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.
Cannabis & Marijuana Drug Testing. Cannabis and its active ingredient THC is tested for in most drug tests. After one-off or occasional use its break-down products or metabolites can be detected between 3-5 days after use. (1) However, THC can be detected in a chronic user up to 12 weeks after use (2) although the average is 25(3) -27 days (4). Cannabis is highly detectable a long time after use because THC lingers in the fatty tissues of the body and leaks steadily into the blood and then the urine over weeks.