Connecticut Department of Energy & Environmental Protection

Fish Tissue Contaminant Monitoring Project

The DEEP Water Monitoring and Assessment Group routinely collaborates with the DEEP Fisheries Division and the CT Department of Public Health (DPH) Environmental Health Section (EHS) to assess fish tissue contamination in Connecticut.  This collaboration maximizes the benefit of limited available resources and provides for the collection and analysis of data that is mutually beneficial to both programs.  DEEP utilizes the data to assess water quality concerns, while DPH EHS reviews the data and then conducts risk assessment on those concentrations to help inform whether fish consumption advisories are needed.

Program History
PFAS Investigations
Mercury Investigations
U.S. EPA National Rivers and Streams Assessment
Lead Investigations
Chlordane Investigations
PCB Investigations
Radiation in Fish Tissue Study
Algal Toxin (Microcystin) Study

Program History

Monitoring of toxic contaminants in tissues of fish and invertebrates has been conducted by DEEP since the late 1970s.  Efforts have historically included analysis of levels of contaminants related to industrial activities, including mercury (Hg), lead (Pb), and polychlorinated biphenyls (PCBs).  More recent work has sought to study new contaminants of emerging concern, such as per- and polyfluorinated alkyl substances (PFAS).

Additional data collection has occurred in Connecticut in response to site specific releases and as part of larger regional US EPA-led studies.

PFAS Investigations

Per- and polyfluorinated alkyl substances, or PFAS, are a group of thousands of manmade chemicals that have been used widely in consumer products and industry since the 1940s. Due to their unique chemical structure, PFAS are extremely stable and repel oil, grease, water, and heat. Unfortunately, these same properties that make PFAS desirable for industrial processes, also make them extremely resistant to breaking down in the environment (i.e., 'persistent'), earning them the nickname “Forever Chemicals.”

PFAS easily migrate in the environment and cause contamination of soil, sediment, groundwater, and surface water.  Since PFAS are not currently known to be broken down by natural processes, they could persist in the environment indefinitely, earning them the nickname “forever chemicals.” As such, humans and animals can be exposed to PFAS through exposure pathways such as drinking contaminated water and eating contaminated fish and plants.

Therefore, in 2019, CT DEEP collaborated with CT DPH and other state agencies to develop a PFAS Action Plan for the State. One of the key recommended actions of the plan was to assess food-related PFAS exposure pathways, including fish and shellfish, to minimize Connecticut residents' PFAS exposure.  

To learn more about DEEP PFAS surface water investigations visit the PFAS Surface Water and Fish Tissue Monitoring webpage.

Mercury Investigations

Mercury is a naturally occurring heavy metal that can accumulate in living tissue.  Mercury is introduced into the environment though both natural and human facilitated activities. Unfortunately, exposure to mercury causes a variety of health issues. Pre-natal exposure is of particular concern as it can cause issues with neuro-development.  Fish consumption is one of the primary means of mercury exposure in humans. 

Given these concerns, DEEP partnered with the Connecticut Institute of Water Resources in the mid 1990s to conduct a study to evaluate ambient mercury concentrations in Connecticut lakes and ponds. Between 1996 and 1997, fish were collected from 56 different waterbodies throughout the state. The study confirmed that mercury levels in fish tissue were elevated and that non-point sources such as atmospheric deposition play a key role in mercury concentrations within Connecticut waterbodies.  In order to protect the public, a statewide fish advisory consumption was put in place .

The statewide lakes study was repeated again in 2005-2006 by the University of Connecticut with funding from DEEP. Results from this study were encouraging, demonstrating that mercury levels in Connecticut fish tissues are declining on a statewide basis. However, contamination levels still commonly exceeded threshold levels used to establish the statewide consumption advisory.

A third round of study was completed in 2022.  DEEP provided funding to the New England Interstate Water Pollution Control Commission (NEIWPCC) and the University of Connecticut to collect tissue samples from all lakes included in the original study. The overall conclusion of the study is that mercury concentrations in largemouth bass are declining through time, but less so recently.  Individual fish with high mercury concentrations (≥0.3 ug/g) still exist, particularly in the eastern half of Connecticut.  

Ongoing repetition of this study, at approximately ten-year intervals, is planned (funding permitting) to continue to evaluate trends in mercury contamination across the state.

Special Projects

In addition, to the ongoing assessment of mercury in Connecticut fish tissue, the Agency conducts project-specific fish tissue contaminant monitoring as needed and as funding is available.  Such monitoring supports national research efforts as well as evaluation of evaluate tissue contaminant levels associated with source of contamination, such as an industrial spills. 

U.S. EPA National Rivers and Streams Assessment (NRSA)

The DEEP Water Monitoring Program participates every five years in the National River and Stream Assessment (NRSA) component of the EPA’s National Aquatic Resource Surveys (NARS). NARS is a collaborative program between EPA, states, and tribes to assess the quality of the nation’s rivers and streams, as well as coastal waters, lakes and ponds, and wetlands. The NRSA is a national probability-based survey of rivers and streams based on physical, chemical and biological data collected and analyzed using standardized field and laboratory methods by state, EPA and contractor crews across the USA.  Each cycle, a subset of NRSA sites are flagged for tissue sample collection.  Samples are analyzed by EPA-contracted labs for mercury, PCBs and, more recently, PFAS.  Associated reports and results can be downloaded from the EPA National River and Stream Assessment webpage. 

