It was concluded that presence ofcannabinoids in urine or blood is not unequivocal proof of active cannabissmoking. Giardino 25 26 found THC-acid levels of up to 30-50ng/ml from passive-exposed subjects, and recommended a threshold of 65ng/ml to differentiatebetween active and passive smoking of cannabis.ticht & Kaferstein 20 estimated that the blood THC concentrationsproduced in a 70kg person smoking 15mg THC would peak at 7-8 minutes,after 30 minutes between 14-42ng/ml, and at 60 minutes between 7.5-14ng/ml.3.3 McBay 21 compared THC and THC-COOH levels in a study involving smokedmarijuana cigarettes.
Calculation Using An ovulation Calendar: 1  The first day of a period is considered as day 1. 2  Usually on day 14, the egg is released and is waiting for the sperm to fertilize it. 3  The egg has a lifespan of just 12 to 24 hours whereas a sperm can last for about 72 hours in a woman.
1 Your fertile days start 5 days before ovulation and end on the day of ovulation. 2  This method works if your menstrual cycle is regular, because then you will ovulate on a certain day of the month.3  But very few women have regular 28-day cycles. For the calendar method, you guess your next ovulation time after recording your last few months of menstrual cycles. 2  From the record, you guess which days of the month you are most likely to ovulate (be fertile). 3  Your fertile days start 5 days before ovulation and end on the day of ovulation.