In documenting actual contamination, evidence is needed that not only have hazardous substances entered the water or sediments (observed release criteria), but that these substances have moved through the biological food chain to the organisms that humans consume.
There are three criteria that can establish actual contamination of the human food chain. Please read carefully HRS rule page 51620.
The first criterion is the most commonly used and is the simplest: show that there has been an observed release of a hazardous substance with a BPFV of 500 or greater.
- The inference behind this criterion is that
substances with rather high bioaccumulation potential are the ones that are
most likely to have penetrated through the biological food chain and be
found in the tissue of organisms that humans eat.
Substances with high bioaccumulation factor values
include many polyaromatic hydrocarbons (PAHs), most pesticides, and metals
such as cadmium, copper, mercury, radium, selenium, and zinc.
- Bioaccumulative substances tend to sorb and are more apt to be found in sediment samples than aqueous samples.
Actual contamination is also assessed when a fishery has been closed because of the presence of a specified hazardous substance and that this same substance is found in a observed release from the site.
- The inference behind this criterion is that the closure of the fishery was in response to a health threat due to the presence of the substance and that the presence of that same substance in the observed release documents that the site has contributed to the health threat.
The third criterion is the most definitive of actual contamination but the least used: document an observed release by a sample from an essentially sessile, benthic, human food chain organism.
- Especially in fresh water, the essentially sessile,
benthic organisms may not be locally consumed.
- It is difficult to detect many substances in a biological matrix unless they contain chlorine or metals.
The sampling point(s) that document actual contamination of the human food chain are used to establish a zone of actual contamination that extends from the most downstream (or farthest) sample back to the PPE.
There are two ways to determine Level I; both involve tissue samples because the benchmarks are stated in terms of milligrams per kilogram of edible tissue.
- When preparing tissue samples for shipment, select only the edible portions. If fishermen cook the fish skin down, send the fillet and attached skin as most representative of risk. If further portions of the organism are consumed, document that fact and send those edible portions. Fatty portions and livers are apt to show high bioaccumulations.
Level I concentration can be established when an observed release is documented by a sample from an essentially sessile, benthic, human food chain organism.
- The "essentially sessile, benthic" establishes that
the organism stays put so that background and release levels can be
- The "human food chain organism" establishes that
the observed release substances have impacted organisms that human beings
- If substances that meet the observed release criteria also meet or exceed a human food chain benchmark individually or in the aggregate (the I or the J index), Level I concentrations are established.
Level I concentrations can also be established by a fish tissue sample, and other non-sessile, benthic organisms, providing all three criteria of HRS rule, page 51620 are met.
- Non-sessile, benthic organisms like fish move
around and cannot, in themselves, be used to establish an observed release or
a zone of actual contamination.
Within the zone of actual contamination
established by other samples (aqueous, sediment, tissue) a "territorial"
aquatic organism is caught, and a substance found in the organism's tissue
was also found in the documentation of the zone of actual contamination,
the HRS assumes that the load of contamination found within the
organism reflects, at least in part, the impact of contamination
attributable to the site. The contamination level in the organism is
compared against benchmarks and may establish Level I concentrations
(HRS Guidance Manual, Highlight 8-48 : Samples and Criteria for Level I and Level II Concentrations in the Human Chain Threat, page 299).
- The HRS Guidance Manual, Highlight 8-47 : Use of Tissue Samples from Aquatic Organisms, page 297 gives
examples of aquatic organisms that are apt to spend extended periods of time
within the boundaries of actual food chain contamination.
- The location where the organism was caught can document a zone of Level I concentrations if all the criteria are met.
- The HRS Guidance Manual, Highlight 8-47 : Use of Tissue Samples from Aquatic Organisms, page 297 gives examples of aquatic organisms that are apt to spend extended periods of time within the boundaries of actual food chain contamination.
Zones of Level I, Level II, and potential contamination for the human food chain threat are established, based on the sampling points discussed above, in the same manner that zones are established for the drinking water threat.
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