Cured-in-Place Pipe: The Role of Engineers in Worker and Public Safety

September/October 2017

Cured-in-Place Pipe: The Role of Engineers in Worker and Public Safety


ANDREW J. WHELTON“Engineers, in the fulfillment of their professional duties, shall hold paramount the safety, health, and welfare of the public.” – NSPE Code of Ethics, Canon 1

Sewer, drinking water, and stormwater pipes are aging across the nation, and repairing them rapidly and at low cost is an urgent priority. For the past 30 years, engineers who work for municipalities and state transportation agencies have increasingly selected trenchless repair technologies to repair these pipes. Cured-in-place pipe, or CIPP, is one such technology and has become so popular that it’s being used to repair about 50% of all US water pipes. Instead of needing to excavate and replace a damaged water pipe, the innovative CIPP process allows a new plastic pipe to be chemically manufactured inside the existing damaged pipe. Steam- and hot water-cured CIPP technologies are the most common methods used.

Over the years, persons near CIPP installation sites have complained of odors and illness. Complaints have become so routine that CIPP contractors, engineers at consulting firms, and municipalities have issued website and Facebook postings, and released pamphlet and Twitter announcements, that have declared the exposures are “safe for people and animals,” “[styrene] will only be present at a few ppm,” and “don’t be alarmed.”

Styrene is one of many compounds used, but it is not used in all CIPP processes. Some homeowner associations and elected officials have propagated those messages into their communities.

But, in 2015, others discovered 1,070 ppm styrene was emitted from a downtown Los Angeles CIPP installation. For reference, 700 ppm is the “immediately dangerous to life and health” concentration that requires workers to wear respiratory protection. No respiratory protection was reportedly used during the Los Angeles study. Exposures that do not cause acute adverse health effects to the public have been estimated at less than 5 ppm, but even lower for children. In 2004, an engineering firm reported 110 ppm styrene was emitted at a Canadian CIPP sewer repair site. Despite these data, engineers trained on the use and oversight of the CIPP process are often not warned about these conditions.

In 2016, the National Science Foundation provided us rapid response funding to conduct air monitoring at CIPP stormwater pipe sites in California and sanitary sewer sites in Indiana. Results of our new study are explained in a news release at, are posted at, and in the journal Environmental Science & Technology Letters. Our testing revealed unreported worksite safety risks, and that previous assumptions about CIPP-induced chemical exposures were incorrect. For example, while steam was used to install the seven CIPPs we tested, the white material emitted into the air was not steam. We discovered the chemical plume was a multiphase mixture that included partially cured resin, particulates, droplets, organic vapors, and some water vapor. We also discovered numerous chemicals were released from CIPP sites, not just styrene. These other chemicals may have contributed to the detectable odor. No credible evidence indicates styrene is the sole cause of the detectable odor, as multiple chemicals can contribute to a single odor.

Most concerning was that the short- and long-term health effects associated with inhalation and dermal exposure to the multiphase mixture are unknown. Prior studies have attempted to collect only organic vapor—sometimes far away from the actual emission points. When the pulmonary toxicology experiments were conducted by exposing the mixture to mouse lung cells, cell death was detected for materials collected from two of the four sites. This suggests that there are CIPP operational conditions that may decrease the potential for hazardous health effects. Respiratory protection was not worn by workers, and the public walked through the chemical plumes.

While CIPP technology has been used since the 1980s, the implications of this new study cannot be understated. Based on available data, we argue that the following claims presently disseminated to the public are false: (1) styrene levels caused by CIPP are only “a few ppm,” (2) exposure to the chemicals emitted is “harmless,” (3) the white plume is “steam,” and (4) the odor is caused by styrene alone. Since exposures can be highly variable in chemical composition, concentration, and exposure duration, our findings demonstrate the need for further investigation.

CIPP technology likely can be used without endangering human health or the environment, but this will require engineers to hold paramount public health, safety, and welfare in the conduct of their duties. Stringent and enforced specification requirements should include proper personal protective equipment, setback distances, worksite air monitoring, capture and proper disposal of all emissions and waste, as well as the immediate reporting of complaints to health departments and fire departments.

To assist engineers in understanding and improving the safety, selection, and performance of plastics technologies, including CIPP, our team offers training.

Andrew J. Whelton ( is an assistant professor of civil, environmental, and ecological engineering at Purdue University. Additional contributors are Purdue professor Chad Jafvert (civil, environmental, and ecological engineering), assistant professor Brandon Boor (civil engineering), assistant professor John Howarter (materials, environmental, and ecological engineering), professor Jeffrey Youngblood (materials engineering), and assistant professor Jonathan Shannahan (health sciences).

This research was funded by National Science Foundation award 1624183, Purdue University, and public donations. Learn more at