HEALTH CONSULTATION
Analysis of Risk Factors for Childhood Blood Lead Levels
El Paso, Texas, 1997-2002
EL PASO COUNTY METAL SURVEY
EL PASO, EL PASO COUNTY, TEXAS
Table 1. Percentage of Children With Elevated Blood Lead Levels by Data Set
| Data Set | N | Percentage Greater Than 10 µg/dL | ||
| Combined | Confirmed | Combined Results* | Confirmed Results+ | |
| Original CLPPP | 39,145 | 38,665 | 2.3 | 1.2 |
| CLPPP Geocoded | 38,725 | 38,258 | 2.2 | 1.2 |
| Soil Sampling Area | 3,436 | 3,345 | 5.2 | 2.9 |
| Soil Direct Match | 497 | 484 | 5.2 | 2.7 |
* Combined results include
nonelevated results, unconfirmed elevated results, and confirmed elevated results.
+ Confirmed results include nonelevated results and confirmed elevated
results.
Table 2. 1997-2002 CLPPP Data For El Paso,
Texas, For Children Aged 0 To 6 Years With A Valid Address Recorded Confirmed
Blood Lead Level For Children With Elevated Blood Lead Status
N=38,258
| Characteristic | N | Mean | std. dev. | Median | min. | max. |
| Age of child (years) | 38,258 | 2.8 | 1.93 | 2.2 | 0 | 6.99 |
| Age of child's housing (years) | 25,772 | 36.7 | 21.06 | 33 | 1 | 123 |
| Percentage of population in census tract who Immigrated from Mexico in 1990-2000 | 38,255 | 8.7 | 4.1 | 8.1 | 0 | 21.8 |
| Percentage of population in block group living below poverty level | 38,255 | 30.6 | 16.68 | 29.1 | 0 | 100 |
| Distance of residence from smelter (miles) | 38,258 | 9.9 | 5.28 | 9.8 | 0.6 | 31.6 |
| Blood lead level of child in micrograms/dL | 38,258 | 3.4 (Geometric mean for blood lead = 2.9) |
2.28 | 3 | 0 | 58 |
Table 3. 1997-2002 CLPPP for El Paso, Texas,
Children Aged 0 To 6 Years With A Valid Address Recorded Confirmed Blood Lead
Level For Children With Elevated Blood Lead Status
N=38,258
| Characteristic | Frequency | Percentage |
| Sex | ||
| Female | 18,729 | 49.0 |
| Male | 19,476 | 51.0 |
| (information not available) | 53 | |
| Age | ||
| Less than 1 year | 6,954 | 18.2 |
| 1 year | 9,901 | 25.9 |
| 2 years | 5,536 | 14.5 |
| 3 years | 4,272 | 11.2 |
| 4 years | 4,529 | 11.8 |
| 5 years | 3,657 | 9.6 |
| 6 years | 3,409 | 8.9 |
| On Medicaid at Time of Test | ||
| No | 822 | 2.2 |
| Yes | 37,436 | 97.9 |
| Blood Lead Level | ||
| Less than 10 micrograms/dL | 37,795 | 98.8 |
| 10 to 20 micrograms/dL | 410 | 1.1 |
| 20 to 30 micrograms/dL | 38 | 0.1 |
| Greater than 30 micrograms/dL | 15 | 0.04 |
| Elevated Blood Lead | ||
| Yes | 463 | 1.2 |
| No | 37,795 | 98.8 |
Table 4. 1997-2002 CLPPP for El Paso, Texas
Children Aged 0 to 6 Years With a Valid Address Recorded Confirmed Blood Lead
Level For Children With Elevated Test Results
N=38,258
| Characteristic | N | % Elevated* |
| Age of child in years | ||
| <1 | 6,954 | 0.4 |
