Factors confounding

SatoA. 1993. Confounding factors in biological monitoring of exposure to organic solvents. IntArch Occup Environ Health 65 S61-S67. 

For each of the suggested water and sediment indicators, there are possible confounding environmental factors that are not related to changes in Hg loading, but that could result in responses in some of the indicators. Several of these confounding factors have been previously mentioned, but a general discussion of them is provided here. 

To identify ancillary data needs and potential confounding factors that should be considered or documented to ensure the defensible interpretation of data on monitored biological indicators... 

Temporal response to changes in abundance of MeHg A slow rate of response to altered MeHg loading could increase the potential for interference by confounding factors, whereas a rapid response, coupled with high intraannual variability would hinder identification of multiyear trends Hours to days Hours to days... 

Steps to Constrain Confounding Factors AND Enhance Interpretation... 

Monitoring programs should be designed to limit the effects of confounding factors that impair our ability to discern both trends in MeHg concentrations in aquatic... 

Ability to isolate impacts of confounding factors other than changes in mercuiy emissions and deposition... 

Criteria 1) Relevance to human health endpoints. 2) Sensitivity to change in loadings. 3) Overall historical data quality. 4) Data collection infrastructure. 5) Feasibility of data collection and analysis. 6) Ability to adjust for confounding factors. 7) Understanding of linkages with rest of ecosystem. 8) Broad geographic distribution. 9) Well-known life history (for fauna). 10) Nonintrusive sampling. 

The moiutoring framework should be designed to miiumize the iirfluence of such factors or to control for them in the analysis process. While no moiutoring strategy can account for all possible complexities, the authors believe this monitoring framework has identified the best currently available solutions to address problems created by these confounding factors. 

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