Appendix D Food Codes for NHANES - OEHHA

Scientific Review PanelSRP Draft Version 2 February,June 2012
J.4.4 Population Transfer Coefficient (Tco) for Lead
OEHHA has derived transfer coefficients for lead using Equation J-9
Tcohma=(Cma/Cblood + )x(Cblood + /Cblood)x(Cblood/(Cair x BR))xFc1 xFc2 Eq. J-9
where:
Cma = geometric mean human milk lead level (µg/L-milk as wet weight)
Cblood + = geometric mean blood lead level during lactation (µg/dL)
Cblood = geometric mean blood lead level during non-lactating state (µg/dL)
Cair = geometric mean concentration of lead in ambient air (µg/m 3 )
BR = geometric mean breathing rate for adult women (14 m 3 /day)
Fc1 = conversion factor (L-milk)/(kg-milk) ~ (0.97)
Fc2 = conversion factor (dL)/(L) = 10
Cma is the geometric mean human milk lead level that incorporates all
(aggregated) air-related pathways of lead. Cblood + is the geometric mean blood
lead level among lactating women measured during lactation (µg/L). Cblood is the
geometric mean blood lead level taken from the general population during a nonlactating
state (µg/L). Cair is the geometric mean concentration of lead in the
ambient air (µg/m 3 ) inhaled by the same population where blood lead levels were
measured. BR is the geometric mean breathing rate for adult women (14 m 3 /day)
(see Chapter 2). Fc1 is the inverse of the specific gravity of breast milk (1.03
g/ml)(Sergen, 2006). Fc2 is the conversion from deciliters to liters.
J.4.4.1 Biotransfer from Blood to Milk
Three groups measured maternal blood lead before and during lactation along
with lead in mother’s milk (Gulson et al., 1997; Gulson et al., 1998a; Gulson et
al., 1998b; Sowers et al., 2002; Ettinger et al., 2004). However, Sowers et al.
reported unusually high levels of lead in breast milk relative to blood, which
suggest contamination problems. It is possible that breast milk samples were
contaminated by the sampling collection technique (e.g. lead in the nipple
shields). However, it is also possible that a more efficient active transport
mechanism at lower blood lead levels could explain higher levels of lead in
breast milk relative to blood. More studies of mothers with low blood lead levels
are needed to further verify the results reported by Sowers et al.
For our purposes, Gulson et al (1995, 1997, 1998a, 1998b) and Ettinger et al
(2004) provide the best estimates of the change in blood lead levels before the
onset of lactation, during lactation and relative to the levels of lead in breast milk
(Gulson et al., 1997; Gulson et al., 1998a; Gulson et al., 1998b; Ettinger et al.,
2004).
J-44