ingested medium depends on the physical-chemical properties of the lead and of the medium. For example, lead in soil may exist, at least in part, as poorly water-soluble minerals, and may also exist inside particles of inert matrix such as rock or slag of variable size, shape, and association. These chemical and physical properties may tend to influence (usually decrease) the absorption (bioavailability) of lead when ingested. Thus, equal ingested doses of different forms of lead in different media may not be of equal health concern.

The TCLP, or Toxicity Characteristic Leaching Procedure is designed to determine the mobility of both organic and inorganic analytes in liquid, solid, and multiphasic wastes.