Table 6.

Cynomolgus Monkeys. Summary of key studies in monkeys outlining neurodevelopmental and cognitive outcomes of blood lead levels below 20 μg/dL reported at p< .05. Excludes studies where peak levels were above 20 μg/dL. Excludes studies not explicitly reporting blood lead levels. Blood lead levels are presented as averages, unless otherwise noted, and appear as reported in respective studies. Inclusion/exclusion criteria were established to determine study selection.¹

Test	Outcome (Using adjusted scores when available)	Mean Blood Lead Level μg/dL)	Exposure Protocol	Age of Testing	Reference
<20 μg/dL, Cynomolgous Monkeys
I. Attention/Impulsivity/Discrimination Task
Discrimination Task Spatial Discrimination; No Irrelevant Cues	NS	15.4 μg/dL, SS 10.9 μg/dL, P Controls: 3 μg/dL (Note: Controls had BLLs between 2.9 & 3.5 μg/dL perhaps masking an effect at the low level of lead tested)	0 μg/kg/day (n=3 Males; n=3 Females) 50 μg/kg/day (4=Males; 4=Females) Experimenter administered PND 0 through testing	9–10 yrs	Gilbert & Rice, 1987
Irrelevant Form Cues	NS	15 μg/dL, P 11 μg/dL, SS	0 μg/kg/day (n=4 Males; n=3 Females) 50 μg/kg/day (n=4 Males; n=4 Females) Experimenter administered PND 0 through testing	3–4 yrs	Rice, 1985
Irrelevant Form & Color Cues	NS
Acquisition of Nonspatial Form Discrimination	NS
Acquisition of Nonspatial Color Discrimination with Irrelevant Form Cues	NS
Acquisition of Nonspatial Form Discrimination with Irrelevant Color Cues	NS
Spatial Form Discrimination	Deficits
Nonspatial Color Discrimination with Irrelevant Form Cues	Deficits
Nonspatial Form Discrimination with Irrelevant Color Cues	Deficits
Delayed Alternation	Deficits
II. Delay of Reinforcement
Differential Reinforcement of Low Rate (DRL varied between 5–30 sec)	NS	15.4 μg/dL, SS 10.9 μg/dL, P Controls: 3 μg/dL (Note: Controls had high levels of lead, perhaps masking an effect of the low level of lead tested)	0 μg/kg/day (n=4 Males; n=3 Females) 50 μg/kg/day (n=4 Males; n=4 Females) Experimenter administered PND 0 through testing	3 yrs	Rice & Gilbert, 1985
III. Memory
Acquisition of Alternation Tasks	NS	15.4 μg/dL, P 10.9 μg/dL, SS	0 μg/kg/day (n=4 Males; n=3 Females) 50 μg/kg/day (n=4 Males; n=4 Females) Experimenter administered PND 0 through testing	7–8 yrs	Rice & Karpinski, 1988
Acquisition of Delayed Alternation	Deficits

Abbreviations: =Blood Lead Level; NS=Not Significant; P=Peak; PND=Postnatal Day; SS=Steady State; YRS=Years