| 1 | 9,901 | 1.2 |
| 2 | 5,536 | 1.7 |
| 3 | 4,272 | 1.9 |
| 4 | 4,529 | 1.4 |
| 5 | 3,657 | 1.1 |
| 6 | 3,409 | 1 |
| Sex of child | ||
| Male | 19,476 | 1.3 |
| Female | 18,729 | 1.1 |
| Housing age (years) | ||
| <10 | 2,319 | 0.5 |
| 10 to 20 | 3,265 | 0.8 |
| 20 to 30 | 5,202 | 0.7 |
| 30 to 40 | 3,835 | 0.9 |
| 40 to 50 | 5,000 | 1.4 |
| 50 to 60 | 3,024 | 1.4 |
| >60 | 3,127 | 3.5 |
| Percentage census tract population immigrated from Mexico during 1990-2000 | ||
| 0 to 5% | 7,167 | 0.7 |
| 5 to 10% | 18,601 | 1 |
| 10 to 15% | 10,121 | 1.4 |
| 15 to 20% | 1,588 | 3.6 |
| >20% | 778 | 3.5 |
| Percentage living below poverty level in block group | ||
| <20% | 11,064 | 0.7 |
| 20 to 40% | 18,673 | 1.2 |
| 40 to 60% | 5,916 | 1.8 |
| 60 to 80% | 2,468 | 2.2 |
| >80% | 134 | 4.5 |
| Lives in area with soil testing | ||
| No | 34,913 | 1.1 |
| Yes | 3,345 | 2.9 |
| Distance from smelter | ||
| <1 mile | 24 | 29.2 |
| 1 to 2 miles | 896 | 2.6 |
| 2 to 3 miles | 2,289 | 2.6 |
| 3 to 4 miles | 2,639 | 2.3 |
| 4 to 5 miles | 2,595 | 2.1 |
| 5 to 6 miles | 2,770 | 1.5 |
| 6 to 7 miles | 2,036 | 1 |
| 7 to 8 miles | 2,037 | 0.8 |
| 8 to 9 miles | 1,841 | 1 |
| >9 miles | 21,131 | 0.8 |
| Distance from smelter | ||
| <1.5 miles | 322 | 2.8 |
| 1.5 to 3 miles | 2,887 | 2.8 |
| 3 to 4.5 miles | 3,981 | 2.3 |
| 4.5 to 6 miles | 4,023 | 1.6 |
| 6 to 7.5 miles | 2,624 | 1 |
| 7.5 to 9 miles | 3,290 | 0.9 |
| 9 to 10.5 miles | 3,845 | 1 |
| 10.5 to 12 miles | 4,644 | 0.8 |
| >12 miles | 12,642 | 0.7 |
* missing values not included in calculations/statistics
Table 5. Correlational Matrix of Potential
Predictor Variables and Natural Logarithm of Blood Lead Level for Greater El
Paso Data Set
N=38,258
| Correlations Variable | LNBLL | HOUSING | MEXIMMIG | POVERTY | KIDAGE | KIDAGE2 | SMELTDST |
| LNBLL | 1.0000 | 0.1762 | 0.1569 | 0.1641 | 0.0676 | 0.0249 | -0.1714 |
| HOUSING | 0.1762 | 1.0000 | 0.3745 | 0.4031 | 0.0124 | 0.0146 | -0.6755 |
| MEXIMMIG | 0.1569 | 0.3745 | 1.0000 | 0.5726 | 0.0045 | 0.0028 | -0.4690 |
| POVERTY | 0.1641 | 0.4031 | 0.5726 | 1.0000 | 0.0115 | 0.0065 | -0.4312 |
| KIDAGE | 0.0676 | 0.0124 | 0.0045 | 0.0115 | 1.0000 | 0.9720 | -0.0098 |
| KIDAGE2 | 0.0249 | 0.0146 | 0.0028 | 0.0065 | 0.9720 | 1.0000 | -0.0105 |
| SMELTDST | -0.1714 | -0.6755 | -0.4690 | -0.4312 | -0.0098 | -0.0105 | 1.0000 |
Note:
LNBLL = natural logarithm of blood lead level.
HOUSING = age of housing.
MEXIMMIG = percentage of population in 2000 census tract immigrating from Mexico
in 1990 to 2000.
POVERTY = percentage of population in 2000 block group living below poverty
level.
KIDAGE = child's age.
KIDAGE2 = child's age squared.
SMELTDIST = distance from smelter.
Range of possible R-values is -1 to 1.
