Derivation of Predicted No Effect Concentrations (PNECs) for Heavy Metals in Freshwater Organisms in Korea Using Species Sensitivity Distributions (SSDs)

Jinhee Park,Sang Don Kim

doi:10.3390/min10080697

Jinhee Park, Sang Don Kim

Open Access

https://doi.org/10.3390/min10080697

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Journal: Minerals	Publication Date: Aug 6, 2020
Citations: 11	License type: CC BY 4.0

Affiliation: Gwangju Institute of Science and Technology

Abstract

Natural and artificial heavy metal exposure to the environment requires finding thresholds to protect aquatic ecosystems from the toxicity of heavy metals. The threshold is commonly called a predicted no effect concentration (PNEC) and is thought to protect most organisms in an ecosystem from a chemical. PNEC is derived by applying a large assessment factor (AF) to the toxicity value of the most sensitive organism to a chemical or by developing a species sensitivity distribution (SSD), which is a cumulative distribution function with many toxicity data for a chemical of diverse organisms. This study developed SSDs and derived PNECs using toxicity data of organisms living in Korea for four heavy metals: copper (Cd), cadmium (Cu), lead (Pb), and zinc (Zn). Five distribution models were considered with log-transformed toxicity data, and their fitness and uncertainty were investigated. As a result, the normal distribution and Gumbel distribution fit the data well. In contrast, the Weibull distribution poorly accounted for the data at the lower tails for all of the heavy metals. The hazardous concentration for 5% of species (HC5) derived from the most suitable model for each heavy metal was calculated to be the preferred PNEC by AF 2 or AF 3. PNECs, obtained through a suitable SSD model with resident species and reasonable AF, will help protect freshwater organisms in Korea from heavy metals.

Highlights

The use of heavy metals and their natural or artificial exposure to the environment have continued for decades
The resident species were identified by the National List of Species of Korea [16] supported by the National Institute of Biological Resources and the toxicity values showing equivalent taxonomic hierarchy with resident species were used in sensitivity distribution (SSD) development
Plant species’ toxicity data were not available for some heavy metals, the minimum amount of data required for the SSDs was satisfied, including the important species

Summary

Introduction

The use of heavy metals and their natural or artificial exposure to the environment have continued for decades. Cadmium (Cd) and lead (Pb), the primary toxic metals, cause neurophysiological, biochemical, and behavioral changes in aquatic organisms, leading to fatal damage such as tissue and organ damage, spinal deformity, and dyspnea [1]. Some heavy metals, such as copper (Cu) and zinc (Zn), are essential for living organisms in trace amounts, but cause toxicity if essential metals exceed metabolic requirements [1]. It is necessary to find a threshold called the predicted no effect concentration (PNEC) that can protect organisms from heavy metal exposure in aquatic environments. The AF method involves considerable uncertainty because limited toxicity data cannot reflect the effect of a Minerals 2020, 10, 697; doi:10.3390/min10080697 www.mdpi.com/journal/minerals

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