Click on a circle in the chart to view Sham immigration records. You can find out when most of the Sham families immigrated to the United States. You can focus your search to immigration records dating from that era. Immigration records can tell you an ancestor's name, ship name, port of departure, port of arrival and destination.
Probably, however...: As my colleague dr. Pappas mentions, marijuana is almost always tested in urine rather than blood, so someone would almost certainly pass a blood test but is more likely to face a urine test.
In blood samples, cannabis can be detected for about 12 to 24 hours after consumption, with regards to infrequent users. The drug can be found in blood samples of frequent users for up to 7 days. Blood tests are not so common but are usually done in investigations of accidents and injuries.