Table 6. Multiple Logistic Regression Results
for N=25,149 Medicaid Children, Ages 0 to 6 Years, for 1997 to 2002 CLPPP Data
for El Paso, Texas
Model Outcome Is Confirmed Elevated Blood Lead Status (10 µg/dL) Controlling
for Child's Age
| Parameter | Coefficient Point Estimate | Standard Error | p-value | Change | Adjusted Odds Ratio | 95% Confidence Intervals | |
| lower | upper | ||||||
| Intercept | -4.6937 | 0.0728 | <.0001 | ||||
| Sex | 0.0651 | 0.0576 | 0.259 | male vs. female | 1.139 | 0.909 | 1.427 |
| Age of child's housing | 0.0119 | 0.00333 | 0.0004 | 20 years older | 1.269 | 1.113 | 1.446 |
| Percentage of population in block group living below poverty level | 0.00877 | 0.00408 | 0.032 | 20% increase | 1.192 | 1.016 | 1.398 |
| Percentage of population in census tract who Immigrated from Mexico in 1990-2000 | 0.0409 | 0.0167 | 0.015 | 5% increase | 1.227 | 1.042 | 1.445 |
| Distance from smelter (in miles) | -0.0628 | 0.023 | 0.006 | 1 mile more distant | 0.939 | 0.898 | 0.982 |
Interpretation of the Odds Ratio:
A 20-year increase in the age of child's housing was associated with a 27% increase in odds of child having an elevated blood lead level.
Table 7. 1997-2002 CLPPP data for El Paso,
Texas, for Children Ages 0 to 6 Years With Residences Matching EPA Soil-Sampled
Residences Confirmed Blood Lead Level for Elevateds
| Characteristic | N | Mean | std. dev. | Median | min | max |
| Age of child (years) | 484 | 3.0 | 2.02 | 2.6 | 0 | 6.99 |
| Age of child's housing (years) | 426 | 63.6 | 25.07 | 65.75 | 1 | 123 |
| Percentage of population in census tract who Immigrated from Mexico in 1990-2000 | 484 | 12.9 | 5.15 | 10.5 | 4.1 | 21.8 |
| Percentage of population in block group living below poverty level | 484 | 12.9 | 12.86 | 40.6 | 6.2 | 73 |
| Distance of residence from smelter (miles) | 484 | 1.9 | 0.46 | 1.8 | 1.1 | 4.5 |
| Blood lead level of child in micrograms/dL | 484 | 4.1 (Geometric mean of blood lead = 3.6) |
2.57 | 4 | 0 | 26 |
| Soil lead level at residence (ppm) | 484 | 350.7 | 304.74 | 310.0 | 6.00 | 2180 |
Table 8. 1997-2002 CLPPP Data for El Paso,
Texas, Children Ages 0 to 6 Years With Residences Matching EPA Soil-Sampled
Residences Confirmed Elevated Blood Lead Status (10 µg/dL)
N=484
| Characteristic | Frequency | Percent |
| Sex | ||
| Female | 242 | 50.21 |
| Male | 240 | 49.8 |
| Age | ||
| Less than 1 year old | 90 | 18.6 |
| 1 year old | 104 | 21.5 |
| 2 years old | 67 | 13.8 |
| 3 years old | 64 | 13.2 |
| 4 years old | 46 | 9.5 |
| 5 years old | 52 | 10.7 |
| 6 years old | 61 | 12.6 |
| On Medicaid at Time of Test | ||
| No | 58 | 12.0 |
| Yes | 426 | 88.0 |
| Blood Lead Level (micrograms/dL) | ||
| Less than 10 | 471 | 97.31 |
| 10 to 20 | 11 | 2.27 |
| 20 to 30 | 2 | 0.41 |
| >30 | 0 | 0.0 |
| Elevated Blood Lead | ||
| Yes | 13 | 2.7 |
