J. Curt Pendergrass, Ph.D.; President, Affinity Labeling Technologies, Inc.

Thimerosal Synonyms (1,2)

(1,2) - (O-Carboxyphenyl)thio)ethyl mercury sodium salt; Elcide 75; Elicide; Ethyl(2-mercaptobenzoato-S)mercury sodium salt; O-(Ethylmercurithio)benzoic acid sodium salt; Ethylmercurithiosalicylic acid sodium salt; Ethylmerkurithiosalicilan Sodny (Czech); Ethyl (sodium O- ercaptobenzoato) mercury; Mercurothiolate; Mercury, Ethyl(2-Mercaptobenzoate-S)-, sodium salt; Merfamin; Merthiolate; Merthiolate salt; Merthiolate sodium; Mertorgan; Merzonin; Merzonin sodium; Merzonin, sodium salt; SET; Sodium Ethylmercuric Thiosalicylate; Sodium O-(ethylmercurithio)benzoate; Sodium Ethylmercurithiosalicylate; Sodium Merthiolate; Thimerosalate; Thimerosol; Thimersalate; Thiomerosal; Thiomersal; Thiomersalate

Thimerosal Physical & Chemical Properties (1,2)

• PHYSICAL PROPERTIES:
  Appearance: White powder with a faint yellow cast
  Molecular formula: C9H9HgO2SNa
  Formula weight: 404.8 (anhydrous)



• STABILITY / STORAGE AS SUPPLIED:
  Thimerosal should be stored at room temperature protected from light.
  It is reportedly stable in air but not in sunlight.



• SOLUTION STABILITY:
  The rate of oxidation of thimerosal in solution is greatly increased by traces of copper ions. In slightly acidic solution thimerosal may be precipitated as the corresponding acid which undergoes slow decomposition with the formation of insoluble products.



• SYNTHESIS: Thimerosal is made from the combination of ethyl mercuric chloride, thiosalicylic acid, sodium hydroxide and ethanol. Thimerosal Is Composed of Thiosalicylic Acid And Ethyl Mercury (1,2)

Concern About The Safety Of Thimerosal

• The Food and Drug Modernization Act (FDAMA) was enacted on November 21, 1997. Section 413 of the FDAMA is entitled "Food and Drug Administration Study of Mercury Compounds in Drugs and Food.



• The FDAMA required the FDA to (1) Compile a list of drugs and foods that contain intentionally introduced mercury compounds (e.g. mercurous chloride, mercuric chloride, phenylmercuric acetate, thimerosal), and (2) provide a quantitative and qualitative analysis of the mercury compounds in this list.

The Food And Drug Administration's Response To FDAMA (3)

• "The FDA is aware that mercury compounds (e.g. phenyl-mercuric acetate and thimerosal) are used as a preservative in OTC nasal solution products, prescription opthalmic drug products, and biological products including vaccines, immunoglobulins, antivenins, and skin test antigens."



• "Over 100 nasal spray/solutions, eye and topical products contain thimerosal-10 nose drop/spray products, 5 eye products, 2 ear products, 20 injectable products including toxoids, vaccines, antivenins."

By The First Grade Children In The U.S. Receive 21 Vaccinations,
Many Of Which Contain Thimerosal
Vaccines And Immunoglobulins Which Contain Thimerosal (4)

Birth: Hep B-first shot; 2 Months: DTaP-first; Polio-first; Hib-first; Hep B-second;
4 Months: DTaP-second; Polio-second; Hib-second;
6 Months: DTaP-third; Polio-third; Hib-third;
12 Months: Varicella-fist; MMR-first; Hib-fourth
15 Months: Hep B-third; DTaP-fourth
4 Years: MMR-second; Polio-fourth
5 Years: DTaP-fifth

Limiting Infant Exposure to Thimerosal in
Vaccines and Other Sources of Mercury (5)

• "Exposure to ethylmercury from vaccines containing thimerosal in the first 6 months of life ranges from 0 to 187 µg based on which vaccines are administered."



• "If all thimerosal containing vaccines are given, the total exposures exceed the EPA guidelines, and possibly other guidelines, for the smallest infants."



• "Clinicians are uncertain as to how much mercury can be safely given at 1 time when multiple thimerosal-containing vaccines are administered simultaneously."



• According to the Environmental Protection Agency, the average adult dose thought to be able to be consumed on a daily basis without harm is 0.1µg/kg per day.



• Could infants receiving multiple thimerosal containing vaccines during their first 6 months of life exceed this daily dose presumed to be safe by the EPA?
• 6 months x 30 days/month = 180 days; 187 µg ? 180 days = 1.04 µg/day
• The average 6 month old infant weighs 7 kg;; 1.04µg/day ? 7 kg = 0.15 µg/kg per day
• On the days when the vaccines are actually administered, the exposure is much higher

Joint Statement Of The American Academy of Pediatrics (AAP) and The Public Health Service (PHS) On July 7, 1999 Regarding The Use And Safety Of Thimerosal In Vaccines. (6)

• "The Food and Drug Administration (FDA) Modernization Act of 1997 called for the FDA to review and assess the risk of all mercury containing food and drugs. In line with this review, U.S. vaccine manufacturers responded to a December 1998 and April 1999 FDA request to provide more detailed information about the thimerosal content of their preparations which include this compound as a preservative."
  
  
• "Thimerosal has been used as an additive to biologics and vaccines since the 1930's because it is very effective in killing bacteria used in several vaccines and in preventing bacterial contamination, particularly in opened multi-dose containers. Some but not all of the vaccines recommended routinely for children in the U.S.contain thimerosal."



• "There is a significant safety margin incorporated into all the acceptable mercury exposure limits. Furthermore, there are no data or evidence of any harm caused by the level of exposure that some children may have encountered in following the existing immunization schedule."



• "Infants and children who have received thimerosal-containing vaccines do not need to be tested for mercury exposure.""The recognition that some children could be exposed to a cumulative level of mercury over the first six months of life that exceeds one of the federal guidelines on methyl mercury now requires a weighing of two different types of risks when vaccinating infants."



• "On the one hand, there is the known serious risk of diseases and deaths caused by failure to immunize our infants against vaccine-preventable infectious diseases; on the other, there is the unknown and probably much smaller risk, if any, of neuro-developmental effects posed by exposure to thimerosal.""The large risks of not vaccinating children far outweigh the unknown and probably much smaller risk, if any, of cumulative exposure to thimerosal-containing vaccines over the first six months of life."" Nevertheless, because any potential risk is of concern, the Public Health Service, the American Academy of Pediatrics, and vaccine manufacturers agree that thimerosal-containing vaccines should be removed as soon as possible."



• "Similar conclusions were reached this year in a meeting attended by European regulatory agencies, the European vaccine manufacturers, and the US FDA which examined the use of thimerosal-containing vaccines produced or sold in European countries."



• "The US Public Health Service and the American Academy of Pediatrics are working collaboratively to assure that the replacement of thimerosal-containing vaccines takes place as expeditiously as possible while at the same time ensuring that our high vaccination coverage levels and their associated low disease levels throughout our entire childhood population are maintained."

References

1. The Merck Index, 12th ed., p. 1590, #9451 (1996).

2. Martindale The Extra Pharmacopoeia, 30th ed., 804 (1993).

3. Federal Register, December 14, 1998, Vol. 63, 68775.

4. Seattle and King County Public Health Service Web Site

5. Neal A. Halsey, MD (1999). JAMA 282:1763-1766.

6. Morbidity and Mortality Weekly Report 1999; 48:563-565.