Abstract:
The number and volume of chemicals around us have increased significantly since
industrialization. The main challenge in ecotoxicity is to accurately identify and
distinguish the risks of tens of thousands of chemicals on aquatic life. We put forward
a new approach to estimate median lethal concentrations (LC50) of organic compounds
by establishing target passive sampler models. In this study, we demonstrated that
passive samplers are good proxies for the bio-membranes in organisms. Hence, passive
samplers can be substituted in the target lipid model to predict the reliable baseline
toxicities of chemicals accumulated on passive samplers. Our new approach sheds light
on the mode of toxic actions of organic chemicals. We evaluated and categorized four
types of passive samplers viz., polyacrylic (PA), polyethylene (PE),
polydimethylsiloxane (PDMS) and polyoxymethylene (POM). The analyses showed
that PA works well for most of the chemical groups such as baseline compounds.
However, for a few chemical groups such as aldehydes and alpha, beta unsaturated
ketones, the PDMS displayed a good agreement between estimated and experimental
values. Our approach worked well for fish but showed significant systematic deviations
from experimental values for daphnia. Further investigation indicated that the
assumption of a critical burden of 100 mmol/kg in bio-membrane is suitable for fish but
needs to be revisited for daphnia. The predictive performance of our new approach is
at par with previous approaches. However, our method is simple and offers the
opportunity of interfacing the measurement of environmental levels of organic
pollutants with modeling of LC50 values of those chemicals.
