A better alternative to phthalates?

Date:
September 25, 2020
Source:
National Institute of Standards and Technology (NIST)
Summary:
Researchers analyzed urine samples from pregnant women
to look for the presence of DINCH, which is short for
di(isononyl)cyclohexane-1,2- dicarboxylate. They found
concentrations of DINCH in most of the urine samples but no evidence
of effects in lab assays on two hormones, progesterone and estrogen.



FULL STORY ========================================================================== Detergents, shampoos, soaps and other everyday items sometimes contain
a group of chemicals called phthalates, which are often used to enhance products and add flexibility to plastics. However, mounting research
has shown a link between phthalates and effects on hormones in humans, laboratory animals and wildlife, which is why phthalates are increasingly
being replaced with other chemicals, such as a compound called DINCH.


==========================================================================
In collaboration with the Medical University of South Carolina,
researchers at the National Institute of Standards and Technology (NIST) analyzed urine samples from pregnant women to look for the presence of
DINCH, which is short for di(isononyl)cyclohexane-1,2-dicarboxylate. They
found concentrations of DINCH in most of the urine samples but no evidence
of effects in lab assays on two hormones, progesterone and estrogen. The researchers have published their findings in the journal Chemosphere.

Phthalates are often called plasticizers and can be found not only in
personal care products to help them maintain a gel-like consistency but
also in garden hoses, inflatable toys and medical tubing. "They are
used to provide flexibility in plastics. Think of a rubber ducky and
how squishy it is. That's because of phthalates in vinyl," said NIST
researcher John Kucklick.

However, phthalates can disrupt the hormonal or endocrine system, which
may cause pregnancy loss, infertility and harmful effects on the delivery
of a baby.

As a result, many manufacturers have replaced phthalates with chemicals
such as DINCH, another type of plasticizer, but less is known about
the effects of this chemical compound on humans. DINCH has been used
since 2002 in commercial products such as toys, medical devices and
food packaging.

"People are exposed to different compounds, and we find out about some of
them, such as phthalates, which are being replaced by industry," said NIST researcher Jessica Reiner. "We may or may not know a lot of information
about these new compounds, but studies like this one are always looking
to understand if they're a good substitute compared with other ones."
Once DINCH enters the human body, it is processed and broken down into compounds called metabolites and excreted in the urine. The researchers collected urine samples over a period of four years from a total of
100 pregnant women living in the Charleston, South Carolina, area who
planned to deliver at the Medical University of South Carolina medical
center. The samples were then analyzed to check for DINCH metabolites.



========================================================================== Plasticizers are found everywhere, and it is challenging to measure the compound by itself because of all the possible contamination sources in
the lab. "So, we look at the metabolites that have gone through a person,
and they're only found in urine and not found anywhere else. It's much
easier to measure than the unmetabolized compound," said Kucklick.

At the Hollings Marine Laboratory in Charleston, NIST researchers analyzed urine samples for three DINCH metabolites using liquid chromatography
(a technique that separates a sample into its individual parts) and
tandem mass spectroscopy (which measures the mass-to-charge ratio of
ions). Results showed that one type of DINCH metabolite, OH-MINCH,
was detected in 98% of the urine samples. But the concentration levels
of the metabolite were low and 275 times less than the most prevalent
phthalate metabolite, monoethyl phthalate, suggesting that levels of human exposure to DINCH are smaller. But researchers weren't just looking at concentration levels of DINCH.

Another aspect of the study was to analyze DINCH exposure by race. Of
the 100 pregnant women, half were African American, while the others
were Caucasian.

Concentrations of OH-MINCH were 50% higher in African American women
compared to Caucasian women, which was consistent with a 2017 study
that looked at phthalate levels, led by Abby Wenzel, a NIST postdoctoral researcher at the time.

Researchers hypothesized the difference in concentration levels could be attributed to the type of personal care products that African American
women use compared with Caucasian women and that these products are also replacing phthalates with DINCH. But further follow-up studies are needed
to understand the reasons for this discrepancy, the researchers said.

The researchers did not find evidence that the DINCH metabolites
interfered with regulating the signaling of specific hormones required
for pregnancy.

Using a method called transactivation assay, they added the metabolites
to chemical receptors in test tubes for two types of hormones: estrogen,
which is involved in sexual reproduction, and progesterone, which is
involved in pregnancy. The researchers monitored whether the DINCH
metabolites acted in ways similar to the hormones or interfered with
the regulation of the hormones.

No effects were observed in this study, but, according to Kucklick,
that doesn't mean they aren't there.

This work may lay the foundation for future standard reference materials
that could benefit research by organizations such as the Centers for
Disease Control and Prevention, which is also studying these compounds, especially phthalates in urine. Another area of interest is how DINCH
works in the body. But more immediately, additional testing and analysis
needs to be conducted to make sure the use of DINCH does not have
long-term consequences.

"We're always trying to learn about the chemicals we don't know
about. It's good to understand what we're being exposed to and what some
of the downsides of what these chemicals might be," said Kucklick.


========================================================================== Story Source: Materials provided by National_Institute_of_Standards_and_Technology_(NIST).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Abby G. Wenzel, Jessica L. Reiner, Satomi Kohno, Bethany J. Wolf,
John W.

Brock, Lori Cruze, Roger B. Newman, John R. Kucklick. Biomonitoring
of emerging DINCH metabolites in pregnant women in charleston,
SC: 2011- 2014. Chemosphere, 2021; 262: 128369 DOI: 10.1016/
j.chemosphere.2020.128369 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200925134725.htm

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