Page 20 - Spring2018

No regulatory offers some protection against mercury and is cantly higher than the EPA’s “safe” reference

safety found in fish as well as other foods. dose of 0.3–0.6 micrograms total per day for
methylmercury exposure in infants. Moreover,
standard VACCINES the EPA safe reference dose for methylmercury
exists for One of the most controversial aspects sur- may be too lax, 24,25 especially when applied to
ethylmercury. rounding vaccines is their mercury content. ethylmercury. Indeed, there may be no thresh-
Prior to about 2004, many childhood vaccines old that precludes adverse neuropsychological
contained thimerosal, a preservative and adju- effects in children, 24,26 whose brains are rapidly
vant that is 50 percent ethylmercury. Childhood developing. Furthermore, unlike methylmer-
exposure to thimerosal rose sharply in the U.S. cury ingested from fish, injected ethylmercury
during the 1990s as the U.S. Centers for Disease is not subject to the natural defense mechanisms
Control and Prevention (CDC) added new vac- related to ingestion, including metallothioneins
cines to the childhood vaccine schedule. Infants and selenium.
strictly adhering to the CDC vaccine schedule In 1999, the U.S. Public Health Service
during this time typically received up to 187.5 called for the elimination of thimerosal from
micrograms of mercury in the first six months of childhood vaccines. Due to supply and demand
life alone. As shown in Table 2, this was from issues, it took several years to transition to
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three doses each of the diphtheria-tetanus-acel- reduced-thimerosal and then thimerosal-free
lular pertussis (DTaP), Haemophilus influenzae alternatives. However, during the period
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type b (Hib), and hepatitis B (HB) vaccines, with in which thimerosal began to be phased out
additional doses of DTaP and Hib given later. 23 of other pediatric vaccines, the thimerosal-
No regulatory safety standard exists for containing influenza vaccine became an im-
ethylmercury. However, because ethylmercury portant new source of mercury exposure for
is chemically similar to methylmercury (the fetuses and children. This is because the CDC
form of mercury present in dietary fish), we began recommending in 2002 that the influenza
can compare the 187.5-microgram ethylmercury vaccine be given to children aged six months
dose to the safe reference dose for methylmer- to twenty-three months, as well as pregnant
cury set by the EPA. This reference dose is 0.1 women in their second and third trimesters,
microgram per kilogram of body weight per even though the only vaccine approved for these
day for chronic exposure, equivalent to about groups at the time was preserved with thimero-
0.3 micrograms per day for a newborn and 0.6 sal. Next, the CDC aggressively increased the
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micrograms per day for a six-month-old baby. dosing and expanded the target groups for the
Averaging the 187.5-microgram exposure (ac- influenza vaccine, recommending a double
tually delivered in a number of concentrated dose for infants at both six and seven months,
doses) over the six-month period, the resulting plus subsequent annual doses, and a dose for
dose of 1.04 micrograms per day is signifi- all pregnant women, no longer limited to the

TABLE 2: MERCURY CONTENT (IN MICROGRAMS) OF
1990S-ERA CHILDHOOD VACCINES RECOMMENDED
DURING THE FIRST SIX MONTHS OF LIFE

Vaccine Number of Doses in Total Mercury Content (and
the First Six Months Amount per Dose) 23
Diphtheria-tetanus-acellular pertussis (DTaP) 3 doses* 75 micrograms (25 mcg per dose)
Haemophilus influenzae type b (Hib) 3 doses* 75 micrograms (25 mcg per dose)
Hepatitis B (HB) 3 doses 37.5 micrograms (12.5 mcg per dose)
TOTAL 9 doses 187.5 micrograms

* With a fourth dose given after six months of age, for a total of 100 micrograms each for DTaP and Hib across the four doses.

18 Wise Traditions SPRING 2018