Author(s)

STEVEN R. SPENGLER, SAMUEL C. SPENGLER

Abstract

The organochlorine termiticides dieldrin and chlordane were used in the Hawaiian Islands from the mid-1940s until the late 1980s to protect residential and commercial buildings from Formosan termites. The EPA banned their use in 1988, and the 2001 Stockholm Convention listed them as Persistent Organic Pollutants, citing their toxicity, environmental persistence and ecological harm. These chemicals exhibit ‘zombie-like’ persistence. Longitudinal data since the early 1970s show dieldrin concentrations in urban Honolulu drinking water wells surging from under 2 ng/L to 30–60 ng/L, driven by post-1950s residential expansion upgradient of older wells. As Oahu relies on groundwater for over 99% of its drinking water, these trends pose a significant challenge. A simple 1-D transport model predicts dieldrin levels will continue rising for the next 20 years. Despite the potential toxicity of these chemicals, impacted wells have yet to be retrofitted with remedial systems to lower the rising pesticide levels introduced by these wells to the islands water supply system. Dieldrin concentrations in groundwater-fed streams and springs on Oahu have also more than doubled since the mid-1970s, with current averages reaching 25 to 215 ng/L. Conversely, dieldrin levels in urban watershed sediments have declined to concentration levels of around 10% of maximum levels measured prior to the 1988 ban. The ubiquitous occurrence of dieldrin and chlordane in streams and groundwater on Oahu may pose a risk due to biomagnification in the food chain of organisms in coastal embayment’s with limited circulation, such as Pearl Harbor and Kaneohe Bay, which have been receiving an increasing input of these chemicals since the early 1970s.

Keywords

Hawaii, termiticide, dieldrin, chlordane, half-life, groundwater, stream, sediment, wastewater, contamination, bioaccumulation