In this document, we selected copper pyrithione (CuPT) as using booster biocide in antifouling paint. Ecological risk assessment performed using the estimated environmental concentration (EEC) of CuPT in Tokyo Bay. The EEC of CuPT estimated by using the result that reproduced the emission and fate by numerical model.
The principal use for CuPT is in antifouling paints, on fish nets, as the antifoulant on marine structures and as an antifoulant against algae. The main emission sources of CuPT include; 1) commercial shipping and ports; 2) fish farms and trap nets; and 3) other emission sources such as fishery harbors and marinas, docks and ship yards, and intake pipes used for marine power plants, urban wastewater and waste disposal.
The EEC of CuPT in Tokyo Bay was estimated using a chemical fate model after restaging the flow field and the distribution of the suspended matter. We focus on commercial ships and commercial shipping ports in which the influence from antifouling paints used on the hulls of the ships entering ports and mooring is believed to be serious. The CuPT load from vessel hulls is estimated from the maximum, minimum and average load using the concentration of CuPT (1.45-3.66 wt %) in antifouling paints. The calculations are based on the idea that in 2008 TBT antifouling paints will be substituted with TF antifouling paints when the IMO brings the AFS treaty into effect.
In this document, the limit of toxicity reported in the literature is set to 0.25 μg/L for Skeletonema costatum (at the 96-hour NOEC – no observed effect concentration) and the UF (uncertainty factor) is set to 100, based on a previous report on the toxicity of CuPT. Ecological risk assessments use the MOE method of comparison with the limit of toxicity and the UF.
When the concentration of CuPT is 3.66 wt %, it poses a significant ecological risk as the ports of Tokyo Bay. When the concentration is set to 1.45 wt % and 2.00 wt %, CuPT poses a significant risk as the MOE values in the surface layer are always below the UF in each of the commercial ports. Ecological risk is unlikely in the other areas in other seasons. Ecological risk from CuPT is unlikely along the navigation routes, as the MOE values are always greater than the UF for 3.66, 1.45 and 2.00 wt % content of CuPT all year round.
In this study, the ecological risks posed by TBT and CuPT were compared. In the case of TBT, there is significant ecological risk in most of the study area because the MOE values are below the UF all year round. In the case of CuPT, there is significant risk in commercial ports and some of the navigation routes, but this risk does not extend to the whole area. Although there is significant ecological risk in commercial ports, substituting TBT with CuPT will lead to a decreased ecological risk in most of the study area.
Copper pyrithione (CuPT) Risk Assessment Document was produced under the Comprehensive Chemical Substance Assessment and Management Program funded by the New Energy and Industrial Technology Development Organization (NEDO).
The full text of CuPT Risk Assessment Document (in Japanese) was published by Maruzen Co., Ltd. in March 2007.