WARSAW, Poland (AP) _ An emergency airlift of privately donated U.S. aid arrived here today carrying milk products, vitamins and iodine tablets for Poles in the wake of the April 26 Soviet nuclear power accident.

The specially chartered Boeing 747 touched down at Okecie Airport shortly after noon following a flight from New York. It was carrying goods collected by Americares, a private, non-profit agency based in New Canaan, Conn.

Americares officials estimated that the shipment is worth about $1.5 million. It will be distributed by the Roman Catholic Church in Poland.

''We want the Polish people to know that somebody does care and has compassion for their problems,'' said Edward Piszek, a Polish-American businessman from Philadelphia, Pa., and chairman of the Polish section of Americares.

Piszek, interviewed at the airport's arrivals lounge, said Americares had responded quickly to a request for emergency aid submitted a week ago by Bishop Czeslaw Domin of Katowice, the head of the Polish episcopate's charity commission.

Jan Wydro, an Americares official, said the aid shipment included 100,000 pounds of protein-enriched dried milk, 60,000 pounds of sterilized long-life liquid milk, 1.3 million multi-vitamin tablets and 600,000 doses of potassium iodide, which can protect people from some harmful effects of radiation.

The plane also carried several purifiers to remove radioactive particles from water, Wydro said.

Government officials earlier this week said increased radiation in Poland as a result of the disaster at the Chernobyl nuclear plant in the Ukraine did not pose a danger to Poles, but they have taken precautionary steps to prevent possible radiation poisoning.

A special government commission set up to monitor the effects of the accident said on Friday there had been ''a significant drop'' in the contamination of Polish milk, the only food product in which radiation levels had been reported to exceed emergency levels requiring precautionary measures.

The commission also said rationing of powdered milk would be expanded to cover all children under age 3. Rationing of powdered milk for infants under a year was introduced last week after people quickly bought out store supplies.

Government spokesman Jerzy Urban told a Warsaw news conference on Tuesday that the Polish government was grateful for offers of assistance from the West, but that the aid was not needed.