Abstracts (PDF file, 1.8MB) - Society for Risk Analysis

SRA 2013 Annual Meeting Abstracts
T2-K.3 Holman, E*; Francis, R; Gray, G; U.S. Environmental
Protection Agency (author 1), George Washington University
(authors 1-3); eholman@gwmail.gwu.edu
Comparing Science Policy Choices in Chemical Risk
Assessments Across Organizations
Environmental and public health organizations including the
World Health Organization (WHO) and the U.S. Environmental
Protection Agency (USEPA) develop human health risk values
(HHRV) that set ‘safe’ levels of exposure to non-carcinogens.
This analysis evaluates specific science policy choices made in
the context of setting HHRV and differences in these decisions
observed across organizations. These choices include the
selection of principal study, critical effect, the point of
departure (POD) approach and numerical estimate, and the use
of uncertainty factors (UF). By systematically evaluating each
choice while recognizing connections among choices, the goal
is to elucidate the most common sources of agreement and
disagreement across organizations. In setting the UF,
organizations typically use default 10X values, reduced values
(often 3X), or chemical-specific adjustment factors. A common
reason for using a reduced UF with a LOAEL POD is that the
observed critical effect is considered minimally adverse. If
chronic studies indicate that subchronic POD are more
sensitive, a full 10X UF may not be required for a subchronic
principal study. While older assessments often use default
values, the use of PBPK modeling and human study data is
becoming increasingly common, resulting in reduced UFs to
account for interspecies and intraspecies extrapolations. To
account for database deficiencies, organizations may invoke a
database UF for concerns such as the lack of a specific study
type or potential carcinogenicity. This analysis also examines
cases where given the same or similar toxicological data, one or
more organizations set an HHRV but other organizations do
not. Included in the analysis are HHRV from the following
organizations: USEPA, WHO, Health Canada, RIVM
(Netherlands), and the U.S. Agency for Toxic Substances and
Disease Registry. (The opinions are those of the authors and do
not necessarily reflect policies of USEPA or the U.S.
government.)
P.126 Holser, RA; Russell Research Center;
Ronald.Holser@ars.usda.gov
Microbial contamination in poultry chillers estimated by
Monte Carlo simulations
The risk of contamination exists in meat processing facilities
where bacteria that are normally associated with the animal are
transferred to the product. If the product is not stored, handled,
or cooked properly the results range from mild food poisoning
to potential life threatening health conditions. One strategy to
manage risk during production is the practice of Hazard
Analysis and Critical Control Points (HACCP). In keeping with
the principles of HACCP a key processing step to control
bacterial growth occurs at the chiller. The risk of microbial
contamination during poultry processing is influenced by the
operating characteristics of the chiller. The performance of air
chillers and immersion chillers were compared in terms of
pre-chill and post-chill contamination using Monte Carlo
simulations. Three parameters were used to model the
cross-contamination that occurs during chiller operation. The
model used one parameter to estimate the likelihood of contact
and a second parameter to estimate the likelihood of
contamination resulting from that contact. A third parameter
was included to represent the influence of antimicrobial
treatments to reduce bacterial populations. Results were
calculated for 30%, 50%, and 80% levels of contamination in
pre-chill carcasses. Air chilling showed increased risk of
contamination in post-chill carcasses. Immersion chilling with
50 mg/L chlorine or 5% trisodium phosphate added to the
chiller water as antimicrobial treatments reduced
contamination to negligible levels in post-chill carcasses.
Simulations of combination air/immersion chiller systems
showed reductions of microbial contamination but not to the
extent of immersion chillers. This is attributed to the reduced
exposure time to antimicrobial treatments. These results show
the relation between chiller operation and the potential to
mitigate risk of microbial contamination during poultry
processing.
T2-B.1 Honeycutt, ME*; Haney, JT; State Government;
michael.honeycutt@tceq.texas.gov
IRIS improvements: meeting the needs of Texas
With a large land area, population, and concentration of
industry, Texas has a need for scientifically-defensible and
meaningful Toxicity Values (TV; e.g. RfD, RfC, Cancer Slope
Factors) to prioritize scarce resources. Relying on conservative
defaults in response to ever-present uncertainty as opposed to
data can result in assessments yielding safe values less than
background in certain media. While EPA states that IRIS
chemical assessments are not risk assessments, the risk
assessment implications of an IRIS TV are far reaching (e.g.,
implying background arsenic soil, fish, rice, and groundwater
levels exceed acceptable risk levels). Toxicologically-predictive
TVs are important to properly prioritize the 3,700+ remediation
sites in Texas so that agency actions and limited funds can be
focused on the sites which realistically pose the greatest public
health threat and thereby achieve the greatest real health risk
reduction. If a great multitude of sites exceed target risk or
hazard limits due to overly conservative TVs, then it is difficult
to properly prioritize sites for action to achieve the greatest
public health benefit. EPA has flexibility for post-Baseline Risk
Assessment risk management decisions when calculated media
risk-/hazard-based comparison values are exceeded at a site
where TCEQ does not. For the Texas Risk Reduction Program
(TRRP) rule, individual-chemical and cumulative risk and
hazard limits which trigger action have been included in the
rule a priori, which while straight forward does not offer risk
management flexibility. For example, the individual-chemical
excess risk limit which triggers action for a chemical in surface
soil is 1E-05. This often triggers action under TRRP when EPA
would often have the flexibility at an individual-chemical risk