A METHOD FOR EVALUATING CONSUMER PRODUCT INGREDIENT CONTRIBUTIONS TO SURFACE AND DRINKING WATER: BORON AS A TEST CASE

Abstract

Boron is a ubiquitous element that enters surface waters via two main routes, weathering of boron-containing rock (e.g., borosilicates) and release of boron in cleaning products through disposal to wastewater treatment systems. Recently, concentrations of boron deemed safe for humans and aquatic organisms, via drinking and surface water exposures, have been published. In comparison, however, little has been published regarding the concentrations and distribution of boron in surface waters. This manuscript describes the geographic distribution of boron in the U.S. and California and details a unique method for estimating the amount of boron in receiving waters from consumer product sources using ROUT, a novel deterministic U.S.-scale surface water modeling system, and the USEPA STORET database. ROUT is a national model that predicts chemical concentrations in U.S. rivers and streams and surface drinking water intakes that receive discharges from publically owned wastewater treatment plants (WWTPs). Over 500,000 river miles are systematically routed through the 18 major hydrologic regions of the continental U.S., excluding Alaska and Hawaii. A geographic information system interface coupled to ROUT provides a readily interpretable map of the predicted influences of environmental loadings on environmental concentrations. In addition, this capability allows for comparisons of ROUT output versus other water quality databases (i.e., STORET database) that are georeferenced. Further, for consumer product ingredients that are measured in surface waters, it may be possible to estimate the relative contribution of that ingredient in surface waters from consumer use. Concentrations of boron in receiving waters, predicted concentrations from consumer products, and the percentage of boron from consumer products were determined for California and the continental U.S. Over 55,000 records of dissolved boron were found in STORET between 1984 and 1993. At least one record was found in 667 counties in 44 states, most west of the Mississippi River. Based on all measurements, the median and 90th percentile boron concentrations for the U.S. were 0.076 and 0.387 mg B/L, respectively. The percent contribution of boron in surface waters from consumer product use and disposal to WWTPs was found to be dependent on the extent of sewage treatment plant effluent/receiving water dilution and natural background boron levels. Where background boron levels and dilution factors were lowest, the percent consumer-derived contributions were the greatest.