How does mercury affect/effect fish?

Question

Hi,

I would like to know what are the affects/effects of mercury on fish?
And how does mercury get in the water (creeks, rivers, oceans,etc.)?

I would really appreciate if you could help me out and, where possible, give me the source.

Thanks (^_^)

Answer 1

Minamata Disease

Minamata disease was first discovered in Minamata city in Kumamoto prefecture, Japan in 1956. It was caused by the release of methyl mercury in the industrial wastewater from the Chisso Corporation's chemical factory, which continued from 1932 to 1968.

This highly toxic chemical bioaccumulated in shellfish and fish in Minamata Bay and the Shiranui Sea, which when eaten by the local populace resulted in mercury poisoning. As of March 2001, 2,265 victims had been officially recognised (1,784 of whom had died) and over 10,000 had received financial compensation from Chisso. Lawsuits and claims for compensation continue to this day.

A second outbreak of Minamata disease occurred in Niigata Prefecture in 1965. Both the original Minamata disease and Niigata Minamata disease are considered two of the Four Big Pollution Diseases of Japan.

EFFECT ON HUMANS

Minamata disease is a neurological syndrome caused by severe mercury poisoning. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision and damage to hearing and speech. In extreme cases, insanity, paralysis, coma and death follow within weeks of the onset of symptoms. A congenital form of the disease can also affect fetuses in the womb.

BACKGROUND

The Chisso Corporation first opened a chemical factory in Minamata in 1908. Initially producing fertilisers, the factory followed the nationwide expansion of Japan's chemical industry, branching out into production of acetylene, acetaldehyde, acetic acid, vinyl chloride and octanol, among others. The Minamata factory became the most advanced in all Japan, both before and after World War II.

The waste products resulting from the manufacture of these chemicals were released into Minamata Bay in the factory wastewater. Inevitably these pollutants had an environmental impact. Fisheries were damaged in terms of reduced catches and in response Chisso reached two separate compensation agreements with the fishery cooperative in 1926 and 1943.

The rapid expansion of the Minamata factory spurred on the local economy and as Chisso prospered, so did Minamata. This fact, combined with the lack of other industry, meant that Chisso had great influence in Minamata. At one stage over half of the tax revenue of Minamata City authority came from Chisso and its employees and the company and its subsidiaries were responsible for creating a quarter of all jobs in Minamata.

The Chisso Minamata factory first started acetaldehyde production in 1932, producing 210 tons that year. By 1951 production had jumped to 6,000 tons per year: over 50% of Japan's total output. The chemical reaction used to produce the acetaldehyde used mercury sulfate as a catalyst. A side reaction of the catalytic cycle led to the production of a small amount of an organic mercury compound, namely methyl mercury.[6] This highly toxic compound was released into Minamata Bay from the start of production in 1932 until 1968 when this production method was discontinued.

COMMENT

It very much looks like a case of unregulated control over industrial effluents and their effect on the environment. If Chisso was paying compensation to fishermen as far back as 1926 it was tacitly admitting that their presence in the area was not just a matter of boost for the local economy. That came at a price.

As to how much Chisso knew of the effects of mercury on fish and on humans and how early they knew this, it remains unclear. What is clear is that the company did not willingly co-operate with the investigation into the disease and did not furnish it with details of the chemicals they manufactured and the industrial processes involved.

It is a classic case of greed. The profit motive making industrialists oblivious to the effects of their industry on the people who liove around their plants.

Answer 2

Practically all fish contain some traces of mercury (and this was true even before people existed), some more than others. The levels of mercury are low enough that it really doesn't matter which fish you eat, but you should probably avoid eating very large amounts of one fish. The fish most likely to concentrate mercury are large fish, and these include tuna, swordfish, mackerel, and shark. Mercury is generally only an issue if you are pregnant or plan to become pregnant. Methylmercury from fish builds up over time if you eat a lot of fish that contain it, and then declines slowly over the course of many months if you stop, until it's gone. It's not really harmful to you, but high levels of methylmercury in your body can increase the likelihood of birth defects if you get pregnant. Here again, the risk is quite low, but if you don't want to take chances, don't eat tuna steaks five nights a week.

Answer 3

I've been told that our city water which comes from a lake has mercury, I use this water to fill my tropical freshwater fish tank. Is there any need to be concerned with the longevity and happiness of my fish?

Answer 4

It doesn't affect them directly as much as it does humans, perhaps because they don't live as long, and they are not as dependent on higher brain function as humans. But they accumulate it in their muscles.

It does work its way into creeks in some areas, especially mercury mines. It was used extensively in the processing of gold ore. Volcanic eruptions can release a large amount at one time. Industrial waste.

Answer 5

It's a health threat to both the fish and the people eating the affected fish.