Mary:  Just as with medications, chemical agents in the environment can
and do get into human milk in varying amounts depending on their
properties (e.g. lipid solubility, molecular weight, etc).  Workplaces
must by law provide employees with chemical safety data sheets, so she can
get these and find out more about the properties of these chemicals.
Another crucial issue is the degree of exposure she has.  If they are
volatile chemicals, does she wear protective equipment?  Was she allowed
to work during her pregnancy?  If so, baby got a lot more exposure in
utero.  If she is, indeed, exposed to the chemicals and they do, indeed,
get into her milk (it can be tested, if necessary), they may still not
pose any greater risk to the baby than having to switch to "that other
stuff" and its known risks.  By the way, lipid soluble toxins may not be
as harmful to the average breastfed baby, because bf babies, as a group,
tend to be leaner and therefore less likely to accumulate in fatty tissue.
Toxins which can adversely affect neurological development may be more
than made up for by all the marvelous brain-growth-producing stuff in
mother's milk. And let's not forget that abm, in addition to all its
known risks, is far from free of toxins, and it has to be mixed with water
which may contain its own set of nasty chemicals (like nitrites
and lead, which babies get full strength in abm, but only minute
if any amount in mother's milk regardless of mother's intake). Although
there are no easy answers here, it's important for the mother
to see that artificial feeding is not necessarily the "safer" alternative.
For a lovely summary on this topic, read the following:  Frank JW and
Newman J (Yes, our own Dr. Jack!).  Breast-feeding in a polluted world:
Uncertain risks, clear benefits.  Can Med Assoc J 1993;149:33-37.  Hope
this helps.  Alicia Dermer, MD, IBCLC.