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.
Some experts say marijuana is detectable in the blood for up to a week among regular smokers. Despite the legalization of recreational and medical marijuana in some states, you should understand the effects of marijuana usage on your body, and you should never, ever drive after using marijuana.