Pharmaceuticals entering water systems are a growing environmental issue. The Predicted No-Effect Concentration (PNEC) is an important tool used to assess and control these risks.
This blog explains what PNEC is, why it matters, and how it is calculated for pharmaceutical compounds.
Table of Contents
What is PNEC?
PNEC stands for Predicted No-Effect Concentration, pronounced “pea-neck.” It is the level of a chemical (often pharmaceuticals) below which no harmful effects are expected in the environment. PNEC is widely used in ecotoxicology and environmental risk assessments to protect ecosystems and set limits for pollutants.
PNEC values are deliberately conservative. They are calculated to safeguard even the most sensitive species in an ecosystem. These values are based on laboratory tests and are used to determine safety thresholds for pollutants entering water systems.
How is PNEC Determined?
The process of determining PNEC involves studying the toxicity of a substance on aquatic organisms and accounting for uncertainties. Two main methods are commonly used:
In this method, scientists use the toxicity value from the most sensitive species tested. They divide this value by an “assessment factor” to adjust for uncertainties, such as limited data, variability between species, or differences between lab and real-world conditions.
This approach is simple and widely used. However, it can lack accuracy when data from multiple species are available.
The SSD method uses toxicity data from many species to create a sensitivity curve. This curve shows how different organisms respond to the substance. The PNEC is set at the 5th percentile of the curve, thereby protecting 95% of the species.
This method is more precise because it uses a broader dataset. However, it requires more information, which may not be available for new pharmaceuticals with limited testing data.
Both methods are used to ensure PNEC values are protective of ecosystems. The choice of method depends on the quality and amount of available data.
Pharmaceuticals in Aquatic Systems
Pharmaceuticals are designed to interact with biological systems. This means they can harm aquatic organisms even at very low levels. Pharmaceuticals make their way into aquatic systems through several routes, including human waste, industrial releases, and runoff from farms. Wastewater treatment often cannot fully remove these substances. As a result, pharmaceutical residues may build up in rivers, lakes, and oceans.
Even in small amounts, pharmaceuticals can:
(1) Disrupt the hormonal systems of aquatic creatures, like fish.
(2) Interfere with the reproduction and growth of algae and small invertebrates.
(3) Alter behaviours needed for survival, such as feeding or mating.
PNEC in Pharmaceutical Risk Assessment
PNEC is essential for assessing risks and shaping environmental policies. Regulators compare the PNEC to the Predicted Environmental Concentration (PEC). PEC is the estimated amount of a substance in the environment. The PEC/PNEC ratio indicates the risk level.
If PEC/PNEC is < 1, the risk is considered low. If PEC/PNEC is > 1, further action may be needed, such as a refined risk assessment or new measures to reduce the substance’s presence.
PNEC values are important for the following:
• Drug Approvals: Pharmaceutical companies must include PNEC data in Environmental Risk Assessments (ERA) when seeking approval for new drugs.
• Wastewater Treatment: PNEC data identify substances that require advanced treatment methods, like activated carbon filtration.
• Environmental Standards: Policymakers use PNEC values to set safe water quality standards.
Conclusion: PNEC Testing for Pharmaceuticals
Determining PNEC is a critical step in understanding and reducing the environmental impact of pharmaceuticals. It helps establish safe levels for these substances. As a result, PNEC analysis protects aquatic ecosystems and promotes sustainable medicine use.
At Southern Scientific Services, we provide expert support to pharmaceutical companies conducting environmental risk assessments. Our services include PNEC testing, regulatory compliance, and risk management.
