3,555 research outputs found
Estrogenic chemicals often leach from BPA-free plastic products that are replacements for BPA-containing polycarbonate products
Background: Xenobiotic chemicals with estrogenic activity (EA), such as bisphenol A (BPA), have been reported to
have potential adverse health effects in mammals, including humans, especially in fetal and infant stages. Concerns
about safety have caused many manufacturers to use alternatives to polycarbonate (PC) resins to make hard and
clear, reusable, plastic products that do not leach BPA. However, no study has focused on whether such BPA-free
PC-replacement products, chosen for their perceived higher safety, especially for babies, also release other chemicals
that have EA.
Methods: We used two, well-established, mammalian cell-based, assays (MCF-7 and BG1Luc) to assess the EA of
chemicals that leached into over 1000 saline or ethanol extracts of 50 unstressed or stressed (autoclaving,
microwaving, and UV radiation) BPA-free PC-replacement products. An EA antagonist, ICI 182,780, was used to confirm
that agonist activity in leachates was due to chemicals that activated the mammalian estrogen receptor.
Results: Many unstressed and stressed, PC-replacement-products made from acrylic, polystyrene, polyethersulfone, and
Tritanâ„¢ resins leached chemicals with EA, including products made for use by babies. Exposure to various forms of UV
radiation often increased the leaching of chemicals with EA. In contrast, some BPA-free PC-replacement products made
from glycol-modified polyethylene terephthalate or cyclic olefin polymer or co-polymer resins did not release chemicals
with detectable EA under any conditions tested.
Conclusions: This hazard assessment survey showed that many BPA-free PC- replacement products still leached
chemicals having significant levels of EA, as did BPA-containing PC counterparts they were meant to replace. That is,
BPA-free did not mean EA-free. However, this study also showed that some PC-replacement products did not leach
chemicals having significant levels of EA. That is, EA-free PC-replacement products could be made in commercial
quantities at prices that compete with PC-replacement products that were not BPA-free. Since plastic products often
have advantages (price, weight, shatter-resistance, etc.) compared to other materials such as steel or glass, it is not
necessary to forgo those advantages to avoid release into foodstuffs or the environment of chemicals having EA that
may have potential adverse effects on our health or the health of future generations.This work was supported by the following NIH/NIEHS grants: R44 ES011469,
01–03 (CZY); 1R43/44 ES014806, 01–03 (CZY); subcontract (CZY, PI) on
an NIH Grant 01–03 43/44ES018083-01 to PlastiPure (DK, SY PIs).Neuroscienc
Entropic Priors and Bayesian Model Selection
We demonstrate that the principle of maximum relative entropy (ME), used
judiciously, can ease the specification of priors in model selection problems.
The resulting effect is that models that make sharp predictions are
disfavoured, weakening the usual Bayesian "Occam's Razor". This is illustrated
with a simple example involving what Jaynes called a "sure thing" hypothesis.
Jaynes' resolution of the situation involved introducing a large number of
alternative "sure thing" hypotheses that were possible before we observed the
data. However, in more complex situations, it may not be possible to explicitly
enumerate large numbers of alternatives. The entropic priors formalism produces
the desired result without modifying the hypothesis space or requiring explicit
enumeration of alternatives; all that is required is a good model for the prior
predictive distribution for the data. This idea is illustrated with a simple
rigged-lottery example, and we outline how this idea may help to resolve a
recent debate amongst cosmologists: is dark energy a cosmological constant, or
has it evolved with time in some way? And how shall we decide, when the data
are in?Comment: Presented at MaxEnt 2009, the 29th International Workshop on Bayesian
Inference and Maximum Entropy Methods in Science and Engineering (July 5-10,
2009, Oxford, Mississippi, USA
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