Thimerosal
by author David Crowe

It comes as a surprise to many people that ethyl mercury in thimerosal is still an important preservative in flu vaccines, because the vaccines are prepared for multi-dose vials. Many are concerned that is the cause of recent increases in the number of cases of autism and other mental disorders.

Connection Proved

The link between thimerosal and autism was highlighted in a 2003 study reported in Experimental Biology and Medicine which compared adverse vaccine reports for another vaccine—used for diphtheria, tetanus, and pertussis (DTaP)—that was available with or without thimerosal. It found six times the rate of autism and mental retardation with the thimerosal vaccine and double the rate of speech disorders.

This research has been criticized for several reasons. The time period for the two vaccines was different (between 1992 and 2000 for the vaccine with thimerosal, but only between 1997 and 2000 for the vaccine without). Also, many people do not recognize or report adverse reactions, potentially leading to bias. However, most other adverse reactions were reported at a similar rate with both formulations, lending credence to the conclusion that thimerosal was responsible for increased reports of autism and mental retardation.

Another study listed 21 symptoms that occurred in both mercury poisoning and autism, a disease that was first identified only in 1943, less than 10 years after thimerosal was introduced into vaccines.

In Defence of Thimerosal

Some point to a Danish study of children between two and 10 years old who were diagnosed with autism between 1971 and 2000. It showed rates of autism climbing steeply after 1992 when thimerosal was removed from all vaccines, as proof that “vaccinations containing thimerosal do not increase rates of autism.” However, the Danish researchers noted several confounding factors. The definition of autism changed in 1994, there was heightened awareness of the condition, and information on outpatients was included in statistics for the first time in 1995. All these factors lead to an increase in autism reports that might have disguised declines due to the removal of thimerosal. Further, the researchers did not disclose that their institute is a major manufacturer of vaccines within Denmark.

Caution Recommended

The use of ethyl mercury-based thimerosal according to recommended vaccine schedules can cause the level of mercury in the body of infants to exceed US Environmental Protection Agency-recommended limits for an extended time in early childhood, especially between six months and two years.

Some children may be more susceptible to the effects of mercury, they may be allergic or hypersensitive to thimerosal, they may have a higher mercury burden at birth because of high levels in their mother, they may naturally clear mercury at a slower rate, or they may be injected with several vaccines at once. Mercury sensitivity may even have a genetic basis, leading to the false conclusion that the cause of similar disease in siblings is genetic rather than environmental.

Flu Vaccines a Source

The decline of thimerosal accelerated in 1999 when the American Academy of Pediatrics and the US Public Health Service jointly called for its removal from vaccines. However, it is still found in some vaccines commonly used in Canada, including flu vaccines, and much more extensively in vaccines used in developing countries. See our article on flu vaccines on page 72.

Parents who choose to vaccinate their children must be vigilant in ensuring that vaccines with thimerosal are not used. It is particularly immoral to continue the use of thimerosal in vaccines in third world countries.

How Deadly Can Mercury Be?

A health disaster in the 1950s and 1960s in Minamata, Japan, brought mercury poisoning to public attention. After chemical industries dumped increasing amounts of mercury into a nearby water source, thousands of people became mentally and physically incapacitated after consuming fish from this sources.

In 1969 Canada identified its own tragedy among residents of the Grassy Narrows Indian Reserve in northwestern Ontario, after a paper mill carelessly released mercury into the English and Wabigoon river systems.

Both health disasters involved methyl mercury, the organic form of the heavy metal that is easily absorbed by the body and well retained. Another form of mercury—ethyl mercury, the mercury used in thimerosal—is less toxic, but still seriously poisonous. Both types caused deaths in a series of poisonings in Iraq, where locals ate seed grain treated with mercury-based fungicides. Fatalities occurred with blood levels of ethyl mercury at about three times the blood level of methyl mercury.

Symptoms of Mercury Toxicity Include:

• delayed mental development
• numbness
• vision problems
• slurred speech
• involuntary shakes
• unconsciousness
• death

David Crowe is a Calgary-based environmentalist and medical science critic. Contact him through editorial@alive.com.

Source: alive #264, October 2004