Nearly every American consumer staple, from fresh produce and baked goods to household supplies and medical equipment, has been packed at some point in lightweight, flexible plastic sacks, known in the industry as poly bags. Elevated gas prices have already given U.S. consumers a sense of how the U.S.-Israeli war with Iran can impact their wallets when crude oil prices increase. But the downstream cost increases across products further along the supply chain are only beginning to be calculated. The price of polyethylene, a synthetic resin derived from petroleum and natural gas and used to make plastic packaging, has soared alongside oil prices. Last year, the Middle East accounted for around 42% of global exports of polyethylene, according to data from the polymer and chemical analysis firm ITP. With oil tankers effectively barred for weeks from transiting the critical Strait of Hormuz — the only way to reach the global market — plastic packaging producers have seen their costs skyrocket.…