What is Diethyl phthalate* and Why Does It Matter?

Diethyl phthalate (DEP) is a synthetic chemical used to make plastics more flexible and to help fragrances last longer. You'll find it in personal care products like shampoos, lotions, and perfumes, as well as in industrial coatings and some food packaging. It enters drinking water primarily through manufacturing discharge and the breakdown of plastic materials in the environment. Wastewater treatment plants don't always remove it completely, so trace amounts can pass through into tap water supplies.

DEP belongs to a larger family of chemicals called phthalates, which scientists have studied extensively for their potential to disrupt hormones. At low levels, the health risks aren't fully understood, but research suggests that phthalates can interfere with the body's endocrine system — the network of glands and hormones that controls development, metabolism, and reproduction. The Environmental Working Group (EWG) has flagged phthalates as a group of concern, particularly for pregnant women, infants, and young children whose developing systems are more vulnerable. Some animal studies have linked DEP exposure to reproductive and developmental effects, though the evidence in humans is still being studied.

Currently, the EPA has not established a maximum contaminant level (MCL) specifically for diethyl phthalate in drinking water, meaning there is no federal legal limit utilities must meet. The EWG, however, maintains health guidelines based on current science, and the good news is that none of the 10 water systems where DEP was detected exceeded those guidelines. The average detected level was 0.173 parts per billion (ppb), with the highest recorded level reaching 0.35 ppb. While those numbers are relatively low, the absence of a federal limit means utilities have no legal obligation to reduce DEP even if levels rise. That gap between regulation and current science is worth paying attention to.

Geographically, New Jersey accounts for the largest share of detections, with 5 of the 10 affected systems located there. Texas follows with 3 systems, while Virginia and Washington, D.C. each reported 1 detection. New Jersey's pattern makes sense given its dense concentration of chemical manufacturing and industrial facilities, particularly along the northeastern corridor. Urban and industrialized areas tend to see higher rates of phthalate contamination simply because more potential sources — factories, wastewater plants, and aging infrastructure — exist nearby. Texas detections likely reflect a mix of industrial activity and the sheer size of its water system network.

The most effective way to remove diethyl phthalate from your drinking water is through reverse osmosis (RO) filtration. A quality RO system can remove up to 99% of phthalates and hundreds of other contaminants by pushing water through a semi-permeable membrane that blocks chemical molecules. Activated carbon filters also reduce phthalate levels meaningfully, though they're generally less thorough than RO on their own. Echo Water's reverse osmosis systems are designed to address exactly this kind of low-level chemical contamination — the stuff that doesn't trigger regulatory alarms but still deserves attention. If you live in New Jersey, Texas, Virginia, or D.C., it's a smart idea to pull your local water quality report and see whether DEP shows up in your system's data. Even where levels are currently below health guidelines, filtering your water adds a reliable layer of protection that doesn't depend on regulatory updates or utility decisions. That kind of control is worth having.

Regulatory Standards for Diethyl phthalate*

Cities With the Highest Diethyl phthalate* Levels

States Most Affected by Diethyl phthalate*

Frequently Asked Questions

Related Contaminant Guides