Answer to Question 1
Originally introduced in 1919, the hard hats first used for head protection in a construction setting were inspired by the helmets worn by soldiers in World War I. Such early versions were made of varnished resin-impregnate canvas. As material technology evolved, hard hats were made of vulcanized fiber, then aluminum, and then fiberglass. Today's hard hats are typically made from the thermoplastic material polyethylene, using the injection-molding process. Basic hard hat design has not changed radically since before World War II. They are designed to provide limited protection from impact primarily to the top of the head, and thereby reduce the amount of impact transmitted to the head, neck, and spine.
Answer to Question 2
No employee may be exposed to lead at airborne concentrations greater than 50 ug/m3 averaged over an eight-hour period.
Lung Fissures, Right Lateral View
Lateral rectus
Anterior and lateral views of breast anatomy
Right Lateral View of Vertebral Column
The lateral corticospinal pathway
The traditional human karyotypes derived from a normal female and a normal male