They're afraid of accidents. As you said, a port is a place that receives potentially dangerous products.
The residents of your riding, Mrs. Vignola, are concerned about the presence of dust released by some of the products you mentioned. The public is more or less aware that this dispute, which has been going on for 18 months, involves unskilled workers doing the work of the locked-out longshore workers. The health and safety issue does come into play, since these products can endanger the surrounding population.