Fish, Mercury and the Invisible Condition
The most pervasive physical handicap in America today is an invisible condition — hearing loss. Howard E. “Rocky” Stone. (1)
Today, hearing loss is the number one disability in the world, and approximately 28 million Americans, suffering some type of hearing loss, help fuel this statistic.
Of this number, only a few million are considered ‘deaf’ and the remainder are hard of hearing. In addition, 15 of every 1,000 people under the age of 18 have a hearing loss.
In a landmark study, ‘The Impact of Untreated Hearing Loss on Household Income,’ The Better Hearing Institute estimate that the annual cost in lost earnings due to untreated hearing loss is $122 billion, with the Federal government losing $18 billion in taxes.
This situation is not improving. ‘The Better Hearing Institute’ also reports that America’s hearing loss population is growing at a rate of 160% of the overall population growth.
Wow, that’s a pretty high growth rate.
What’s sustaining it? Is there an increase in older folk, or are there other influences at play?
Let’s take a closer look.
Anatomy of the Ear
Sound is collected by the pinna (the visible part of the ear) and directed through the outer ear canal. The sound makes the eardrum (tympanic membrane) vibrate, which in turn causes a series of three tiny bones; the hammer, the anvil, and the stirrup, (also known as the malleus), incus, and stapes in the middle ear to vibrate. The vibration is transferred to the snail-shaped cochlea in the inner ear; the cochlea is lined with sensitive hairs which trigger the generation of nerve signals that are sent to the brain.(2)
This image depicts stereocilia in the inner ear, and the resulting chemical reaction traveling down the pillar cells. Courtesy Mike Smith
The hair cells convert mechanical stimuli into electrical signals. Each has a characteristic organ-pipe array of giant microvilli (called stereocilia) protruding from its surface as rigid rods, filled with cross-linked actin filaments, and arranged in ranks of graded height.
That’s basically how sound is transmitted to the brain.
How does hearing loss occur?
Hearing loss can be divided into two basic types:
Conductive
Conductive hearing loss is the result of the interference of sound transmission from the outer ear to the inner ear. Common causes include, inner ear infections, accumulation of fluid in the middle ear, excessive wax, damage to the eardrum by infection or an injury, or otosclerosis. This type of hearing loss is temporary, and results in a less severe form.
Sensorineural
Sensorineural hearing loss is due to damage to the pathway from the hair cells of the inner ear to the auditory nerve and the brain. Common causes include, age-related hearing loss, injury to the inner ear hair cells as a result of trauma or noise, abnormal pressure in the inner ear, stroke, benign lesions, and brain tumors. (3)
It is injury to the pathway from inner hair cells to the auditory nerve and the brain that is of concern.
Why?
In humans and other mammals, the auditory hair cells, unlike olfactory neurons, have to last a lifetime. If they are destroyed by disease, toxins, or excessively loud noise, they are not regenerated and the resultant hearing loss is permanent. (4)
Warnings about damage from load noise at rock concerts and wearing of ear protection for excessive noise at the work place have often been voiced in the past. However, what has been less vocal are warnings about toxic degeneration of auditory hair cells .
Do we know of any toxic material capable of a degenerative effect on auditory cellular function?
One known toxic substance first came to light in Minamata, Japan, in 1956.
The substance in question was mercury.
Normally when inorganic mercury is released into the environment, a methylation process occurs which converts inorganic mercury to methyl mercury in the natural environment by the action of anaerobic organisms that live in aquatic systems including lakes, rivers, wetlands, sediments, soils and the open ocean.
In the past, methyl mercury was produced directly and indirectly as part of several industrial processes such as the manufacture of acetaldehyde. Currently there are few human sources of methyl mercury pollution other than as an indirect consequence of the burning of wastes containing inorganic mercury and from the burning of fossil fuels, particularly coal.(5)
The company responsible for the mercury enlightenment in Japan was the Chisso Corporation. It was caused by the release of methyl mercury in the industrial waste water 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 the mercury dumping continued, babies were born to contaminated mothers. The children were born with severe deformities, including limb deformities, mental retardation, deafness, and blindness. In 1956, researchers worked to find the source of the illness, which they termed ‘Minamata Disease’. It was obvious something was affecting the nervous system of the populous. One thing people in this fishing town had in common was that they all ate fish, so scientists suspected that the fish in Minamata Bay were being poisoned.(6)
Finally, in July 1959, researchers from Kumamoto University found that organic mercury was the cause of methyl mercury. It was later discovered that Chisso Corporation had dumped an estimated 27 tons of mercury compounds into Minamata Bay.(7)
In 2001, more than 30 years later, researchers presented evidence that the mercury poisoning of Minamata Bay in the 50’s and 60’s lasted longer, spread further, and affected tens of thousands more people than previously believed.