| No | 471 | 97.3 |
| Soil Lead Level at Residence (ppm) | ||
| 0 to 200 | 161 | 33.3 |
| 200 to 400 | 152 | 31.4 |
| 400 to 600 | 99 | 20.5 |
| >600 | 72 | 14.9 |
| Soil Lead Level at Residence 500 ppm | ||
| Yes | 110.0 | 22.7 |
| No | 374.0 | 77.3 |
(missing data not shown/included in calculations)
Table 9. 1997-2002 CLPPP Data for El Paso,
Texas, Children Ages 0 to 6 Years With Residences Matching EPA Soil-Sampled
Residences Confirmed Elevated Blood Lead Status (10 µg/dL)
N=484
| Characteristic | N | % Elevated |
| Age of child in years | ||
| <1 | 90 | 0 |
| 1 | 104 | 1.9 |
| 2 | 67 | 6 |
| 3 | 64 | 4.7 |
| 4 | 46 | 2.2 |
| 5 | 52 | 1.9 |
| 6 | 61 | 3.3 |
| Sex of child | ||
| Male | 240 | 4.2 |
| Female | 242 | 1.2 |
| Housing age in years | ||
| <10 | 17 | 0 |
| 10 to 20 | 0 | 0 |
| 20 to 30 | 22 | 0 |
| 30 to 40 | 35 | 0 |
| 40 to 50 | 54 | 3.7 |
| 50 to 60 | 55 | 1.8 |
| >60 | 241 | 3.3 |
| Percentage of population Immigrating from Mexico during 1990-2000 for census tract | ||
| 0 to 10% | 112 | 0 |
| 10 to 20% | 236 | 4.2 |
| >20% | 136 | 2.2 |
| Percentage living below poverty level in block group | ||
| <20% | 74 | 2.7 |
| 20 to 40% | 154 | 3.9 |
| 40 to 80% | 256 | 1.9 |
| Total | Male | Female | ||||
| N | % Elevated | N | % Elevated | N | % Elevated | |
| Soil lead lead level at residence in parts per million | ||||||
| 0 to 200 | 161 | 1.2 | 74 | 1.3 | 86 | 1.2 |
| 200 to 400 | 152 | 2 | 74 | 4.1 | 77 | 0 |
| 400 to 600 | 99 | 2 | 54 | 1.9 | 45 | 2.2 |
| >600 | 72 | 8.3 | 38 | 13.2 | 34 | 2.9 |
| Soil at residence above 500 ppm | ||||||
| No | 374 | 1.9 | 181 | 2.8 | 191 | 1 |
| Yes | 110 | 5.5 | 59 | 8.5 | 51 | 2 |
(missing information not shown/included in calculations)
Table 10. Correlational Matrix of Soil-Lead
with Covariates and Natural Logarithm of Blood Lead Level for Soil-Matched Data
Set
N=484
| Correlations Variable | LNBLL | HOUSING | MEXIMMIG | POVERTY | KIDAGE | KIDAGE2 | SOIL5 |
| LNBLL | 1.0000 | 0.1569 | 0.1753 | 0.1034 | 0.0742 | 0.0478 | 0.1353 |
| HOUSING | 0.1569 | 1.0000 | 0.3191 | 0.3269 | 0.0991 | 0.0976 | 0.5153 |
| MEXIMMIG | 0.1753 | 0.3191 | 1.0000 | 0.6846 | -0.0177 | -0.0242 | 0.0879 |
| POVERTY | 0.1034 | 0.3269 | 0.6846 | 1.0000 | 0.0123 | 0.0077 | 0.1388 |
| KIDAGE | 0.0742 | 0.0991 | -0.0177 | 0.0123 | 1.0000 | 0.9746 | 0.0269 |
| KIDAGE2 | 0.0478 | 0.0976 | -0.0242 | 0.0077 | 0.9746 | 1.0000 | 0.0237 |
| SOIL5 | 0.1353 | 0.5153 | 0.0879 | 0.1388 | 0.0269 | 0.0237 | 1.0000 |
Note:
LNBLL = natural logarithm of blood lead level.
HOUSING = age of housing.
MEXIMMIG = percentage of population in 2000 census tract immigrating from Mexico
in 1990 to 2000.
POVERTY = percentage of population in 2000 block-group living below poverty
level.
KIDAGE = child's age.
KIDAGE2 = child's age squared.
SOIL5 = soil lead level.
Range of possible R-values is -1 to 1.
