By Kent Gray

Triplicate staff writer

A trace amount of a controversial preservative found in a Del Norte County vaccine is minute and not cause for alarm, according to local health officials.

The preservative, thimerosal, is an ingredient in the county's hepatitis B vaccine, called Engerix B. The preservative has been under fire by critics for decades because it contains ethyl mercury, allegedly linked to neurodevelopmental disorders and autism in children.

Public Health Officer Dr. Warren Rehwaldt said of approximately seven vaccines in the county, only the hepatitis B vaccine contains any thimerosal, and it only has a ‘trace amount.'

"Most of the formulas have been improved in recent years and exclude (thimerosal)," Rehwaldt said. "The risk of consequences from diseases that vaccines prevent is still much higher than risks from vaccines and their contents."

Thimerosal critics cite tests for methyl mercury, a different form of mercury proven to have a toxic effect on humans, as evidence against thimerosal.

The Food and Drug Administration, the Center for Disease Control and the Institute of Medicine all claim laboratory tests are inconclusive linking ethyl mercury to neurodevelopmental disorders. The Institute of Medicine's Immunization Safety Review Commission, however, concluded it is still best for infants and pregnant women to avoid any form of mercury.

"Full consideration (should) be given to removing thimerosal from any biological product to which infants, children and pregnant women are exposed," the commission said in its findings.

The FDA, however, concluded that a ‘trace amount' of ethyl mercury, and even methyl mercury, in vaccines is within safe limits for humans. A ‘trace amount' is less than one microgram per one-cubic-centimeter dose of vaccine. This is equivalent to the amount found in Engerix B in Del Norte County.

Congressman Dan Burton (R-Ind.) is leading a legislative charge against thimerosal in Washington. Aside from calling for a recall of the product, Burton is sponsoring adding the preservative to the National Vaccine Injury Compensation Program list for individuals claiming injury from childhood immunizations.

"We cannot in good conscience leave thimerosal-containing vaccines on the shelf until used up, potentially exposing our children to chemicals that may lead to neurodevelopmental disorders. Mercury is toxic to the human body," Burton said last year." "... I am asking every doctor, every health clinic, and every facility that provides childhood immunizations to check your vaccine supplies and return all thimerosal-containing vaccines and request thimerosal-free vaccines."