Roles and Duties of a member of US congress.

http://www.wise-intern.org/orientation/documents/RL33686.pdf

Out of it:

...The U.S. Constitution establishes qualifications for Representatives
and Senators, but it is silent about the roles and duties of an individual
Member of Congress...

Even ir the duties of a member of parliament are not defined they can be
defined by what the functions of a government in general are..
One of them is to politically organize the entity of the country.
One important one is to serve the interests of the country and the
interests of the people in the country where this interests are involved
in their work.
This duties are inherent to the work of a government if it is defined
in a constitution or not.
I do not think it can be legal to neglect or ignore the interests of the
people of a  country for a member of government if it is in any way
feasible to do so.
One agency which frequently does so is the American FDA. It serves
with its policies industrial interests and not the interests of the people.
Further the congress with the approval of GMO related stuff,
because they are harmful to the people and the environment.
Is America strong enough to crackdown on their government for its
violations of duties in office?

I am not educated enough to follow this topic in detail and don't want
to spend that much time with it also. Maybe others pick this topic if
they believe the above mentioned worked out could
be helpful to put through more environmental protection or else.