Assessment of Microscopic Pathology in Fishes Collected at Sites Impacted by Wood Tar in Pennsylvania

Open-File Report 2020-1024
Prepared in cooperation with the U.S. Environmental Protection Agency
By: , and 



In an effort to determine whether fish populations in an area affected by wood tar waste exhibited health effects, fish were collected and analyzed with histopathology. Multiple species, including Mottled Sculpin (Cottus bairdii), Creek Chub (Semotilus atromaculatus), White Sucker (Catostumus commersonii), Redside Dace (Clinostomus elongatus), Common Shiner (Luxilus cornutus), and Western Blacknose Dace (Rhinichthys obtusus) were sampled from a reference site, Meade Run, and potentially affected streams, Kinzua Creek and Threemile Run, in northwestern Pennsylvania. A full histopathological evaluation was conducted to identify microscopic abnormalities potentially associated with wood tar exposure. The evaluation identified primarily parasites associated with tissue changes. These included microsporidian parasites in the ovaries of Common Shiner and Western Blacknose Dace; myxozoan cysts in the muscle of Common Shiner, Creek Chub, and Western Blacknose Dace; trematode cysts in the muscle of Creek Chub, Redside Dace and Common Shiner; and coccidia in spleen or pancreas of Creek Chub and Common Shiner. Microscopic abnormalities potentially associated with chemical exposure included ceroid/lipofuscin deposits in the meninges of the olfactory lobe of the brain in Common Shiner, Western Blacknose Dace, and Creek Chub, as well as bile duct proliferation and a biliary tumor in Creek Chub. Overall, the findings did not reveal significant microscopic pathology consistent with exposure to wood tar waste.

Suggested Citation

Walsh, H.L., Blazer, V.S., Mazik, P.M., Sperry, A.J., and Pavlick, D., 2020, Assessment of microscopic pathology in fishes collected at sites impacted by wood tar in Pennsylvania: U.S. Geological Survey Open-File Report 2020–1024, 14 p.,

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Methods
  • Results
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Assessment of microscopic pathology in fishes collected at sites impacted by wood tar in Pennsylvania
Series title Open-File Report
Series number 2020-1024
DOI 10.3133/ofr20201024
Year Published 2020
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Leetown Science Center
Description vi, 14 p.
Country United States
State Pennsylvania
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details