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