What was going on when I was born?

After more than a month of rumor and speculation here, the Soviet Union has acknowledged a major disaster in the western Ukraine, where more than a billion gallons of highly concentrated waste salts from a fertilizer plant spilled into the Dniester River. Rumors of serious contamination to water supplies in the region have circulated in Moscow for several weeks. After reports reached the capital that water supplies had been disrupted last month in Odessa, speculation focused on an explosion at a large ammonia processing plant near that port city. But on Wednesday the Government newspaper Izvestia carried a detailed interview with Nikolai F. Vasilyev, the Minister of Land Reclamation and Water Resources, who provided the first official account of the disaster, which occurred more than 600 miles from Odessa.

Fighting reportedly dwindled today in southern Grenada, but United States military officials said it appeared that some Cuban and Grenadian troops had taken positions in the mountainous central and northern parts of the island. Fears were expressed that protracted fighting was still in prospect to eliminate the remaining pockets of resistance. The Defense Department said in Washington that 300 Cubans had retreated into the central and northern areas ''where militia camps were known to exist.'' Adm. Wesley L. McDonald, the United States Atlantic forces commander, said the United States had about 6,000 troops on the island.

NewsAnalysis WASHINGTON, Oct. 28 - Major news organizations across the country say that the Reagan Administration's restrictions on reporting in Grenada are preventing crucial information on military activity there from reaching the press and the public. Three days after the United States and Caribbean invasion of Grenada, only small pools of reporters accompanied by military escorts are being allowed to visit the island, and they are on a set itinerary. No reporters are being allowed to remain on the island. According to Comdr. Ron Wildermuth, director of the Information Bureau of the Atlantic Command, who is in Barbados, Vice Adm. Joseph Metcalfe 3d, who heads the 20-ship task force offshore, determines daily what reporters should see in Grenada ''based on how safe he thinks it is over there.''

Along the road into town, Grenadian civilians waved timidly today as truckloads of American and Caribbean soldiers headed into this capital. The soldiers came from Queens Park, a soccer field where the United States marines have their command post. At 3 P.M. 250 men from the Caribbean contingent of the multinational invasion force had landed by helicopter at the field. On entering the capital, they immediately fanned out, ostensibly taking up policing duties from the 900 marines who had secured the northern part of the town since the invasion of Grenada began on Tuesday. Not Trained for Battle Col. Ken Barnes, the Jamaican commander of the Caribbean forces, which have come from Barbados, Jamaica, Antigua, St. Kitts and St. Vincent, said his men ''were not trained to fight battles, and our duties for the most part will center on internal security, mostly police activity, searches, patrols and interrogation.''

Text of the resolution, page 4. UNITED NATIONS, N.Y., Oct. 28 - The Security Council approved a resolution today ''deeply deploring'' the United States-led invasion of Grenada as a ''flagrant violation of international law.'' The United States immediately vetoed it. The vote, cast in the early morning hours, was 11 in favor of the resolution to 1 against - the veto by the United States.

The Speaker of the House, Thomas P. O'Neill Jr., who has generally supported President Reagan's positions in Lebanon and Grenada, turned sharply against the Reagan Administration today and called its foreign policy ''frightening.'' Mr. O'Neill's comments came as the Senate adopted, 64 to 20, an amendment declaring that the War Powers Act now applied to the fighting in Grenada. If the legislation invoking the resolution becomes law, Mr. Reagan will have to withdraw troops from Grenada within 60 days unless Congress specifically authorizes a longer time period. The shift by Mr. O'Neill, a Massachusetts Democrat, highlighted a turbulent day of debate on Capitol Hill over the course of the President's policies in both Latin America and the Middle East. In the aftermath of Mr. Reagan's televised speech Thursday night, several lawmakers rose to defend him today. A typical comment came from Representative Dick Cheney, Republican of Wyoming, the third-ranking Republican in the House.

Americans back the invasion of Grenada and marines in Lebanon but are uneasy with President Reagan in a crisis, a poll shows. Page 9. WASHINGTON, Oct. 28 - The White House said today that the Reagan Administration would withdraw American forces from Grenada in a matter of weeks ''at the outside,'' meeting its earlier estimate. But American military officials offered a more pessimistic view, saying that 300 Cubans had retreated into northern and central mountain areas where militia camps were known to exist and where a guerrilla resistance would be feasible.

The Reagan Administration is now assuming that the Iranian Government played the key role in the bombing attacks on the American marines and French troops last Sunday and will retaliate once conclusive information is collected, Administration officials said today. In another Middle East development, several officials said Donald H. Rumsfeld, who was Defense Secretary in the Ford Administration and is a friend of Secretary of State George P. Shultz, had been approached about becoming the next special envoy to the region. Another name under consideration is that of Alfred L. Atherton Jr., the departing Ambassador to Egypt. It is possible, one official said, that they might divide the task, with Mr. Rumsfeld concentrating on Lebanon and Mr. Atherton on broader peace issues.

The army general who led a coup against the Government of Bangladesh 18 months ago came to rural southeast Texas today and watched how long-grain paddy rice was sorted, milled and parboiled here at the highly automated El Campo Rice Milling Company. If it seemed odd that a man of the sword should be interested in agriculture, it was not surprising to those who understand the political realities of Bangladesh, an impoverished land where a poor harvest or food shortages can lead to enormous turmoil. ''We are trying to be self-sufficient, so we are looking at everything to find better technology to produce better rice and more rice,'' said the leader, Lieut. Gen. Hussain Mohammad Ershad, President of the martial law Government. General Ershad spoke at the Wharton County Electric Cooperative in nearby El Campo, where he and his entourage were treated to a Texas lunch of barbecued beef, beans and rice. They appeared to enjoy the food; his Texas hosts may been been rural folk, but they were diplomatically savvy enough to omit the pork ribs for the Islamic guests.

A coalition of 12 opposition parties announced today that it would take part in parliamentary elections scheduled for next May only if President Ferdinand E. Marcos gave up the power to legislate by decree and agreed to seven other demands. Former Senator Salvador H. Laurel, the president of the coalition, called the United Nationalist Democratic Organization, said in a statement that the proposals were being offered ''as an alternative to imminent violence and as a solution to the serious political and economic crisis that we face today.'' The statement was issued as thousands of women, led by the widow of the slain opposition leader Benigno S. Aquino Jr., marched through some of Manila's busiest streets to protest against the President's 18-year-old rule. The procession ended with a program of speeches by women's leaders at a grandstand in Rizal Pari, the usual site of patriotic functions staged by the Government.

The army imposed a curfew today on a refugee camp near the occupied West Bank city of Nablus after stone-throwing protesters slightly wounded an Israeli soldier and damaged two military vehicles.

The Dutch antimissile campaign has been given new momentum because of the anger over the invasion of Grenada. ''This should push people in the middle over to our side,'' said Mient-Jan Faber, head of the Interchurch Peace Council. The council is the main arm of the Dutch antimissile movement, which is preparing for a protest Saturday in The Hague. ''The whole antimissile issue is over confidence in Washington and Mr. Reagan,'' Mr. Faber said, ''and whether we, as Europeans, have any influence on what Washington or Mr. Reagan do. The message from Grenada seems pretty clear that we do not.''