Lab fish exposed to a diabetes drug show few effects
Metformin is a pharmaceutical drug widely used to treat diabetes in humans by lowering glucose production and absorption. It is taken at doses of about 500–1000 mg daily and is excreted by the kidneys in urine.
Metformin can be degraded by microbes in sewage treatment plants but some of it passes through and ends up in our lakes and rivers. Metformin is one of the highest and most commonly detected pharmaceuticals in municipal wastewaters and in surface waters downstream of discharges.
Read this open access paper on the FACETS website.
Currently, we have little knowledge of whether this compound can affect fishes inhabiting rivers near discharges from wastewater treatment plants.
Fathead minnows are a common small fish that live in rivers and lakes across North America.
We wanted to assess the effects of exposure of fathead minnows to three concentrations of metformin (3, 31, and 322 µg/L) in a flow-through exposure (in the lab) over a full life cycle.
The low concentration we tested is like metformin concentrations in rivers, and the mid concentration is similar to metformin concentrations in wastewater effluents.
In this study, exposure of fish to metformin occurred throughout all the fish life stages: eggs, then larval fish and juveniles, then mature adults, and exposure continued through breeding.
The results of the 5.5-month exposure showed not many changes at all, except a delay in time to first breeding (but this did not affect the total number of eggs produced).
Overall metformin, at exposure concentrations similar to those found in the environment (3 and 31 µg/L), caused few negative effects in fathead minnows exposed for a life cycle.
This information will allow risk assessors to decide whether environmental concentrations of metformin are of concern to fishes that live in Canadian rivers and lakes near discharges from sewage treatment plants.
Read the paper — Fathead minnow exposed to environmentally relevant concentrations of metformin for one life cycle show no adverse effects by Joanne L. Parrott, Grazina Pacepavicius, Kallie Shires, Stacey Clarence, Hufsa Khan, Madelaine Gardiner, Cheryl Sullivan, and Mehran Alaee.
