The threat of costly federal penalties - including the possibility of ultimately banning new businesses and barring existing ones from expanding - looms over the San Joaquin Valley.

It is against that backdrop that the San Joaquin Valley Air Pollution Control District has issued an Air Alert for Monday through Thursday. The lack of substantial breezes coupled with hot temperatures is expected to spike smog conditions to the point they could breach health-based ozone standards for more than an hour triggering millions of dollars in fines. The fine would be imposed regardless of where in the eight counties the standard is exceeded for an hour.

And while air conditions will be slightly better in San Joaquin County than in Stanislaus County and substantially better than in Bakersfield at the southern end of the air basin, pollution created in Manteca, Lathrop and Ripon drifts southward along with whatever is blown in from the Bay Area through the Altamont Pass.

An Air Alert last month was able to get enough people and businesses to alter their routines to avoid violating the ozone standard. It also helped make August one of the cleanest on record. The reason why the Air Alert was issued given such conditions is the fact the federal government has been tightening air quality standards while attaching draconian penalties if they are not met. In some categories of air pollution the San Joaquin Valley is the worst in the nation.

Residents can reduce smog-forming emissions by:

•refraining from idling when dropping off/picking up students.

•carpooling, vanpooling or alternate transportation.

•refraining from using drive-through services.

Businesses and municipalities can reduce emissions by:

•shifting operations such as lawn care to early morning or late evening.

•offering flexible work schedules.

•promoting carpools and vanpools for employees.

Other potential sanctions for failing to meet new federal air standards include losing all federal highway and federal takeover of the air quality control district.

Population in the valley has almost doubled since 1980 while emissions have been slashed by more than 50 percent.

The San Joaquin Valley during the past 10 years has:

•reduced emission from stationary sources by 83 percent.

•scored an 83 percent reduction in unhealthy days.

•recorded the cleanest winter on record in 2010 with only two unhealthy days.

•is enjoyed the cleanest summer on record with over a 50 percent reduction in the number of times ozone levels exceeded standards by 8 hours or more.

The valley averages 625 tons of nitrogen oxides being released in the air on any given day. The new standard is to get it to 80 tons a day or less.

Heavy duty trucks account for about 250 tons daily. Passenger vehicles and off-road equipment each account for about 80 tons while off-road equipment is about another 70 tons. Other off-road sources such as trains account for around 30 tons. The balances - or nearly 120 tons - are from stationary and area sources that the district has control over establishing rules. Mobile sources generate 500 tons a day and are under state and federal regulations.