Arsenic is present in the environment as a naturally occurring substance or as a result of contamination from human activity. It is found in water, air, food, and soil in organic and inorganic forms.
At first glance, it may seem difficult to explain. A difference in the lobe separation angles (LSA) of the cams can explain the difference. LSA is the Lobe Separation Angle or the number of degrees between the intake and exhaust lobe centerlines. The LSA has a direct relationship to amount of overlap on a cam.
Depending on how such a rule is implemented, a weight increase could include more legacy airplanes under the LSA umbrella, including Cessna 120s and 140s Luscombe 8Es and some of the Taylorcraft and Aeronca models that are now just over the weight line.