Wɔbɔɔ Michael Hart, a ofi San Diego, sobo sɛ wadi mmara a U.S. aban ahyɛ a wɔde rebɔ ɔhyew-nsuo mframa no ano. Ɛnyɛ mmara sɛ wɔde hydrofluorocarbons (HFCs) bɛba ɔman no mu bere a wonni tumi krataa soronko a Environmental Protection Agency (EPA) de ama no. Wɔbɔ Hart sobo sɛ ɔtɔre adwoa wɔ Mexico na ɔde wɔn kɔ United States denam wɔn a ɔde wɔn siee ntankɔso ne nnwinnade mu.