The term LD 50 refers to the concentration of a drug or chemical that will kill 50% of the population exposed to the drug. The LD 50 of Pb is 5 ppm. What is the LD 50 for Pb in ppt and ppb? The term LD 50 refers to the concentration of a drug or chemical that will kill 50% of the population exposed to the drug. The LD 50 of Pb is 5 ppm. What is the LD 50 for Pb in ppt and ppb? 5000 ppt, 0.05 ppb 50 ppt, 5000 ppb 0.005 ppt, 5000 ppb   0.005 ppt, 5000 ppm

A group of 156 heart attack patients who were regular smokers up to the time of their heart attacks were followed for ten years. Among them, 75 patients continued to smoke after their heart attacks and 81 quit after their heart attacks.  Of the 75 patients that continued smoking, 27 had a second heart attack during the ten years of follow-up, and of the patients who quit, 14 had a second heart attack during the 10 years of follow-up.    What is the risk ratio for the association between continued smoking and second heart attack? Round to two decimal places

Number of cases 30,000 OOO 25,000 20,000 15,000 10,000 5,000 Reported TB Cases and Rates United States, 1993-2019 Number of cases --Incidence rate 0 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017 2019 Year 2 90 Cases per 100,000 persons The graph above shows tuberculosis cases by year in the U.S. This graph is an example of a(n): Clustering Cyclic trend Epidemic curve Secular trend

Which of the following displays the time course of a disease outbreak?     Clustering     Cyclic trend     Epidemic curve     Secular trend