Small rises in blood pressure were linked to the chemicals supposed to replace those previously found to be unsafe.
The phthalate compounds in question - di-isononyl phthalate (DINP) and di-isodecyl phthalate (DIDP) - are replacements for another chemical, di-2-ethylhexylphlatate (DEHP), which the same researchers proved in previous research to have similar adverse effects.
The phthalates are meant to strengthen plastic wraps and processed food containers, among other household items.
The two new pieces of research are published in the journals Hypertension and The Journal of Clinical Endocrinology and Metabolism.
In the Hypertension study, for every 10-fold increase in the amount of phthalates consumed, there was a 1.1 millimeters of mercury (mmHg) increase in blood pressure.
In the other study, one in three adolescents with the highest DINP levels had the highest insulin resistance, while for those with the lowest concentrations of the chemicals, only 1 in 4 had insulin resistance.
Growing concerns over environmental chemicals and insulin resistance
Study leader Dr. Leonardo Trasande, a professor at NYU Langone, says:
"Our research adds to growing concerns that environmental chemicals might be independent contributors to insulin resistance, elevated blood pressure and other metabolic disorders."
Prof. Trasande would like the 1976 Toxic Substances Control Act updated: "Our study adds further concern for the need to test chemicals for toxicity prior to their broad and widespread use, which is not required under current federal law."
Other research from Prof. Trasande in 2013 confirmed a link between DEHP exposure and hypertension in Americans. DEHP was used as a plasticizer but banned in Europe in 2004 - DINP and DIDP are designed to replace it. Perhaps the safer alternatives lie in not using plastics at all.
"Alternatives to DIDP and DINP include wax paper and aluminum wrap; indeed, a dietary intervention that introduced fresh foods that were not canned or packaged in plastic reduced phthalate metabolites substantially."
Prof. Trasande adds that there are "safe and simple" steps that can limit exposure to phthalates, including:
- Do not microwave food in plastic containers or covered by plastic wrap
- Do not wash plastic food containers in the dishwasher, where plasticizers can leak out
- Avoid phthalates by avoiding plastic containers labeled with the numbers 3, 6 or 7 inside the recycle symbol.
The results of the research come from blood and urine sample analysis of participants in the National Health and Nutrition Examination Survey (NHANES).
Since 1999, NHANES has surveyed 5,000 volunteers annually about risk factors and diseases. As part of the NYU Langone investigation, blood and urine samples were analyzed from a diverse group of children and adolescents aged between 6 and 19 years.
Blood and urine samples were collected once between 2008 and 2012, and the study volunteers' blood pressure was similarly measured. Diet, physical activity, gender, race/ethnicity, income, and other factors independently associated with insulin resistance and hypertension were also factored into the researchers' analysis.