New York State
Yes, I know that you don't live in New York State. This is however the most useful and explanatory document that I have found on this matter and therefore linked it as further information.
Mercury Levels Tests are performed either with urine or with blood in the New York State.
The most commonly accepted methods of assessing mercury exposure are
to test urine or blood. Both tests usually measure levels of total
mercury (elemental, inorganic and organic).
- Elevated mercury in urine usually indicates exposure to an elemental or inorganic source
of mercury, such as from a job that uses mercury.
- Elevated mercury
in blood usually indicates exposure to organic mercury (such as from
eating fish containing methylmercury) or recent exposure to a high
level of elemental mercury vapor. For most people, an elevated blood
mercury level is associated with eating fish and other seafood
containing organic mercury.
(Source: New York Health Department)
In New York State, it is mandatory to report high level of mercury in blood or urine tests to the New York State Department of Health. Therefore, if anyone in New York had underwent a blood or urine test, they would have been notified if there are high mercury levels. (New York Health Department)
Massachusetts
It was a bit more challenging to find sources for Massachusetts. However, if one digs deep this is what I could find:
The Confidential Report Form for the State of Massachusetts states that all persons with mercury blood levels higher than 15 μg / L or urine mercury levels higher than 35 μg / g creatinine must be reported. (Link to the .doc version of the Confidential Report Form).
The Reporting Occupational Diseases and Injuries Form (again in .doc-type) states exactly the same.
The Public Health Fact Sheet Regarding Elemental Mercury Contamination at the Grafton Street School (MA) says that
[mercury] tests are available to measure elemental mercury levels in
the body.
Urine or blood samples are used to test for exposure to
elemental mercury. Urine is most useful for testing for potential
inhalation exposure to elemental mercury.
In order to get the most
accurate measure of mercury, the sample should be collected soon after
exposure.
Conclusion
Visit a GP of your choice and simply ask them to perform a mercury test on you. They will either collect blood or your urine and send it to a lab. If they perform a urine test and you are very very sure that you only want organic mercury to be checked (where it is recommended to do a blood test), kindly tell them exactly this.
I would strongly recommend printing out the linked PDF-Document and bringing that with you. It is easier for your doctor to accept the official document (and they will see that you are well-informed) than to trust in your reasoning.
Summary of References
New York State Health Department - Understanding Mercury Exposure Levels
Massachusetts Health Department - Confidential Report Form
Massachusetts Health Department - Reporting Occupational Diseases and Injuries Form
Massachusetts Health Department - Public Health Fact Sheet Regarding Elemental Mercury Contamination at the Grafton Street School