Appendix D Food Codes for NHANES - OEHHA

Scientific Review PanelSRP Draft Version 2 February,June 2012
OEHHA believes that a Random-effects model is appropriate because OEHHA
assumes that the compounds found in exposure studies are a subgroup from a
population of congeners in each subgroup (i.e., dioxins and dioxin-like
compounds). Random-effects models assume there are multiple central
estimates and incorporate a between-compound estimate of error as well as a
within-compound estimate of error in the model. In contrast, a Fixed-effects
model assumes that observations scatter about one central estimate (Kleinbaum,
1988).
J.2.4 Carryover Rate
Looking at mother’s milk Tcos in terms of carryover rate suggests that
accumulation of dioxins and dioxin-like compounds in the mother’s body occurs
but varies by more than 100-fold among individual compounds (based on Tcos
derived from equation J-6).
Carryover rate, a term commonly used in the dairy literature (McLachlan et al.,
1990) is defined as the daily output of dioxins and dioxin-like compounds in
mother’s milk (µg/day) over the daily intake of dioxins and dioxin-like compounds
(µg/day). This rate is estimated by multiplying a dioxin’s and dioxin-like Tco by
the daily output of mother’s milk. Since milk production in human mothers are
about 1.0 kg/day, a dioxins and dioxin-like Tco is the carryover rate for a typical
60 kg woman.
A carryover rate > 1 would suggest that dioxins and dioxin-like compounds could
accumulate in body fat and transfer to the fat in mother’s milk. With an average
dioxin Tco of 3.7 d/kg, 370% of the mother’s average daily intake from ingested
sources, transfers to mother’s milk. This high transfer-value suggests that
accumulation or concentrating of carcinogenic dioxins and dioxin-like compounds
occur in the mother’s body. Oral Tcos less than one d/kg (e.g., 1,2,3,4,7,8-
HxCDF and 2,3,4,6,7,8-HxCDF) suggest that net metabolism or excretion occurs
in the mother’s body.
J.3 Mothers’ Milk Transfer Coefficients for PAHs
The polycyclic aromatic hydrocarbons (PAHs), a family of hundreds of different
chemicals, are characterized by fused multiple ring structures. These compounds
are formed during incomplete combustion of organic substances (e.g. coal, oil
and gas, garbage, tobacco or charbroiled meat). Thus, PAHs are ubiquitous in
the environment and humans are likely to be exposed to these compounds on a
daily basis. PAHs are a common pollutant emitted from Hot Spots facilities and
are evaluated under the program.
Only a small number of the PAHs have undergone toxicological testing for cancer
and/or noncancer health effects. PAHs with cancer potency factors are the only
ones that can be evaluated for cancer risk using risk assessment. However,
PAHs that lack cancer potency factors have been measured in various studies
J-18