I need assistance with the following questions epidemiology.

1."Objectives. We investigated whether foreign birthplace and residence were as-sociated with an increased risk of childhood lead poisoning.

Methods. We conducted a XXXXXXXXX study among New York City children (mean age=3 years) tested for lead poisoning in 2002 (n=203 pairs). [Those with positive results were matched to children who were negative] Children were matched on age, date of test, and residential area. Blood lead and housing data were supplemented by a telephone survey administered to parents or guardians. Conditional logistic regression analysis was used to examine the relationship of lead poisoning status to foreign birthplace and time elapsed since most recent foreign residence after adjustment for housing and behavioral risk factors.

Results. Both foreign birthplace and time since most recent foreign residence had strong adjusted associations with lead poisoning status, with children who had lived in a foreign country less than 6 months before their blood test showing a particularly elevated risk of lead poisoning relative to US-born children with no foreign residential history before their blood test (XX = 10.9; 95%confidence interval [CI] = 3.3, 36.5).

Conclusions. Our findings demonstrate an increased risk of lead poisoning among immigrant children.

a.What type of study is this? (2pts)