Measurements have been carried out in wastewater in several European countries including Sweden, but the substance has not been detected. Degradation data for prometazine is missing.
Studies on the toxicity have only been carried out on one specie (water flea shows effects on reproduction at 180 μg/L), that makes a calculation of the environmental risk becomes uncertain.
Several independent sources report an estimated fat solubility (log Pow) above 4, indicating that the substance has a high potential for bioaccumulation.
Diazepam and oxazepam are included in the Stockholm County Council's table of pharmaceuticals with risk for negative environmental impact according to the environmental program 2017-2021 based on measured concentrations of oxazepam in Swedish surface water and in Swedish wild fish, and that these concentrations are very close to those affecting fish behavior. Diazepam is to some extent metabolised from oxazepam and may therefore contribute to this risk.
Prometazin is not as well investigated for effects, but the substance has a fat solubility that indicates high potential for bioaccumulation. However, despite investigations in many countries, including Sweden, prometazin has not been detected in wastewater. Prometazin is therefore considered to be better from an environmental point of view than oxazepam.
The risk assessment can not be excluded, according to Fass.se, is due to persistence and toxicity studies being incomplete, why a risk calculation has not been possible. It is voluntary for manufacturers to provide information on the environmental impact.
Author: Health and Medical Care Administration, Region Stockholm