It's going to depend upon the type of
plastic you're using, as they're
composed of different chemical
compounds. If you look at the bottom
of your plastic cup (or dish, etc),
there's normally a recycling symbol
and a number. The number classifies
the type of plastic it is.
You can find the plastic classification
numbers here.
My opinion as an environmental
chemist: if your drink cup is #2, #4 or
#5, then your risk of exposure is low
enough to not be an issue, as these
classes of plastics do not normally
contain bisphenol A (BPA) or
phthalates.
You should not be using #3 (polyvinyl
chloride aka PVC) for anything food
related; they contain bisphenol A and
phthalates; both of which are
endocrine disruptors.
No. 6 is fine for storing foods, but you
should not reheat foods in
polystyrene. No. 7 is a 'catch all' for
plastics - some of these can contain
BPA.
It is nearly impossible to be
completely BPA/Phthalate free; they're
nearly ubiquitous in our lives: plastic
wrap, the coating inside your canned
beans, etc.
There are reports which suggests that
BPA causes cancer , and there are
many published studies regarding
phthalates impacting sperm count
and quality . BPA has been tentatively
linked to premature on set of puberty.
Before you run off and throw out
everything plastic in your house, you
need to understand that you're
exposed to BPA from more than just
leaching from your drinking bottles &
cups. BPA will degrade rapidly in air
but it persists in water - this means
that you're potentially exposed to BPA
via your drinking water (if it's a public
water supply) or through what you eat
(fish) since BPA is both
bioaccumulated and biomagnified.
So yes, there is a risk of BPA/phthalate
leaching from your cup (or container)
to your water (and thus into you),
however the amount leached is most
likely very small. In most of the studies
where laboratory rats developed
cancer , they were receiving large
(1000-10000 ppm) doses of BPA
through their food, or via
subcutaneous injections.
It's why they pushed to have BPA and
phthalates removed from baby
bottles (which are still normally
marked with a 7 code!) - there was a
higher risk of BPA/Phthalate exposure
to infants, who are normally given
their milk warm. Higher dose given +
consistent exposure = increased risk.
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