In this dissertation, I explore how international migration and environmental pollution shape human capital accumulation and labor market outcomes.The first chapter examines how college enrollment and major choice decisions of young adults in migrant-sending countries are affected by the removal of international migration barriers. My identification strategy exploits exogenous variation in migration costs during the 2004 European Union (EU) enlargement to compare enrollment in newly admitted sending countries and incumbent destination countries. I use microlevel data from the EU Labor Force Survey and an event study framework to show that college enrollment in new states increased 15-25% in anticipation of better migration opportunities, and up to 30% once borders opened. College students in new states were more likely to enroll in college majors related to occupations with labor shortages in destination countries. To disentangle the effects of migration costs and wages on enrollment, I develop a model of college major choice with a migration option. Counterfactual policy experiments indicate that sending country enrollment is highly sensitive to migration penalties, but less sensitive to domestic college wage increases. The second chapter explores the effect of large migration outflows on local wages and the gender wage gap. I estimate the short-run net effect of emigration on real gross monthly earnings in 10 Central and Eastern European countries using a simple structural factor demand model. The model assumes that workers across education, workers within education and across age, and workers within education--age groups and across gender are imperfect substitutes. I find that the large emigration occurring due to EU accession increases average wages as much as 3.5%. In most countries, these gains are concentrated among young and highly educated female and male workers, while workers with an intermediate level of education see negligible wage gains or even losses. Finally, female workers exhibit higher wage gains than men, which indicates a possible decrease in the gender wage gap as a result of emigration. The third chapter is co-authored with Ludovica Gazze and Claudia Persico and explores the long-run spillover effects of lead. Children exposed to pollutants like lead have lower achievement in school and are more likely to engage in risky behavior. Because children interact daily in the classroom, lead-exposed children might affect the long-run outcomes of their non-lead exposed peers. We estimate these spillover effects using unique data on preschool blood lead levels (BLLs)matched to education data for all students in North Carolina public schools. We compare siblings whose school-grade cohorts differ in the proportion of children with elevated BLLs, holding constant school and peers' demographics. Having more lead-exposed peers is associated with lower high-school graduation and SAT-taking rates and increased suspensions and absences. Peer effects are larger for black students. Based on the lower likelihood of graduating high school alone, we estimate that the spillover effect of lead exposure is $9.2 billion per birth-year cohort. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]