African-American Longevity Suffered after Great Mig

This is Scientific American's 60-Second Science. I'm Erika Beras. Got a minute?
Southern Blacks who migrated north during the Jim Crow era may have avoided some social ills and done better financially than their counterparts who stayed behind,
but they were also more likely to die sooner.
That's according to a study in the journal American Economic Review.
In what historians call the Great Migration, some six million Blacks moved from the rural South to largely urban parts of the North and West.
The period is considered to extend from 1910 to 1970.
For the study, researchers looked at Social Security records of one million of the migrants born between 1916 and 1932 in eight states in the Deep South.
They found that if a black man lived to age 65 and remained in the South, his chances of reaching 70 were 82.5 percent.
If he migrated, those chances went down to 75 percent.
For black women who lived to 65, there was a likelihood of 90 percent that she would live to 70 if she remained in the South.
If she had migrated, the odds of an additional five years of survival fell to 85 percent.
The reasons for the decreased longevity in the North remain unproven.
But records show that migrants died at higher rates from cirrhosis and pulmonary illnesses, which are linked to drinking and smoking.
The new Northerners may also have been affected by industrial pollution, cold weather and the contagious diseases that tend to accompany urban population density.
Thanks for the minute, for Scientific American's 60-Second Science. I'm Erika Beras.