Chemical Alternative to Phthalates Looks Promising

You never know what health-related problems may reveal themselves in the future, but so far a chemical alternative to phthalates looks promising–especially in terms of the chemical appearing to not be a hormone-disruptor. Researchers analyzed urine samples from pregnant women to look for the presence of the phthalate-alternative called DINCH for short [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 key reproductive hormones, progesterone and estrogen. 

Backstory

Detergents, shampoos, vaginal douches, soaps, food packaging and a host of other everyday items including household products and clothing 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.

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, medical tubing and food packaging.

However, in addition to other adverse health problems, 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. Nonetheless, DINCH has been used since 2002 in the U.S. and can be found in commercial products such as toys, medical devices and food packaging. Now researchers are studying the effects of this chemical on human health, especially its ability to alter the endocrine (hormonal) system.

Study overview

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.

At the Hollings Marine Laboratory 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.

The Race Factor: 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 by race.  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. Further follow-up studies are needed to understand the reasons for this discrepancy.

No Endocrine-Disrupting Activity Observed:  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.

What’s next

Just because there were no observable effects of the DINCH chemical on reproductive hormones in the study does not mean there are none.  Much more testing and analysis needs to be conducted to make sure the use of DINCH does not have long-term consequences on human health and well-being.

 


Journal Reference:  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