Ringing in the new year are dozens of changes in federal laws and regulations, many of them aimed at quenching Americans' thirst for security and a few that will make life a little more expensive.

Among the most significant of the Jan. 1 changes are a vast expansion of Medicare to cover catastrophic illnesses, faster pension-fund vesting that will benefit millions, particularly women, and tax changes reducing the government's subsidizing of purchases on credit.Others occurring slightly before the end of 1988 or scheduled early in 1989 include a ban on lie detector tests by private employers, 60-days advance notice of plant closings and large layoffs and a new law prohibiting landlords from discriminating against the handicapped and families with children.

A few of the changes are a little more esoteric, but their impact eventually may be felt by the entire population.

For example, Environmental Protection Agency regulations implementing the 46-nation ozone treaty take effect Jan. 1. The regulations don't require chemical companies to actually do anything until next July, but then they must cut their production of chlorofluorocarbon or CFC compounds by an estimated 20 percent back to 1986 levels.

The treaty is aimed at halting the depletion of the ozone layer 15 to 25 miles up, which protects the Earth's surface from ultraviolet rays. CFC compounds also contribute to the "greenhouse" effect that is warming the planet.

As a result of the regulations, consumers may notice fewer plastic food containers from fast-food outlets, thicker insulating panels and possibly even slightly harder seat cushions.

The biggest of the immediate changes is the Jan 1. expansion of Medicare coverage for 32 million Medicare beneficiaries to include catastrophic health care costs.

Prior to passage of the measure last summer by Congress - the first major expansion of Medicare in its 22-year history - the program paid full hospital bills for no more than 59 days a year.

With the changes going into effect Sunday, the beneficiary still will have to pay the first-day deductible of $560. But that charge will be assessed no more than once a year no matter how many times the patient has to be hospitalized. The other 364 days are fully paid.

That fundamental change in the hospital benefit was the cornerstone of the Medicare expansion set in motion by President Reagan in his 1986 State of the Union message.

"Let us remove a financial specter facing our older Americans - the fear of an illness so expensive that it can result in having to make an intolerable choice between bankruptcy and death," he said then.

Medicare enrollees will pay for the new benefits through a flat increase in the premium deducted from their monthly Social Security checks and an additional sliding scale premium for approximately 40 percent of the elderly who pay federal income tax.

The flat increase will be $4 a month effective immediately, climbing to $10.20 monthly in 1993. The sliding scale premium is projected to rise from a maximum of 15 percent of regular income tax liability in 1989 to about 28 percent in 1993.

Many of the Jan. 1 changes grow out of the 1986 Tax Reform Act. The biggest new benefit from that law going into effect Sunday is faster vesting in pension plans.

The maximum waiting period for employees to become fully vested in a pension is being cut in half from 10 years to five years.

However, employers can adopt an option that denies full vesting until seven years. To do so, they have to offer 20 percent vesting after three years and an additional 20 percent vesting annually until the seventh year, when it reaches 100 percent.

The Employee Benefit Research Institute estimates that the pension changes will provide a retirement stake to 2 million more workers a year.

Another tax change is that only 20 percent of personal interest payments on everything from car and student loans to credit card charges will be deductible in 1989, compared with 40 percent last year.

And while the government is now raising tax brackets, exemptions and standard deductions to keep cost-of-living raises from bumping people into higher brackets, it also is taking more Social Security taxes.

The 7.51 percent Social Security tax took a maximum $3,380 out of employee paychecks in 1988. This year the maximum amount of income subject to the tax rises from $45,000 to $48,000, raising the maximum Social Security tax that can be collected from an individual employee to $3,605.

The latest change came about just last Thursday, when the Federal Aviation Administration ordered airlines, effective Jan. 1, to either inspect by hand or X-ray all luggage checked aboard U.S. airline flights from western Europe and the Middle East.

The new inspections, prompted by the bombing of a Pan Am jet over Scotland on Dec. 21, are expected to delay passenger check-ins by about an hour.