A four-month study on the review of published literature pertaining to chemical emissions of styrene-based resin used in the cured-in-place pipe (CIPP) process, found that existing studies do not adequately capture worker exposures or levels in the surrounding areas to which workers or citizens may be exposed.
The study was commissioned by the National Association of Sewer Service Companies (NASSCO) after a 2017 report suggested CIPP workers may be at risk to chemical air emissions exposure. The literature review is the first element in NASSCO’s effort to obtain factual information about any risks to workers.
The study started last December and completed April 6, 2018, by researchers at the University of Texas at Arlington (UTA) Center for Underground Infrastructure Research and Education (CUIRE), and the Institute for Underground Infrastructure (IKT) in Germany. The team determined that spatial variation of concentrations, and variations in concentrations with different meteorological conditions, are not well-determined.
Most of the steam-cure studies captured temporal variation in emissions, by measuring concentrations before, during and after curing. The studies were less complete in capturing spatial variation in concentrations, measuring styrene around the termination manhole, or inside the manhole or sewer pipe itself.
Maximum values at the outlet point and inside the terminal manhole ranged from 20 to 1,070 ppm levels that exceed some exposure limits. However, since workers and certainly the public should not typically enter or stand directly at the termination manhole in the exhaust plume, this information is not very helpful.
At the steam-cured sites, additional field measurements of styrene concentrations surrounding the terminal manhole are needed. Only four of the steam-cure studies measured concentrations at least three feet away from the terminal manhole, versus in the manhole itself or in the exhaust plume.
On one project, employees walked the construction area periodically, but spent most of the time in their work trucks due to the cold weather. Hence, these measurements were likely not typical of worker exposures. Additional worker exposure data should be collected to capture variability in source emission rate, meteorological conditions, and the worker’s location with respect to the terminal manhole.
Atmospheric concentrations of compounds are functions of the source emission rate, meteorological conditions, and the receptor location. Since concentrations are expected to vary as a function of distance from the manhole, measuring at few locations gives an incomplete picture. In addition, concentrations are expected to vary with wind speed and direction, so one day’s measurements do not capture what levels may be under differing meteorological conditions.
These earlier studies also do not adequately capture variations in emission rates from different kinds (different diameters, lengths, etc.) of pipes. The overall results of the project at UTA/CUIRE/IKT indicated that the 21 papers reviewed have questionable methodologies, and therefore, the results presented are not conclusive. The researchers recommended additional sampling, and data evaluation and analysis, as a second phase of this study.
Dr. Mo Najafi, director of CUIRE, supervised this project. Dr. Melanie Sattler provided quality control in conducting the literature review, and prepared a plan for sampling and analysis of emissions. Sattler is the Syed Qasim Endowed Professor of Environmental Engineering at UTA, with a specialization in air quality.
Dr. Kevin Schug developed a plan for emissions analysis in Phase 2. Schug is the Shimadzu Distinguished Professor of Analytical Chemistry, and Founder and Director of the Collaborative Laboratories for Environmental Analysis and Remediation (CLEAR) at UTA.
IKT accessed German and European publications to augment the literature review for Phase 1. The Institute for Underground Infrastructure is a neutral, independent non-profit institute in Gelsenkirchen, Germany. Team members included Bert Bosseler, Thomas Brueggemann and Dieter Homann.
Graduate Research Assistants, Vinayak Kaushal, Gomathy Iyer, Satish Kakkera, Seyed Korky, Anushree Nayak, Sahar Habibzadeh and Reza Farazifard, at CUIRE, assisted in conducting the literature review.
NASSCO is now proceeding with the next part of the research. It is requesting proposals to evaluate the potential release of organic chemicals in the steam exhaust and other release points during pipe rehabilitation using CIPP.