Table 11. Simple Logistic Regression Results
for Medicaid Children, Ages 0 to 6 Years, for 1997 to 2002 CLPPP Data for El
Paso, Texas, Matched to 2003 EPA Data on Soil Sampling Model Outcome Is Confirmed
Elevated Blood Lead Status (10 µg/dL) Unadjusted result for each parameter
N = 426
| Parameter | N | Coefficient Point Estimate | Standard Error | p-value | Change | Unadjusted Odds Ratios | 95% Confidence Intervals | |
| lower | upper | |||||||
| Housing age | 376 | 0.3964 | 0.310 | 0.20 | 20 years older | 1.49 | 0.808 | 2.734 |
| % Poverty | 426 | 0.2297 | 0.527 | 0.66 | 20 % increase | 1.26 | 0.448 | 3.533 |
| % Mexican immigration | 426 | 0.0580 | 0.300 | 0.85 | 5 % increase | 1.06 | 0.588 | 1.910 |
| Sex | 426 | 1.4344 | 0.797 | 0.07 | Male vs. female | 4.2 | 0.881 | 20.00 |
| Soil lead | 426 | 1.2222 | 0.323 | 0.0002 | 500 ppm increase | 3.395 | 1.802 | 6.393 |
Table 12. Multiple Logistic Regression
Results for 376 Medicaid Children, Ages 0 to 6 Years, for 1997 to 2002 CLPPP
Data for El Paso, Texas, Matched to 2003 EPA Data on Soil Sampling Model Outcome
Is Confirmed Elevated Blood Lead Status (10 µg/dL)
Soil Lead as Test Variable–Controlling for Child's Age, Child's Sex, Housing,
Poverty, and Immigration
| Parameter | DF | Coefficient Point Estimate | Standard Error | p-value | Change | Adjusted Odds Ratios | 95% Confidence Intervals | |
| lower | upper | |||||||
| Intercept | 1 | -4.7508 | 0.6629 | <.0001 | ||||
| Soil lead | 1 | 1.505 | 0.586 | 0.0102 | 500 ppm | 4.504 | 1.428 | 14.202 |
| Sex | 1 | 0.6321 | 0.4267 | 0.1385 | male vs. female | 3.541 | 0.665 | 18.856 |
| Child's age | 1 | 2.3465 | 1.1082 | 0.0342 | ||||
| Child's age squared | 1 | -0.3456 | 0.1734 | 0.0462 | ||||
| Age of child's housing | 1 | 0.00439 | 0.0196 | 0.8224 | ||||
| Percentage of population in block group living below poverty level | 1 | 0.0047 | 0.0386 | 0.903 | ||||
| Percentage of population in census tract who Immigrated from Mexico in 1990-2000 | 1 | -0.00742 | 0.0918 | 0.9355 | ||||
Table 13. Multiple Logistic Regression
Results for 376 Medicaid Children, Ages 0 to 6 Years, for 1997-2002 CLPPP Data
for El Paso, Texas, Matched to 2003 EPA data on Soil Sampling. Model Outcome
Is Confirmed Elevated Blood Lead Status (10 µg/dL)--Soil Lead as Test Variable,
Controlling for Child's Age, Housing, Poverty, and Immigration.
Modeled by Sex
| Males only | ||||||||
| Parameter | DF | Coefficient Point Estimate | Standard Error | p-value | Change | Adjusted Odds Ratios | 95% Confidence Intervals | |
| lower | upper | |||||||
| Intercept | 1 | -4.1457 | 0.7021 | <.0001 | ||||
| Soil lead | 1 | 1.5862 | 0.7007 | 0.0236 | 500 ppm | 4.885 | 1.237 | 19.287 |
| Child's age | 1 | 2.5646 | 1.3473 | 0.057 | ||||
| Child's age squared | 1 | -0.3568 | 0.2001 | 0.0746 | ||||
| Age of child's housing | 1 | -0.00984 | 0.0209 | 0.6376 | ||||
| Percentage of population in block-group living below poverty level | 1 | -0.00349 | 0.0466 | 0.9404 | ||||
| % of Population in Census Tract who Immigrated from Mexico in 1990-2000 | 1 | 0.0481 | 0.1079 | 0.6558 | ||||
| Females only | ||||||||
| Parameter | DF | Coefficient Point Estimate | Standard Error | p-value | Change | Adjusted Odds Ratios | 95% Confidence Intervals | |
| lower | upper | |||||||
| Intercept | 1 | -8.7306 | 4.9525 | 0.0779 | ||||
| Soil lead | 1 | 1.0192 | 1.2132 | 0.4009 | 500 ppm | 2.771 | 0.257 | 29.878 |
| Child's age | 1 | 2.695 | 4.917 | 0.5836 | ||||
| Child's age squared | 1 | -0.6399 | 1.1179 | 0.567 | ||||
| Age of child's housing | 1 | 0.0782 | 0.0534 | 0.1433 | ||||
| Percentqge of population in block-group living below poverty level | 1 | 0.0167 | 0.1259 | 0.8948 | ||||
| Percentage census tract population from Mexico 1990-2000 | 1 | -0.3336 | 0.4541 | 0.4626 | ||||
