Thiomersal


General
Systematic name	Ethyl(2-mercaptobenzoato-(2-)-O,S) mercurate(1-) sodium
Trivial names	Elcide Mercurothiolate Merfamin Merthiolade Merthiolate Mertorgan Merzonin Merzonin sodium Sodium ethylmercuric thiosalicylate Sodium merthiolate Thimerosal Thimerosalate Thiomersalate Vitaseptol
Molecular formula	C₉H₉HgNaO₂S
Molar mass	404.81 g/mol
Appearance	White or slightly yellow powder
CAS number	^*
EC-No	^*
Properties
Density and phase	500 kg/m³
Solubility in water	1000 g/l (20°C)
Melting point	232 - 233 °C (decomposition)
Boiling point	---
Basicity (pK_b)	---
Acidity (pK_a)	---
Thermodynamic data
Std enthalpy of formation Δ_fH°_gas	---
Standard molar entropy S°_gas	---
Hazards
EU classification	---
R-phrases
S-phrases
NFPA 704	---
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Regulatory data	Flash point, RTECS number, etc.
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Chemical infobox

Thiomersal (INN), commonly known in the United States as thimerosal, (C₉H₉Hg Na O₂S) is a mercury-containing (approximately 49% mercury by weight) organic compound (organomercurial) used as an antiseptic and antifungal agent. It was developed and registered under the trade name Merthiolate in 1929 by the pharmaceutical company Eli Lilly, and has been used as a preservative in vaccines, immune globulin preparations, skin test antigens, antivenoms, ophthalmic and nasal products, and tattoo inks.

The compound is being phased out for most childhood vaccinations in favor of single-dose vials.

Thimerosal causes susceptible bacteria to autolyze (break down their own cells with self-produced enzymes) via an unknown mechanism. In the body, it is metabolized to ethylmercury (C₂H₅Hg⁺) and thiosalicylate.

Material Safety Data Sheet

See Full Material Safety Data Sheet

Stability

Stable. May degrade in sunlight. Incompatible with strong acids, strong bases, strong oxidizing agents, iodine, heavy metal salts.

Toxicology

Poison. Experimental neoplastigen and teratogen. Harmful by inhalation and ingestion. May cause reproductive damage. May be harmful through skin contact. Typical OEL 0.05 mg/m³.

Chemical Hazard Symbol: T+ = Very toxic Criteria: Inhalation, swallowing, or absorption through the skin in very small amounts can cause considerable damage to health, and may sometimes be lethal. In the event of exposure serious evidence of severe, possibly irreversible damage to health by single, repeated, or prolonged absorption. MSDS Hazard Symbol T+

Chemical Hazard symbol: N = Dangerous for the environment Criteria: Liberation into aquatic and non-aquatic environments would present or may present immediate or delayed damage for one or more components of the environment. Precaution: Do not allow to enter sewerage systems, soil, or environment. Observe special disposal regulations. MSDS Hazard Symbol N

Personal protection

Safety glasses, adequate ventilation, protective clothing.
Risk Phrase: R 26/27/28-33-50/53

Very toxic by inhalation, in contact with skin and if swallowed. Danger of cumulative effects. Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.

Safety Phrase: S 13-28.1-36-45-60-61

Keep away from food, drink and animal feeding stuffs. After contact with skin, wash immediately with plenty of water. Wear suitable protective clothing. In case of accident or if you feel unwell, seek medical advice immediately (show the label where possible). This material and its container must be disposed of as hazardous waste. Avoid release to the environment. Refer to special instructions/Safety data sheets.

WGK: (Water Hazard Class): 3 - highly polluting substance.

Timeline

Early-1930s- first added to vaccines as a bactericide ^*.
Mid-1980s- used as a preservative in virtually all whole-cell DPT vaccines, which were routinely administered four times each to children before eighteen months of age, starting at two months.
Late 1980s- Hib vaccines are recommended for administration to children at eighteen months. They contain thiomersal.
Early 1990s- In the USA three doses of Hepatititis B vaccine (at that time containing Thiomersal) are recommended for infants under six months of age, beginning on the day of birth; four doses of Hib are recommended within an eighteen month period, beginning at age two.
Late 1990s- three of the vaccines included in Vaccination schedules for children between six and eighteen months of age contain thiomersal.
1999- The American Academy of Pediatrics requests removal of thiomersal from all pediatric vaccines.
2002- The USA Centers for Disease Control (CDC) and the USA Food and Drug Administration (FDA) state that: although thiomersal was to be discontinued in some paediatric vaccines, they would not be recalling any unused stocks, as they 'opinioned' that these stock presented no undue risk and that the change was purely cautionary.
2006- The World Health Organization, with US funding, is providing thiomersal-containing vaccines for children in developing countries with the same amounts of thiomersal as were given American children at their peak exposure levels. Current vaccination schedules give these in a shorter time period.

External links

Thiomersal Content of Vaccines Routinely Recommended for Children 6 Years of Age and Younger

See also: Geier, D.A., & Geier, M.R. (2006). Early downward trends in neurodevelopmental disorders following removal of Thimerosal-containing vaccines. Journal of American Physicians and Surgeons, vol. 11, pp. 8-13.

Mercury compounds | Carboxylic acids | Thiols | Lilly