The Duval County Department of Health is slated to issue a fish-consumption advisory on July 5, notifying residents of elevated levels of potentially harmful chemicals found in two tributaries near Jacksonville’s downtown urban core: Hogan’s Creek and Longbranch.

Following concerns from area residents, the federal Environmental Protection Agency collaborated with the department to collect samples and test the fish. What they found are high levels of mercury and PCBs, among other dangerous chemicals. The Department of Health says that it is waiting for further information before it officially makes an announcement concerning the discovery, but that there is “no immediate health threat” in consuming the fish.

The affected fish, which include largemouth bass, striped mullet and blue tilapia, contain a host of seemingly un-pronouncable chemicals, including the following:

• Dieldrin: a highly poisonous pesticide that is currently banned in the U.S. (Exposure to dieldrin, such as from eating contaminated fish, can affect the nervous system.)
• Chlordane and heptachlor: pesticides used in U.S. agricultural practices from the 1950s until the 1980s.
• Dioxin: a highly toxic chemical contaminant often formed during waste incineration
• Inorganic arsenic: a semi-metallic element (.pdf) that can be emitted into air and then deposited into water and soil during industrial operations.

Hogan’s Creek, which is located near downtown Jacksonville, has a long history of environmental contamination.

According to a 2010 Florida Times-Union article, an area near the creek once housed a plant where coal was converted into gas. Some of the plant’s by-products are thought to have leached into the creek, contaminating the groundwater with potentially cancer-causing coal tar.

“Coal tar pollution has been identified in that area since at least 1993, when a city-financed study for a stormwater project reported contamination in soil and in sediment in the creek,” wrote the Times-Union‘s Steve Patterson. Talks to label the land along the creek a “Superfund” site, which would put the federal EPA in charge of repairing the damage, never fully materialized.

Mercury is often found in coal-derived materials, and is especially hazardous for pregnant women, children and the elderly. PCBs (or Polychlorinated Biphenyls), also derivatives of coal, have been proven to cause cancer in animals and are a probable source of cancer in humans.

A source, who wished to remain anonymous, says that the department was initially going to hold off on its release until July 13, but several calls from concerned residents warranted more attention.

A Duval County Department of Health representative said that the chemicals are “normal stuff found in pesticides,” but “at an elevated level.” The department maintains that there is no immediate health threat for fish consumed in either of the tributaries, and that any potential threat would be brought on by long-term consumption of the affected species.