In 1992, a field study and associated risk assessment was sponsored by the Empire State Electric Energy Research Corporation (ESEERCO) and performed by O'Brien & Gere Engineers, Inc. (OBG) to evaluate the potential ecological and human health impacts related to the application of five supplemental/remedial Osmose wood preservatives to in-service utility poles. The remedial preservatives and principal active ingredients evaluated were:
The ESEERCO field study established that essentially no preservative active ingredients were released to surrounding ground water, surface water or soil in the 17-month post-treatment sampling period. Researchers concluded that the supplemental utility pole treatments did not cause measurable post-application impacts to Adirondack Park wetlands. Researchers also performed a risk analysis using computer generated estimates of preservative concentrations released from the remedially treated poles. Predicted estimates of active ingredient concentrations were found to be significantly higher than actual measured levels in soil, surface or ground water, yet were still lower than USEPA drinking water criteria. Thus, the modeled analyses further supported the conclusion that the supplemental wood pole treatments did not present a significant health risk to biota or humans.
Since the 1992 ESEERCO study, Osmose's remedial preservative technologies have been reformulated to be even more environmentally responsible. As such, Osmose engaged OBG to perform a risk assessment to establish the potential ecological and human health effects, if any, related to the application of the following current remedial wood pole preservatives and their respective active ingredients:
For this risk analysis, OBG Researchers utilized a ground water transport computer model similar to that utilized in the ESEERCO study to generate "worst case" estimates of preservative release in stormwater and groundwater at a 15-meter distance downgradient from the pole. The human exposure scenario assumes that a potable water well is developed at this point and that humans are exposed to product active ingredients via ingestion, dermal contact, and inhalation. The ecological exposure scenario assumes that aquatic receptors are exposed to product active ingredients that are discharged to a stream located at this point. Preservative release was also modeled at a 3-meter distance downgradient from the pole to assess the appropriateness of Osmose's recommended set-back distance of 3 meters from bodies of water to mitigate risk to aquatic receptors.
Risk to human receptors from exposure to boron and copper was evaluated using USEPA Regional Screening Levels (RSLs) for tap water. The mitc tap water standard was derived herein using existing toxicological literature and RSL methodology. Risk to aquatic receptors was determined by comparing the modeled surface water concentrations to benchmarks derived from the USEPA's on-line ECOTOX database, and the USEPA Biological Assistance Technical Group (BTAG) Freshwater Screening Benchmarks.
Predicted potable well concentrations of copper and boron from Osmose's remedial preservative formulations MP500-EXT, Pole Wrap CB, and Hollow Heart CB were found to be below the respective RSLs established by the USEPA for tap water. Predicted potable well concentrations of mitc from Osmose's mitc-based fumigant formulations were also found to be below the derived RSL for tap water.
The predicted surface water concentrations for all active ingredients from Osmose's remedial preservative formulations were below the established USEPA BTAG (chronic exposure) and ECOTOX (acute exposure) benchmarks for aquatic receptors. When the 15-meter distance is shortened to 3 meters in the risk analysis, predicted surface water concentrations remain below BTAG and ECOTOX benchmarks. These results support the set-back distance of 3 meters from surface water bodies for these remedial preservative formulations to be protective of aquatic receptors.
As with the 1992 ESEERCO study, predictive estimates of preservative release for this computer modeled risk assessment are conservative. This is particularly true when considering the cautious nature of the USEPA RSL residential tap water exposure scenario of bathing 42.6 minutes/day; drinking 2.5 liters/day; for 350 days/year for 26 years. Even with this conservative approach, predicted surface water and potable well water concentrations remained below the environmental and human health thresholds established by EPA. Based on the results of this risk assessment, it is concluded that supplemental utility pole treatments of MP500-EXT, Pole Wrap CB, Hollow Heart CB, DuraFume, WoodFume, and MITC-FUME provide minimal risk to the environment and human health when properly applied.
Doug Herdman is the Director of Science and Manufacturing at Osmose. He holds a BS in Wood Science and a MS in Environmental and Resource Engineering, both from SUNY-ESF at Syracuse. He has more than 20 years of experience formulating and testing remedial wood preservatives technologies. In his current role, he oversees the design, development, and commercial production of Osmose's industry-leading wood preservative technologies.