Prices in the Asian ethylene markets fell in the week endedMay 3, with several participants citing weak downstreamfundamentals.With production margins on key derivatives such aspolyethylene, styrene monomer and polyvinyl chloride remainingin negative territory, buyers remained sensitive to ethylene pricesas they struggled to maintain profitability.A fall in naphtha prices for the second consecutive day lentlimited support to the market, with a producer saying productionmargins on ethylene remained eroded as the spread betweenethylene and naphtha stayed below $200/mt."Yes, naphtha prices have fallen, but so have ethylene prices.The spread between ethylene and naphtha is still very weak andprofitability is low, but cargo is still available so sellers don't havemuch of a choice," said a producer in Northeast Asia.A deal done early in the week at $870/mt CFR Northeast Asiaweighed on sentiment, with buying...