Underground Construction - July 2021 - 38

PART 1
This is the first in a series of articles by NASSCO's Technical
Advisory Council (TAC) discussing the health and safety aspects
of styrene in cured-in-place pipe (CIPP) method renewal.
UNDERSTANDING STYRENE AND CIPP
By NASSCO Technical Advisory Council Chair Christopher Garrett, P.E.,
Brown and Caldwell
The topic of styrene safety has garnered a lot of attention in
recent years. For more than a decade the effects of styrene
cure water and condensate have been documented on
receiving waters. Since 2017 academic research and customer
concerns about CIPP acute and chronic health concerns has
brought this issue to the forefront for suppliers, contractors,
engineers, and owners. As the CIPP industry looks forward
to the next 50 years of providing effective rehabilitation of
our aging infrastructure, a better understanding of styrene
emissions is an idea whose time has come. NASSCO is
committed providing sensible best practices that promote
worker safety while funding research to evaluate the challenge
and establish a scientific basis for future recommendations.
Styrene is the ideal monomer used for cross-linking polyester
and vinyl ester resins. Due to its history of success, styrene
is preferred over alternative monomers for CIPP. With a low
threshold for human detection, styrene odor from CIPP
installations has documented complaints from utility customers
who are concerned about protections and exposure concerns
with CIPP.
To date, styrene-based resins are not used in CIPP
rehabilitation of drinking water assets, and potential odors
from sanitary sewer installations can be significantly reduced
by filling household plumbing traps with water. Also, styrene
emissions from CIPP are not regulated. Industry advocates
and regulatory agencies have published widely varying
exposure thresholds, including the United States Environmental
Protection Agency (EPA), the National Institute for Occupational
Safety and Health (NIOSH), the Occupational Safety and
Health Administration (OSHA), and the American Conference
of Governmental Industrial Hygienists (ACGIH). Amongst these
varying exposure limit thresholds, limiting human exposure to
less than 20 parts per million (ppm) is a conservative basis that
could be a standard for establishing work site best practices.
Styrene Facts
Regarding CIPP
* Styrene is a monomer that is
an important component of
the CIPP thermoset resins for
the past 50 years
* Polyester and Vinyl Ester
resins contain approximately
23% to 40% styrene
* Styrene is generally noticeable
at levels less than 1 ppm
* There is no regulatory
standard for styrene emission.
Different thresholds for
exposures are published -
EPA has a guideline for human
emission exposure at 20 ppm
for any duration
* NASSCO's " Guidelines for
the Safe Use and Handling
of Styrene-Based Resins
in CIPP " recommends a
15-foot perimeter around
emissions and exhaust
stacks a minimum of 6 feet
above ground as mitigative
measures to ensure low
styrene exposure.
38 JULY 2021 | UCONonline.com
http://www.UCONonline.com
Underground Construction - July 2021

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