Lead Investigations

Lead is a naturally occurring element found in small amounts in the environment. While it has some beneficial uses, it can be toxic to humans and animals, causing health effects. Lead and lead compounds have been used in a wide variety of products found in and around our homes, including paint, ceramics, pipes and plumbing materials, solders, gasoline, batteries, ammunition and cosmetics. Lead may enter the environment from these past and current uses. Lead can also be emitted into the environment from industrial sources and contaminated sites.

CT DEEP efforts to evaluate lead in aquatic tissue, have included an investigation of lead in the tissue of Blue Crab collected from the lower Mill River in Fairfield, CT.  For several decades the Exide Corporation operated a battery manufacturing plant on the bank of the river. The discovery of lead in river sediment samples collected from the area prompted concern regarding the safety of consuming blue crab collected in the area near the former battery plant. Between 1999 and 2000 crabs were collected and analyzed; results indicated lead levels were indeed elevated in the tissue and hepatopancreas of the animals.  Therefore, in order to protect public health, the Department of Public Health (CT DPH) issued a 'do not eat' consumption advisory for any crabs collected from the river between Harbor Road and Sturges Road in Fairfield, CT. Between 2005 and 2013, an extensive remediation effort occurred at the former Exide Corporation site, including dredging and disposal of contaminated sediments. Post-remediation monitoring results confirmed a substantial decline in the lead sediment levels in the area. After several failed attempts, in 2022, CT DEEP staff successfully collected blue crab from the lower Mill River in Fairfield for analysis. Preliminary results indicate that lead levels appear to have declined in blue crabs residing in the area. CT DPH is evaluating these results in order to determine whether the crab consumption advisory for the area can be modified or removed. 

Chlordane Investigations

Chlordane, a chlorinated cyclodiene, was manufactured in the United States beginning in the late 1940s as a multipurpose insecticide. From the early 1940s to the late 1980s, chlordane was used extensively in home and agricultural applications in the United States for the control of termites and many other insects. It has since been classified as a human neurotoxicant and, after an initial phase-out, all uses were completely banned in 1988 (US EPA 2000).  

In 1995, discovery of elevated chlordane levels in white catfish collected from Brewster Pond in Stratford, CT, resulted in the issuance of a fish consumption advisory for the pond. The advisory remains in effect and CT DPH advises the public to not eat catfish or bullheads collected from the pond.   

In 1998, the University of Connecticut (UConn) Environmental Research Institute (ERI) carried out a statewide investigation of total chlordane, total DDT and total PCBs levels in fish tissue from Connecticut lakes and ponds. As a result of this work, a fish consumption advisory and water quality impairment was issued for Union Pond in Manchester, CT.  In 2022, tissue analysis of bass and carp collected from Union Pond indicated that chlordane levels in fish tissue have decreased dramatically; these data are currently under review by DEEP and DPH to determine whether modifications to the water quality impairment and/or fish consumption advisory may be warranted. 

Polychlorinated Biphenyls (PCBs) Investigations

PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons. PCBs were manufactured in the United States from 1929 until manufacturing was banned in 1979. They have a range of toxicity and have been demonstrated to cause a variety of adverse health effects including cancer. Over the years, several investigations have sought to understand PCB levels in Connecticut fish tissue.  Reports and data associated with the most recent PCB investigations, which occurred in the Connecticut River and Long Island Sound, are provided below.  Please contact the program coordinator for additional details. 

Radiation in Fish Tissue Study

In 2017, Fisheries Division and Water Monitoring Unit staff provided field support to the Air Bureau’s Radiation Division to assess fish tissue contamination in the Pequabuck River (Bristol, CT).  The proposed monitoring location was adjacent to the site of a former clock factory, which used Radium-226 from the mid to late 19th to mid-20th century. Radium contamination was discovered in soil and sediment samples at the site and the Radiation Division sought to determine whether the fishery in the adjacent stretch of river was also affected. In July 2017, the stretch of river adjacent to the site of concern was successfully monitored and several fish were collected for analysis. Based upon these data, it was determined that radium levels in fish at that site are not a public health concern.

Algal Toxin (Microcystin) Study

With the increasing prevalence of harmful algal blooms (HABs), there is interest in determining the relationship between blooms and algal toxin levels in fish tissue. Algal toxins are toxic substances released by some types of algae when they are present in large quantities (HABs) and decay or degrade.  While many varieties of algal toxins exist, one that is of particular concern is microcystin. Microcystin is a potent liver toxin and possible human carcinogen.  In 2018, DEEP staff sought to collect fish from a waterbody that experiences chronic HABs to evaluate the microcystin levels in the fish tissue. CT DEEP staff initially identified Lake Zoar as an ideal candidate for collection, but high flows during 2018 prevented collection.  Bantam Lake in Litchfield County, a location also known to experience annual HABs, was identified as an alternative sampling site.  Fish were collected from Bantam Lake in October 2018, during the occurrence of a bloom, and submitted to the U.S. EPA Office of Research and Development (EPA ORD) for analysis. Species collected included largemouth bass, chain pickerel, northern pike, tench, golden shiner, and banded killifish. Results were encouraging, as all of the Bantam Lake fish tissue analyzed were nondetect for micrycystin. 

Related Pages

Program Contact Information

Water Monitoring and Assessment Program
79 Elm Street, Hartford CT 06106
DEEP.watermonitoring@ct.gov

   
   

Content last updated October 25, 2023