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Using propensity scores to estimate the effects of insecticides on stream invertebrates from observational data

Environmental Toxicology and Chemistry

By:
, ,
DOI: 10.1897/08-551.1

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Abstract

Analyses of observational data can provide insights into relationships between environmental conditions and biological responses across a broader range of natural conditions than experimental studies, potentially complementing insights gained from experiments. However, observational data must be analyzed carefully to minimize the likelihood that confounding variables bias observed relationships. Propensity scores provide a robust approach for controlling for the effects of measured confounding variables when analyzing observational data. Here, we use propensity scores to estimate changes in mean invertebrate taxon richness in streams that have experienced insecticide concentrations that exceed aquatic life use benchmark concentrations. A simple comparison of richness in sites exposed to elevated insecticides with those that were not exposed suggests that exposed sites had on average 6.8 fewer taxa compared to unexposed sites. The presence of potential confounding variables makes it difficult to assert a causal relationship from this simple comparison. After controlling for confounding factors using propensity scores, the difference in richness between exposed and unexposed sites was reduced to 4.1 taxa, a difference that was still statistically significant. Because the propensity score analysis controlled for the effects of a wide variety of possible confounding variables, we infer that the change in richness observed in the propensity score analysis was likely caused by insecticide exposure. ?? 2009 SETAC.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Using propensity scores to estimate the effects of insecticides on stream invertebrates from observational data
Series title:
Environmental Toxicology and Chemistry
DOI:
10.1897/08-551.1
Volume
28
Issue:
7
Year Published:
2009
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1518
Last page:
1527
Number of Pages:
10