Findings
Families who participated in the investigation received their individual child’s or children’s blood lead results in the summer of 2014 (results were mailed out within two weeks of the child’s blood sample collection). Families who participated in the investigation received their individual environmental sampling results by mail in December 2014. CDC/ATSDR shared preliminary study findings pdf icon[PDF – 392 KB] via a factsheet, website update, and community meeting in September 2015. In the fall 2017, a summary of the final study findings was shared via a factsheet, website update, and community meetings/outreach. The final report pdf icon[PDF – 17 MB] and journal articleexternal icon are now available.
Blood Lead Results
Children living in the investigation area are more likely to have blood lead levels equal or above most children’s levels. If a child has 5 or more micrograms of lead per deciliter of their blood (µg/dL), they have an elevated blood lead level. This is called a reference value, and it’s the measurement that CDC uses to identify children with elevated blood lead. About 2.5% children in the United States have a blood lead level equal to or above 5 µg/dL.
A total of 104 children provided a blood lead test for the study. Here’s what the blood tests showed:
- The geometric mean (which is a special type of average) was 2.0 µg/dL.
- About 12.5% of the children from the study had an elevated blood lead level of 5 µg/dL or above.
- Children with elevated blood leads were more likely to:
- Live in or regularly visit a household built before 1900
- Live in or regularly visit a household with a high dust lead result in the entryway
- Be enrolled in a government medical insurance program (Medicaid)
Children in households with two or more elevated environmental lead samples (such as front door dust and soil) were more likely to have elevated blood lead compared to children in households with one or no elevated environmental lead samples. Children with an elevated blood lead level were more likely to stay in households with an elevated level of lead in dust by the front door.
We evaluated the relationship between elevated blood lead levels and elevated environmental sample results.
- If a household had two or more elevated environmental results (soil, dust or water), the children were more likely to have an elevated blood lead level.
- Previous research has established that interior dust lead is known to be associated with elevated blood lead levels. Entryway dust is an integrated measure of dust contributed from both interior and exterior lead sources. It was not possible for us to identify whether the lead found in the dust in our study households was from interior or exterior sources.
Living close to a former lead emitting facility did not increase the chance of a child having an elevated blood lead level.
We evaluated if children living close to a former lead emitting industry were more likely to have elevated blood lead results compared to children living farther away from a former industry. The study area included at least twelve suspect historic lead-emitting point sources of interest (see Figures 1 and 2).
- Household proximity to any former lead emitting facility did not result in higher blood lead levels.
- Environmental samples collected from households near former lead emitting industries were not higher than samples collected from households farther away.
Figure 1: Blood lead sampling results from the 2014 study area, Philadelphia, PA1
1Households surveyed are not shown in their true locations. We created this figure by offsetting each surveyed home in a random direction and a random distance up to 800 feet. This method retains the general pattern of the actual distribution and preserves the confidentiality of study participants.
NOTE: The study and the City of Philadelphia use different methods to identify, collect, and, report childhood blood lead data. These data are not directly comparable and caution should be exercised in drawing conclusions. Further, a limitation of our study is that it is based on a small number of participants.
Environmental Results
We considered lead levels in soil, dust and water to be high if they were above EPA’s guidance levels. Lead from all environmental sources (for example, soil, water, etc.) contribute to a child’s total lead exposure. Elevated levels of lead in soil and dust often happen at the same time. Because of this, it is difficult to know if a child’s elevated blood lead is due to lead in the soil or the dust.
- Overall, soil lead and household dust lead were higher in the households in our study than expected. This may be due to multiple lead contributing factors such as old housing stock and household renovation activities.
The majority of households in our study had elevated levels of lead in their soil. Elevated soil lead, by itself, was not found to be a risk factor for elevated blood lead.
- We evaluated the levels of lead found in the soil. We also evaluated if children living in households with elevated lead in soil were more likely to have elevated blood lead levels. 71% of households had soil lead levels exceeding EPA’s guidance level of 400 parts per million (ppm) used for exposed soils in children’s play area.
- Soil and street dust can be transported inside the home and contribute to interior house dust. Almost a third of our study soil samples were collected from yards that were at least partially covered with concrete. This may have reduced the potential for tracking contaminated dust/soil from outside into the household.
Table 1 below describes:
- the environmental samples we collected for this study,
- what is considered an elevated level for each type of sample,
- how many of the samples in this study exceeded the elevated level,
- the range of lead that we detected in the samples, and
- the average (or “mean”) level of lead we found in the samples.
Table 1: John T. Lewis 2014 Community Blood Lead Research Study Summary of Environmental Sample Results
| Environmental Sample Type | Number of Samples | Elevated Lead Level Definition | Number of Samples Exceeding Elevated Lead Level | Minimum and Maximum Concentrations Detected | Mean |
|---|---|---|---|---|---|
| Soil | 70 | *400 ppm | 50 (71%) | 40 – 7,700 ppm | 760 ppm |
| Water | 116 | **15 µ/L | 0 | Non-detect – 3.9 µg/L | N/A |
| Dust Floor (Front Door) |
98 | *40 µg/ft² | 24 (25%) | 5.2 – 2,323 µg/ft² | 66 µg/ft² |
| Dust Floor (Child Play Area) |
71 | *40 µg/ft² | 20 (28%) | Non-detect – 632 µg/ft² | 50 µg/ft² |
| Dust Window (Child Room) | 94 | *250 µg/ft² | 13 (14%) | Non-detect – 18,000 µg/ft² | 396 µg/ft² |
*Definition of elevated soil and dust wipe sample results are EPA’s standards under the Lead Renovation, Repair and Painting rule
**Definition of elevated water result based on EPA’s action level for lead under the Lead and Copper rule
Figure 2: Soil lead sampling results from the 2014 study area, Philadelphia, PA1
1Households surveyed are not shown in their true locations. We created this figure by offsetting each surveyed home in a random direction and a random distance up to 800 feet. This method retains the general pattern of the actual distribution and preserves the confidentiality of study participants.
NOTE: The study and the City of Philadelphia use different methods to identify, collect, and, report childhood blood lead data. These data are not directly comparable and caution should be exercised in drawing conclusions. Further, a limitation of our study is that it is based on a small number of participants.