The U.S. added 142,000 new jobs in September, a disappointing figure the Federal Reserve will be closely scrutinizing as it mulls the first rate hike in nearly a decade.

The headline unemployment rate held steady 5.1%. Economists had forecast 203,000 new jobs and that the unemployment rate would remain at 5.1%.

A record 94,610,000 Americans were not in the American labor force last month — an increase of 579,000 from August — and the labor force participation rate reached its lowest point in 38 years, with 62.4 percent of the U.S. population either holding a job or actively seeking one.

…In September, according to the Labor Department's Bureau of Labor Statistics, the nation's civilian noninstitutional population, consisting of all people 16 or older who were not in the military or an institution, reached 251,325,000. Of those, 156,715,000 participated in the labor force by either holding a job or actively seeking one.

The 156,715,000 who participated in the labor force equaled only 62.4 percent of the 251,325,000 civilian noninstitutional population. The last time the labor force participation was as low as 62.4 percent was in October 1977.

The Environmental Protection Agency on Thursday tightened the federal ozone standard, dismissing the concerns of powerful business groups and setting off a regulatory and legal fight that will last for the remainder of President Obama's time in office.

The agency's updated ozone regulations lower the standard from 75 parts per billion (ppb) to 70 parts per billion.

Business groups, which had pushing the administration to keep the standard at its current 75 ppb level, say the regulations will be the most expensive in U.S. history, siphoning as much as $3.4 trillion out of the economy over the next two decades.

"Today, the Obama administration finalized a rule that is overly burdensome, costly and misguided," National Association of Manufacturers CEO Jay Timmons said in a statement. "For months, the administration threatened to impose on manufacturers an even harsher rule, with even more devastating consequences. After an unprecedented level of outreach by manufacturers and other stakeholders, the worst-case scenario was avoided. However, make no mistake: The new ozone standard will inflict pain on companies that build things in America — and destroy job opportunities for American workers. Now it's time for Congress to step up and take a stand for working families."