Table 5.
Animals 5–20 μg/dL. Summary of key studies in rodents outlining neurodevelopmental and cognitive outcomes of blood lead levels between 5–20 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), Strain, Species, & Sex | Exposure Protocol | Age of Testing | Reference |
|---|---|---|---|---|---|
| 5–20 μg/dL, Animals - Rodents | |||||
| I. Exploratory Activity | |||||
| Unbaited Nose Poke Task | Decreased explorator y activity | 0.2–15 μg/dL | 0 ppm n=19 | PND 28 | Flores-Montoya & Sobin, 2015 |
| C57BL/6J Mice | (8 Males; 11 Females) | ||||
| Males & Females | |||||
| 30 ppm n=26 (16 Males; 10 Females) | |||||
| 230 ppm n=16 (12 Males; 4 Females) | |||||
| via lactation & drinking water PND 0–28 (offspring tested) | |||||
| Regression analysis | |||||
| Open Field, Number of Quadrant Crosses | NS | ||||
| Rotarod | NS | ||||
| Total Exploration Time During Novel Odor Recognition Task for males, but not females | NS | 0.02–20.31 μg/dL C57BL/6J Mice Males & Females |
0 ppm n=10 (8 Males; 2 Females) | Flores-Montoya et al., 2015 | |
| 30 ppm n=10 (5 Males; 5 Females) | |||||
| 330 ppm n=13 (7 Males; 6 Females) | |||||
| via lactation & drinking water PND 0–28 (offspring tested) | |||||
| Regression analysis | |||||
| Open Field, Activity Counts | Decreased activity | <10 μg/dL, P | 0 ppm & 27 ppm | 1 yr | Leasure et al., 2008 |
| C57BL/6 Mice | (n= 6–8 Males; 6–8 Females, per group) | ||||
| Males | |||||
| via lactation & drinking water; Dam’s lead exposure: 14 days prenatal-PND 10 (offspring tested) | |||||
| Open Field, Activity Counts | NS | <10 μg/dL, P | |||
| C57BL/6J Mice | |||||
| Females | |||||
| II. Global Locomotor | |||||
| Amphetamine -Induced Motor Activity | Increased drug-induced locomotor activity | <10 μg/dL, P | 0 ppm & 27 ppm (n=6–9 Males; 6–9 | 1 yr | Leasure et al., 2008 |
| C57BL/6J Mice | Females, per group) | ||||
| Males | via lactation and drinking water; Dam’s lead exposure: 14 days prenatal- PND 10 (offspring tested) | ||||
| Amphetamine -Induced Motor | NS | <10 μg/dL, P | |||
| Activity | C57BL/6J Mice | ||||
| Female | |||||
| Running Wheel Activity | NS | <10 μg/dL, P | n=6 (Male) | ||
| C57BL/6J Mice | |||||
| Male | |||||
| III. Motor Coordination | |||||
| Rotarod | Deficits | <10 μg/dL, P C57BL/6J Mice Male |
|||
| Rotarod | NS | <10 μg/dL, P C57BL/6J Mice Female |
|||
| IV. Odor Recognition | |||||
| Novel Odor Recognition Task | Preference for familiar over novel odor | 0.02–20.31 μg/Dl C57BL/6J Mice |
0 ppm n=10 (8 Males; 2 Females) | PND 28 | Flores-Montoya et al., 2015 |
| Male | |||||
| 30 ppm n=10 (5 Males; 5 Females) | |||||
| & 330 ppm n=13 (7 Males; 6 Females) | |||||
| via lactation & drinking water | |||||
| PND 0–28 (offspring tested) | |||||
| Novel Odor Recognition Task | NS | 0.02–20.31 μg/dL | |||
| C57BL/6J Mice | |||||
| Female | |||||
| V. Cognitive Flexibility | |||||
| Delayed Spatial Alternation | Deficits | 19 μg/dl, SS Long-Evans Rats |
0 ppm & 15 ppm n=15 per group (Male) | 22 weeks | Alber & Strupp, 1996 |
| Male | via drinking water PND 25- through testing | ||||
| Cued Alternation | NS | ||||
| Spatial Alternation | NS | ||||
| VI. Delay of Reinforcement/Impulsivity | |||||
| Fixed-Ratio Waiting-for-Reward Schedule of Reinforcement (FR50) | Deficits | 10.8 μg/dL, SS Long-Evans Rats Male |
0 ppm & 50 ppm n=12 per group (Male) |
PND 60 | Brockel & Cory-Slechta, 1998 |
| via drinking water PND 21 through testing | |||||
| Fixed Interval Schedule-Controlled (FI 1 Minute) | NS | 11.4 μg/dL, SS Long-Evans Rats Male |
0 ppm & 50 ppm n=10 per group (Male) |
PND 21 through testing | Cory-Slechta & Brockel, 2002 |
| via drinking water PND 21 through testing | |||||
| Fixed Interval Schedule-Controlled (FI 1 Minute) | NS | 7.2 μg/dL, SS Long-Evans Rats Male |
0 ppm n=13 50 ppm n=14 |
PND 21 through testing | Cory-Slechta, O'Mara, Brockel, 1998 |
| (Male) | |||||
| via drinking water PND 21 through testing | |||||
| Fixed Interval Schedule-Controlled (FI 1 Minute) | NS | 15.9 μg/dL, Fischer-344 Rats Male |
0 ppm & 50 ppm n=16 per group (Male) via drinking water from arrival through testing |
16 mos old at arrival. Testing began after 6th mos of exposure through testing | Cory-Slechta & Pokora, 1991 |
| Fixed Interval Schedule-Controlled (FI 1 Minute) | NS | PND 21: 11.3 μg/dL | 2 mg/kg/day in 5 mis | PND 21, 8 mos. 16 mos | |
| Deficits | PND 8 months: 17.1 μg/dL | PND 21:n=30 PND 8mos:n=34 PND 16mos:n=42 |
at arrival. | ||
| NS | PND 16 months: 18.3μg/dL Fischer-344 Rats Male |
(Male) Via drinking tube from arrival through testing |
Testing began after 2.5 mos of lead exposure | ||
| Variable Interval Schedule-Controlled | NS | PND 21: 11.3 μg/dL | |||
| (Fl Minute) | NS | PND 8 months: 17.1 μg/dL | |||
| NS | PND 16 months: 18.3μg/dL Fischer- 344 Rats Male |
||||
| Fixed Interval Schedule-Controlled (FI 1 Minute) | Deficits | 15–20 μg/dL Long-Evans Rats |
0 ppm & 25 ppm n=12 per group (Male) |
PND 50 | Cory-Slechta et al., 1985 |
| Male | via drinking water PND 21 through testing |
||||
| Fixed Interval Schedule-Controlled (FI 1 Minute) | Deficits | <20 μg/dL Long-Evans Rats Male |
0 ppm & 50 ppm n=6 per group (Male) via drinking water PND 21-PND 178 or PND 20-PND 335 |
PND 55 | Cory-Slechta et al., 1983 |
| Fixed Interval Schedule-Controlled (FI 1 Minute) | Deficits | <10 μg/dL Sprague-Dawley Rats |
0 ppm n=8 50 ppm n=ll |
PND 55 | Cory-Slechta et al., 1979 |
| Male | |||||
| (Male) | |||||
| via drinking water from PND 21 through testing | |||||
Abbreviations: MOS=Months; NS=Not Significant; P=Peak; PND=Postnatal Day; PPM=Parts Per Million; SS=Steady State; YR=Year