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.
A urine sample (known as a urine toxicology screen) is typically used to test for marijuana exposure, and it can detect marijuana for days or weeks after use. Bloodwork can also be done to test for the amount of tetrahydrocannabinoid (THC) in the bloodstream. What to expect from urine and blood tests.