Although total numbers of people exposed were generally calculated to be relatively small, the assumption that risks could be severe to those who are exposed drove higher human health rankings of this issue. Projects typically arrive at a risk estimate for human health using the data that is available with an explanation of the limitations associated with the estimate. According to the technical report, the resulting population risk, 3.5 X 103, overstates the actual risks for several reasons. The model also conservatively assumes that all target wells are equally affected regardless of distance, and that all target homes are drinking ground water. The risk management focus on human health has left sizable gaps in the understanding of risks to ecosystems.
Projects report a lack of discussions in site investigation reports about risks to the environment.
Ecological impacts from hazardous or toxic wastes include impacts for those species in direct contact with contaminated soil, sediments, and surface waters, or indirectly from the consumption of contaminated vegetation or animal tissue. With remediation of these sites unlikely, natural recovery time is long, due to the persistence of many contaminants. In lieu of sitespecific data, several projects reported more general evidence supporting a low risk to ecosystems. Even though most projects concluded that risks to ecosystems are in the low to medium range, reports reflect an uneasiness about the lack of data on ecosystem impacts, particularly regarding the long term effects that low concentrations of contaminants may have on terrestrial systems. Isolating Residual Risk Project reports convey a frustration in attempting to estimate risks to human health and the environment from waste sites managed under Superfund or a state remediation program.