3.1. MA Communities
Fifty-four communities had complete BLL, race/ethnicity, and demographic profiles. The total population of these communities accounts for approximately 50% of the state population (3,139,064 persons). In the 54 MA communities, 79.7% of the population is white, 12.4% is Hispanic, 5.5% is black, 4.9% is Asian, and 16.2% is foreign-born. The average median household income is $61,976, 11.7% of the population falls below the federal poverty level, and homeownership rate is 59.1%.Of those aged 25 and above, 86.5% graduated from high school and 35.2% have a Bachelor’s or advanced degree.
3.2. Estimating the Expanded Pool of at-Risk Children
In order to assess changes in childhood lead poisoning risk under the CDC’s new 5 µg/dL reference value, we ranked the 54 communities in a series of binning schemes. First, to represent lead risk under the former 10 µg/dL benchmark, the BLLs of MA children were divided into bins of 0–9 µg/dL, 10–14 µg/dL, and 15–24 µg/dL, as displayed in (a). Only 0.7% of 1 to 5 year old children in MA had BLLs of 10 µg/dL or higher in 2007, a very small minority. To identify children formerly masked by the 10 µg/dL reference value, the 9–47 month-old MA population with BLLs from 0–10 µg/dL in 2007 was divided into bins of 0 µg/dL, 1–4 µg/dL and 5–10 µg/dL. Of the 99.3% of children with BLLs from 0–10 µg/dL, 10.5% of children had BLLs in the 5–10 µg/dL range. The distribution of lead poisoning risk under the CDC’s new 5 µg/dL reference value is shown in (b), which presents the BLLs of 9–47 month-olds in bins of 0 µg/dL, 1–4 µg/dL, and ≥5 µg/dL.
Figure 1 Distribution of BLLs by MA community for children aged 9–47 months in 2007. (a) Distribution of BLLs binned according to the old CDC lead reference level of 10 µg/dL. (b) Distribution of BLLs binned according to the new 5 µg/dL (more ...)
In Massachusetts, the new 5 µg/dL reference value will increase the number of children considered to have lead poisoning by 1470%. Nearly half of the examined communities will experience increased lead poisoning prevalence under the new reference value.
The ten MA communities with the highest proportion of children aged 9–47 months with BLLs ≥5 µg/dL are displayed in . Of the top ten MA communities for BLLs from ≥5 µg/dL, 40% were not included in the Massachusetts Childhood Lead Poisoning Prevention Program’s “High Risk Communities for Childhood Lead Poisoning” list, which singled out the cities in MA where lead poisoning was a large threat from 2002 to 2007 [22
] (). Further, all of the top risk communities for BLLs ≥5 µg/dL changed in their ranking when compared to the distribution communities under the 10 µg/dL benchmark displayed in (a) (see ).
Table 1 Ten MA communities with the highest proportion of children aged 9–47 months with BLLs from ≥5 µg/dL in 2007, ranked by percent of population with BLLs ≥5 µg/dL, including the cities’ rankings under the 10 (more ...)
For the top ten highest risk communities under the new CDC reference value, the proportion of young children with BLLs ≥5 µg/dL ranges from 16% to 25%. These communities’ risk rankings are strikingly different than they were under the 10 µg/dL binning scheme, with changes in rank ranging from 1 to 14. The MA CLPPP’s High Risk Communities List has become an outdated measure of lead poisoning risk.
3.3. Evolving Lead Poisoning Risk Demographics
For the new top ten MA communities at risk for childhood lead poisoning, 74.3% of the population is white, 15.9% is Hispanic, 9.5% is black, 3.2% is Asian, and 16.5% is foreign-born. The average median household income is $46,216, 16.8% of the population falls below the federal poverty level, and the homeownership rate is 50.7%. Of the population above age 25, 80.5% graduated from high school and 23.3% have a Bachelor’s or advanced degree.
Correlation analysis was completed for all 54 MA communities between community BLLs ≥5 µg/dL and the primary demographic risk factors for lead poisoning risk, including median home income, poverty rate, educational attainment, homeownership rate, and race/ethnicity. The results of the correlation analyses are offered in .
Demographic variables and BLL correlation measures for correlation of BLLs ≥5 µg/dL with demographic variables for all MA towns.
The demographic factors traditionally associated with lead poisoning risk in the United States were strongly correlated with BLLs ≥5 µg/dL in 9–47 month-old MA children. Our analysis demonstrated that income level and poverty rate have the strongest correlations with BLLs in MA (p < 0.001, r2 = 0.4). Socio-economic standing, therefore, is the strongest demographic correlate to lead poisoning rates in Massachusetts.
To assess the impacts of the expanded risk population for childhood lead poisoning on the demographic profiles traditionally associated with the ailment, we compared the average demographic risk factor values for the top 10 communities for BLLS ≥5 µg/dL with the communities on the MA CLPPP’s high-risk list for the years 2002 to 2007 [22
] (see ).
Comparison of 2007 average lead poisoning risk demographic measures from the top 10 MA communities with BLLs ≥5 µg/dL and the MA CLPPP’s highest risk communities.
For the foreign-born (p = 0.03) and white population (p = 0.05) proportions, there was a significant difference between the old CLPPP top risk communities and the new top ten risk communities under the 5 µg/dL reference value. The percent of 9–47 month-old children with BLLs ≥5 µg/dL was about 19.2%, marking a 22.3% increase over that same population proportion for the MA CLPPP’s highest risk communities (15.7%). The expanded pool of children with BLLs above the national benchmark will alter the extent of risk demographics for lead poisoning in MA. The high-risk communities newly identified by the 5 µg/dL benchmark have distinctly different social, economic, and demographic profiles than those with the highest risk under the old lead poisoning benchmark.