High chemical levels found in robin eggs
by Greg Nelson
Results of a robin egg study in the St. Louis area was among the discussion topics during a recent meeting of the Pine River Superfund Citizens Task Force technical committee.
The data was released in a PowerPoint presentation by Michigan State University professor Dr. Matt Zwiernik, the director of the MSU Toxicology Lab, who has been overseeing the study of dead robins the past two years.
The egg study took place between May and August 2013.
Zwiernik’s team monitored 60 nests in the nine-block area near the former Velsicol Chemical plant site where remediation is now taking place, and other properties a few miles downstream from St. Louis.
Only 23 of the nests yielded eggs.
Abandoned nests and those with fewer than four eggs were not included in the analysis, task force Secretary Jane Keon said.
Like with results of the dead robin study, some of the DDx levels found in the eggs were “the highest ever recorded.”
Tissue concentration of DDx in the eggs from the nine-block residential neighborhood ranged from 57 to 770 parts per million with an average of 153 ppm.
DDx includes DDT, along with breakdown compounds of DDD and DDE.
The samples also found PBB ranging from 0.5 to 2.3 ppm.
In the eggs collected downstream DDx ranged from 1.1 to 4.3 ppm, with an average of 1.2 ppm, with PBB ranging from non-detectable amounts to 1 ppm.
No eggs hatched that had more than 63 ppm DDx, according to the report.
Researches monitored the nests twice a week and one or more eggs were taken from the 23 nests.
In the contaminated nine-block neighborhood the hatching rate ranged from a high of 21 percent to a low of 18 percent.
In another residential area in the city the hatching rate was between a high of 74 percent and a low of 47 percent.
Further downstream the hatching rate was from a high of 44 percent and a low of 33 percent.
As a comparison, the hatching rate of a nature park in Midland County ranged from a high of 94 percent and a low of 88 percent, according to the report.
Zwiernik, however, noted that robin eggs are not the best to study in the long grass areas of the downstream floodplain. He suggested using wren, sparrow or bluebirds for a more accurate result.
In the nine-block area near the former plant site, where more than 200 trees and contaminated soils are being removed, cleanup is being done to 5 ppm, but that might not be low enough, Zwiernik said.
He concluded that cleaning up to even 3 ppm DDx may still be too high of a concentration in the soil to protect the health of robins.
The Michigan Department of Environmental Quality plans to implement a long-term monitoring system in the neighborhood, Project Manager Dan Rockafellow said.
It will be done by looking at robin density, clutch size and fledgling success in that area of town.
Zwiernik recommended that the study take place for three consecutive years.