Multi-phase Approach Monitoring Strategy
The Multi-phase Approach Monitoring Strategy (Multi-phase Approach) consists of three phases – Phase 1: Screening Study, Phase 2: Verifying Magnitude of Contamination and Phase 3: Assessing Geographic Extent. When funding is limited, an Enhanced Phase 1 may be employed. The Enhanced Phase 1 involves more sampling than a typical Phase 1, but Phases 2 and 3 are not carried out.
Phase 1 – Identify frequently fished sites, where commonly consumed fish and shellfish target species are found, to assess whether they are contaminated and may pose potential human health risk from consumption. This screening study entails sampling fish from multiple sites for chemical contamination where sport, subsistence, and/or commercial fishing is conducted.
Phase 2 – Assess and verify the magnitude of tissue contaminant concentration by resampling at sites that had fish tissue contamination in Phase 1.
Phase 3 – Assess geographic extent of contamination if necessary. In small to medium lakes, the fish contaminant concentrations may not vary spatially and may have been fully assessed in Phase 1 or 2. For larger lakes or lake systems, collect fish at additional sites. Another objective is to establish levels of relative contamination in 2-3 selected size/age classes of commonly consumed target species by analyzing tissue of fish with a range of lengths.
The allocation of limited funds to an Enhanced Phase 1 Screening Study or to the more intensive studies that include Phases 2 and 3 should always be guided by the goal of conducting adequate sampling of fish and shellfish resources to ensure the protection of public health. Sampling and analysis capabilities will be determined by available funding resources. Ideally, funding will be allocated for a Phase 1 Screening Study at as many sites as is deemed necessary while reserving adequate resources to conduct subsequent Phase 2 and 3 studies at sites where excessive fish tissue contamination is detected.
When should this approach be used?
The Multi-phase Approach is best when there are no fish contamination data from previous studies and funding is not the primary constraint.
Sampling Design Elements
| Phase 1: Screening Study | Phase 2: Verifying Magnitude of Contamination | Phase 3: Assessing Geographic Extent |
|---|---|---|
| Sample target species where fishing occurs at sites that have an increased likelihood of contamination (based on observation or history) and at sites presumed to be uncontaminated. | Sample target species at each site identified in the screening study where fish/shellfish tissue concentrations exceed human health fish tissue levels to assess the magnitude of contamination. | Sample at additional sites in the waterbody to assess the geographic extent of the contamination in the waterbody. |
| Phase 1: Screening Study | Phase 2: Verifying Magnitude of Contamination | Phase 3: Assessing Geographic Extent |
|---|---|---|
|
Select target species from commonly consumed species using the following additional criteria - known to bioaccumulate high concentrations of contaminants and distributed over a wide geographic area. Recommended: Inland freshwaters and Great Lakes – at least two fish species (including one bottom-feeder) and one mollusk if appropriate for the waterbody Marine/estuarine – at least two fish species (including one bottom feeder and one pelagic species), one mollusk, and one crustacean if appropriate for the waterbody |
Resample target species at site where they were found to be contaminated in Phase 1. | Target species found to be contaminated should be sampled at additional sites in the waterbody. Sample 2-3 size classes of the target species found to be contaminated in Phase 2. |
| Phase 1: Screening Study | Phase 2: Verifying Magnitude of Contamination | Phase 3: Assessing Geographic Extent |
|---|---|---|
| In many U.S. waters, fish are contaminated with multiple pollutants. Contaminants to Monitor in Fish and Shellfish Advisory Programs has the EPA's recommendations on contaminants that fish advisory programs should consider monitoring in fish and shellfish. | Analyze only for those target contaminants from Phase 1 that exceeded human health fish tissue levels. | |
| Phase 1: Screening Study | Phase 2: Verifying Magnitude of Contamination | Phase 3: Assessing Geographic Extent |
|---|---|---|
| Collect sufficient fish for either individual or composite samples (5 individual fish processed together as a single sample). for each target species. Fish may be processed as fillet or whole as determined by the consumption habits of the target population. Collect, process, and analyze composite samples of edible portions of target shellfish species. | Same (individual or composite) as Phase 1 screening study. | Same as phase 1 screening study but collect composite samples for two or three size classes of each target species as appropriate. |
Note: Program staff may opt for individual whole fish samples, or individual fish plug samples. Although the skin-on fillet-based sample is the general recommendation for fish consumption advisory sampling, additional information can be obtained by analyzing other sample types. Sample type should reflect dietary and fish preparation methods of the target audience of concern.
Enhanced Phase 1 Approach
An Enhanced Phase 1 involves more sampling than a typical Phase 1 and Phases 2 and 3 are not carried out. An Enhanced Phase 1 may be unavoidable if monitoring resources are limited or if an advisory must be issued based on detection of elevated concentrations in one composite sample. If monitoring resources are severely limited, precluding performance of any Phase 2 or 3 activities, EPA recommends three sampling options for collecting additional samples during the Enhanced Phase 1. These options are:
- Collect replicate composite samples for each target species.
- This option provides additional information on size-specific levels of contamination that may allow fish monitoring programs to issue a fish consumption advisory for only the most contaminated size class while allowing the other size class of the target species to remain open to fishing. Assessors could analyze the composite sample from the largest size class first. If any human health fish tissue levels are exceeded, analysis of the smaller size class composite samples could then be conducted. This option, however, does not provide any additional information for estimating the variability of the contamination level in any specific size class. To obtain information for estimating the contamination level range in the target species, the protocol could be to separately analyze each individual fish specimen in any composite of a species that had been found to exceed the human health screening levels. However, this option of analyzing individual fish within a composite sample would increase analytical costs.
- Collecting replicate composite samples for each target species
- This option provides additional statistical power that would allow the advisory team to estimate the variability of contamination levels within the one size class sampled. This option does not provide information on size-specific contamination levels.
- Collect replicate composite samples for each of two size/age classes of each target species found to be contaminated above human health fish tissue levels.
- This option provides both additional information on size-specific contamination levels and additional statistical power to estimate the variability of the contaminant concentrations in both size classes of the target species. If resources are limited, you could analyze the replicate sample for the largest size class first; if the human health screening levels are exceeded, analysis of the smaller size class composite sample could then be conducted.
If the Enhanced Phase 1 results are the sole basis for developing a fish consumption advisory, this should be characterized as a more conservative fish consumption advisory.
