A total of 1582 refugee children arrived in Massachusetts during the study period. No lead test was available within 90 days of arrival for 484 children (27%), leaving 1148 children (73%) in the analysis. Of those children, 413 had follow-up BLLs performed within 1 year of the first test. Children who did not have a lead test result available were older (71% aged 3 years and older vs 61% among those who had a BLL reported; P<.001) and were more likely to be from Africa (P<.001).
Initial Lead Levels and Children's Characteristics
Among children included in the analysis, an average of 144 children arrived each year. Yearly arrivals ranged from 80 in 2002 to a high of 249 in 2004. Most children were born in Africa (50%) or Europe and Central Asia (34%), and most (70%) lived in census tracts with older homes at the time of initial testing.
Sixteen percent of initial BLLs were elevated (). More children aged 3 years and older had an elevated initial BLL compared with younger children (P=.025). Elevated initial BLL was associated with arrival year (P<.001), ranging from 27% in 2000 to 6% in 2007, with lower BLLs in later arrival years. Summer testing (P<.001), anemia (P=.024), and pathologic intestinal parasites (P<.001) were associated with initial BLL elevation.
The prevalence ratio of initial BLL elevation for children born in Africa (most often, Somalis and Liberians) was 3.8 (95% CI=2.3, 6.1) compared with the ratio for children born in Europe and Central Asia (most commonly from the former Soviet Union and the former Yugoslavia; ). Compared with children from Europe and Central Asia, West African children had a high prevalence of initially elevated BLLs, at 36%, and an adjusted prevalence ratio of 5.6 (95% CI=3.3, 9.3) for initial elevation. Children born in the Near East and South Asia region also had a significantly elevated prevalence ratio at arrival of 3.6 (95% CI=1.9, 7.8). Children who had their first lead test in summer were nearly twice as likely to have an elevated BLL compared with children tested in winter.
Relative Risk Regression Model Prevalence Ratios for Blood Lead Level Elevation at Arrival: Refugee Children Younger Than 7 Years Who Arrived in Massachusetts From 2000 to 2007
Postresettlement Changes in Blood Lead Levels
The 413 children who received follow-up testing within a year arrived with significantly higher BLLs than children who did not receive follow-up testing, with 31.5% versus 7.4% of elevated BLLs at arrival, respectively. The geometric mean was 6.1 μg/dL (95% CI=5.7, 6.5) for those who received follow-up testing compared with 4.5 μg/dL (95% CI=4.3, 4.7) for those without follow-up testing. Children aged 3 years and older were more likely to receive follow-up testing (68% vs 60%; P=.022) compared with children younger than 3 years; children from Africa (73%) and East Asia and the Pacific (77%) were more likely to receive follow-up testing compared with children from Latin America and the Caribbean (63%), the Near East and South Asia (56%), and Europe and Central Asia (46%).
Of those 413 children who received follow-up testing, 24 (6%) had a BLL increase of 5 μg/dL or higher within that year. Among the 283 children who did not have an elevated BLL at initial testing and who received follow-up testing, 21 (7%) had a newly elevated BLL at follow-up. Children who arrived with a BLL 10 μg/dL or higher experienced a statistically significant decrease in geometric mean BLL, with a decline from 14.3 μg/dL (95% CI=13.4, 15.3) at initial testing to 11.0 μg/dL (95% CI=10.1, 11.9) at the first follow-up test (P<.001). Children who arrived with a BLL less than 10 μg/dL also experienced a significant decline (P=.02), from 4.4 μg/dL (95% CI=4.2, 4.7) to 4.1 μg/dL (95% CI=3.9, 4.3).
Comparisons With Massachusetts Children
The rate of BLLs newly 20 μg/dL or higher was significantly higher among refugee children compared with the population of children living in high-risk communities in Massachusetts (; P<.001). Compared with children in high-risk communities in Massachusetts the risk ratio for having a BLL newly 20 μg/dL or higher among refugees with follow-up was 12.3 (95% CI=6.2, 24.5).
TABLE 3 Rate Ratios for Incident BLLs ≥20 μg/dL With Venous Confirmation Among Refugee Children Aged 6 Months to 72 Months Who Arrived in Massachusetts From 2000 to 2007 Compared With Local Massachusetts Children in General and Those Living in (more ...)
Conditional Risk Model
Follow-up ranged from 11 to 2437 days (6.7 years), with a median of 443 days (1.2 years; ). To further explore the effect of birth region, we ran the same model as in , but using only children born in Africa or Europe and Central Asia. The hazard ratio associated with African birth in that model was 1.5 (95% CI=1.0, 2.1; data not shown).
Hazard Ratios Modeling Time to 2 μg/dL Increases in Blood Lead Levels Over Time in the United States: Refugee Children Resettled in Massachusetts, 2000–2007
Older median housing in a child's census tract of residence at the time of blood lead testing was associated with a hazard ratio of 1.7 (95% CI=1.2, 2.3) for a 2-μg/dL increase in BLL between any 2 lead tests. When housing age was entered into the model as initial housing age, rather than as a time-varying covariate, the hazard ratio was 1.2 (95% CI=0.8, 1.8).
As with the model of initial BLLs, season of testing was significantly associated with time to increase in BLL, with a hazard ratio of 2.3 (95% CI=1.7, 3.0) associated with lead tests performed during the summer months. Anemia at arrival was also associated with a significantly increased hazard ratio of 1.9 (95% CI=1.4, 2.5), whereas the remaining covariates (age, pathologic intestinal parasites, initial BLL, venous blood draw at follow-up testing, and nutritional parameters) were not.