The study, by doctors at Kumamoto University, found that mercury damaged the central nervous system and impaired sight, hearing, smell, taste and touch when present at the level of just 10 parts per million in hair and umbilical cords. This is five times lower than the level recognized as harmful by the government.(8)
In humans, methyl mercury is rapidly transmitted throughout the body via the blood and readily enters cells and crosses the blood-brain barrier, as well as the placenta of pregnant women. On entering a hair cell, organic methyl mercury has the ability to revert back to inorganic mercury that does not readily cross cell membranes or the blood brain barrier and is responsible for the majority of toxicity effects. Inorganic mercury can remain in the cells of the nervous system for a very long time.
How does mercury affect the cells?
Mercury exposure causes significant changes in cell membrane permeability and axon capabilities in nerves. Organic mercury firstly affects peripheral nerves all over the nervous system. In peripheral nerves, pathological changes are selectively observed in sensory nerve fibers and are as follows: Swelling and degeneration of Schwann cells, noticeable changes in both myelin sheaths and axons.(9)
Myelin is a dielectric (electrically insulating) material that forms a layer, the myelin sheath, usually around only the axon of a neuron.
Miyakawa et al (1970) reported that most people who suffered from disease resulting from mercury poisoning in Japan suffered from sensory loss. This may be explained by damage to the myelin sheaths.
Myelin is essential for the proper functioning of the nervous system. The main purpose of a myelin layer (or sheath) is to increase the speed at which impulses propagate along the myelinated fiber. Unmyelinated fibers and myelinated axons of the mammalian central nervous system do not regenerate.
It is not difficult to speculate that if damage to the myelin layer occurs in the hair cell of the inner ear, and normal cellular chemical reactions are disrupted by the presence of mercury, then the interpretation of nerve signals received would be hard for the brain to facilitate.
“The problem is that the government has not launched a detailed epidemiological study,” said Shigeo Ekino, the professor who led the research. “They are afraid of looking into the wider area.”
The events that led to the Japanese poisoning occurred some 30 years ago.
What about today?
Today, although naturally occurring, some 2,000 tons of mercury enter the global environment each year from human-generated sources such as coal-burning power plants, incinerators and chlorine-producing plants.(10)
As in Japan, the primary way people in the United States are exposed to methyl mercury is by eating fish and shellfish. As we know, adverse health effects include damage to the central nervous system and the developing brains of young and unborn children are especially vulnerable.
Is this having an affect on children in the U.S.?
Each year in the United States, more than 12,000 babies are born with a hearing loss. The cause of hearing loss for many babies is not known, and hearing loss can go unnoticed for years. In the 2002/2003 school year, nearly 72,000 children ages 6 to 21 years got special education services under the ‘hearing impairment’ category.(11)
Is it hereditary?
It would not appear so when it is considered 9 out of every 10 children who are born deaf are born to parents who can hear.(12)
Are people still testing fish for contamination?
In Japan, scientists are concerned. Dolphin meat sold to the Japanese people is still highly contaminated with mercury, methyl mercury. However, the Japanese government provides no warning that eating dolphin meat poses a serious health hazard.
Is there just cause for concern?
Dolphin meat is found to be highly polluted, containing 19.2ppm (parts per million) of mercury. This is 48 times higher than the maximum advisory level of 0.4ppm, set by the Health, Labor and Welfare Ministry of Japan.
One package of dolphin meat showed as much as 5.69ppm of mercury, which is 14.2 times higher than the maximum advisory level. (13)
International teams of scientists working in Japan have analyzed hundreds of samples of whale and dolphin meat and reported their findings to the International Whaling Commission. They found that more than 90% of the samples exceeded limits for one or more pollutants. One sample had more than 1,600 times the permitted level of mercury. The average level of mercury was more than 5 times the maximum allowable level, while the average concentration of methyl mercury was four times the maximum level.
What about the States?
In February it was reported (HealthDay News) that tests on more than 300 samples of canned tuna from the top three brands in the United States revealed that more than half contained mercury levels above what’s considered safe by the Environmental Protection Agency (EPA).
Researchers from the University of Nevada, Las Vegas (UNLV), found that 55 percent of the samples had mercury levels higher than the EPA standard of 0.5 parts per million (ppm) and 5 percent had levels higher than the 1.0 ppm safety level set by the U.S. Food and Drug Administration (FDA) for commercially sold fish.
“Canned tuna accounts for up to a quarter of the nation’s seafood consumption and creates some significant regulatory challenges,”
study author Shawn Gerstenberger, an environmental and occupational health professor, said in a UNLV news release.
