The Polish government, acknowledging that fallout from a damaged Soviet nuclear reactor poses a potential hazard to human health, said today that it would issue medication to children in affected areas to protect against radioactive iodine.

In an official communique read on the evening television news, the government said it was also temporarily restricting the sale of milk to reduce the possible intake of iodine, a hazardous but short-lived component of fission wastes.

In addition, the communique warned of the "absolute necessity" of washing all fresh vegetables carefully to remove radioactive particles.

These precautionary steps followed day-long deliberations by a high-level government commission, said government spokesman Jerzy Urban.

Made up of senior military, health, energy, agricultural and environmental officials, the commission is headed by Deputy Premier Zbigniew Szalajda. The government said its commission was in "constant and direct contact" with Soviet authorities and was consulting as well with the International Atomic Energy Agency in Vienna and with Scandinavian countries, where wind-borne fallout from the Chernobyl reactor was first detected Sunday in a broad arc reaching across Denmark, Sweden, Norway and Finland.

[News agencies of other Soviet Bloc countries gave minimum of coverage to the accident, The Associated Press reported.]

Radiation measurements made by the Polish Air Force and ground units today showed a rising level of radioactive iodine. As of 3 p.m., the levels detected "could be hazardous if maintained for a longer period of time," the government statement said.

It added that later measurements showed a "receding trend" in iodine levels and no increase in other radioactive isotopes from the damaged reactor at Chernobyl, 280 miles southeast of the Polish border in the Soviet Ukraine.

Scandinavian countries, nearly three times this distance from the accident site, have reported radiation levels three to 10 times above normal background, an intensity not considered generally hazardous to health.

Because of its proximity to the Ukraine, Poland is thought to have received a heavier dose of fallout than the Scandinavian countries, with monitoring sites in the northeast quarter of the country showing the highest readings.

Initially, the government said it was here that anti-radiation tablets would be distributed to children and infants. But a later statement carried on Warsaw radio suggested that a broader distribution was planned. The statement said all children under the age of 6 in Warsaw, a city of 1.5 million, and the surrounding province would also begin receiving a one-time dose of the medication in kindergartens and nursery schools starting Wednesday morning.

The statement said there was no immediate danger from radioactive iodine and described this measure as a "precaution." The government has not said how many children were to be treated altogether. Poland has a population of 38 million.

Iodine moves readily into the food chain from grass, through cows and into man, and it tends to accumulate in the thyroid gland, where its radioactivity can lead years later to cancer. The medication that health authorities plan to distribute is designed to stimulate the excretion of iodine.

"The iodine occurring in the air can be harmful to infants, children and pregnant women," the televised statement warned. "Experts recommend that people abstain from drinking milk that comes from cows fed with green fodder."

State-run dairy enterprises and collecting stations were instructed to sell only milk from cows fed on dry fodder drawn from protected storage areas. Iodine-131 has a half-life of 8.05 days, which means that half of any given quantity becomes a harmless substances in that period of time.

Earlier today, Urban said that radioactive fallout has been detected at nearly all of 200 monitoring sites in the country. But he insisted there was no indication of a health hazard. He said the situation was "not deteriorating, and may even be improving."

This statement appeared to reflect a shift in prevailing winds toward the east and south, which would carry a plume of escaping fission wastes away from Poland and northern Europe and back toward the Soviet heartland.

The accident has posed a delicate political problem for Poland, which, like all other members of the Soviet Bloc, avoids any public statement casting a negative light on the Soviet Union. Accordingly, Urban was extremely guarded in his comments, while trying at the same time to reassure a nervous public.