With pregnant women and children the most susceptible to mercury poisoning , yet also among the top consumers of canned tuna, federal agencies need to urge distributors to expressly state mercury levels in their products.
Many states have adopted EPA guidelines on tuna consumption, which suggest an average child consume only one can of tuna roughly every two weeks to ensure an acceptable level of mercury exposure.
What constitutes an acceptable level is any ones guess.
Any other evidence of the adverse health effects of mercury?
Researchers in Taiwan say they have established for the first time that the mercury compound present as a contaminant in some seafood can damage insulin-producing cells in the pancreas.
In their experiments, Shing-Hwa Liu and colleagues exposed cell cultures of insulin-producing beta cells to methyl mercury. They used concentrations of methyl mercury at about the same levels as people would consume in fish under the FDA’s recommended limits.
“Altogether, our data clearly indicate that methyl mercury-induced oxidative stress causes pancreatic beta-cell apoptosis (programmed cell death) and dysfunction,”
Why is this a problem?
The failure to make insulin or to respond to it constitutes diabetes mellitus. Insulin is made specifically by the beta cells in the islets of Langerhans in the pancreas. If the beta cells degenerate so the body cannot make enough insulin on its own, type I diabetes results. A person with this type of diabetes must inject exogenous insulin.
And guess what?
Based on the findings of the NIH study, five million Americans living with diabetes also have hearing loss that, in many cases, remains undetected and untreated,
said Dr. Cindy Beyer, audiologist and senior vice president of HearUSA.
Is fish consumption the only mercury source that could be affecting us?
For many years there have been concerns about mercury in dental fillings. However, the FDA issued a final regulation last July, saying that at the levels dentists use for tooth cavity filling, elemental mercury in dental amalgam does not harm patients.
That’s okay then.
Anything else?
Another common source of exposure has been identified. Thimerosal (TMS), a preservative found in many infant vaccines, contains 49.6% ethyl mercury (EtHg). As part of an ongoing review, the FDA announced in 1999 that infants who received multiple TMS-preserved vaccines may have been exposed to cumulative Hg in excess of Federal safety guidelines.(14)
Redwood et al looked at hair mercury concentrations in infants exposed to vaccinal TMS and found they are in excess of the EPA safety guidelines of 1 ppm for up to 365 days.
They stated:
‘more sensitive individuals and those with additional sources of exposure would have higher Hg concentrations.’
Given that exposure to low levels of mercury during critical stages of development has been associated with neurological disorders in children, including ADD, learning difficulties, and speech delays, the predicted hair Hg concentration resulting from childhood immunizations is cause for concern.
If all these health concerns give you an headache, don’t take a pill just yet.
Why?
Regular use of analgesics, specifically aspirin, NSAIDs, and acetaminophen, might increase the risk of adult hearing loss, particularly in younger individuals. Given the high prevalence of regular analgesic use and health and social implications of hearing impairment, this represents an important public health issue,
states Sharon G. Curhan, MD, ScM, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital, Boston.
Regular use of pain-relief medicine appears to increase risk of hearing loss, especially among middle-aged men, according to an American Journal of Medicine study. Researchers surveyed nearly 27,000 men every two years from 1986 to 2004; about one-fourth of the men said they had been diagnosed with hearing loss.
Men from 45 to 50 years old at the start of the study faced the greatest risk—a 33% increase for aspirin, 61% for ibuprofen and 99% for acetaminophen. Previous nonhuman research has found some substances in pain-relievers can decrease blood flow to the cochlea, the part of the inner ear that converts sound waves into brain signals.(16)
What can be done?
Well, based on the government’s inactivity, why not start up a hearing aid company?
As of September 30,2009, net domestic unit sales by manufacturers for the year were at an all-time high of 1,956,821; up by 111,953 (6.07%) from that date last year.
Not bad for an economic slump.
Hearing appliances range from $1000 – $2000, and are used by only one in four of the approx 28 million Americans with hearing loss. Maybe this is because they aren’t covered by insurance. One reason hearing aids are not covered is because of sheer numbers. With a 160% growth rate in hearing loss, you could make yourself a pretty penny if folk continue eating contaminated fish.
On the other hand, coal power plants and mercury in child vaccines could be taken out of circulation reducing mercury in the environment. Costs of hearing aids could be lowered and covered by the government so all folk suffering can have help.
These suggestions may be something the Government does not want to hear.
Maybe fish should be taken off the menu at the White House.
…………………………………………………………………………………………………………..
Help maintain ‘Heroin and Cornflakes’ by donating.
Your donation keeps us free of ads, and helps us continue to raise awareness on environmental, social and health issues.
Ann Margrain
Founder, ‘Heroin and Cornflakes’ blog.
…………………………………………………………………………………………………………..
