What you can't see can hurt you. That's the message from the Center for Science in the Public Interest, a consumer watchdog that found dangerous food-handling practices in the restaurant kitchens of 20 U.S. cities including Pittsburgh it studied.

Some unsafe practices produce visible results -- bugs, vermin and filthy conditions. But some of the real danger can't be seen from the dining rooms: food stored at improper temperatures, poor hygiene by employees, food from unsafe sources, improper cooking times and temperatures, and unclean preparation surfaces.

The report, titled "Dirty Dining: Have Reservations? You Will Now," says 44 percent of food-borne illness outbreaks between 1998 and 2006 started in restaurants. That's twice the rate of infection from foods cooked at home.

In Allegheny County, just 16 inspectors are responsible for checking up on 4,500 restaurants and another 3,000 establishments including retail stores, caterers, warehouses and mobile vendors. That's 469 businesses for each health department inspector. Of the 20 cities included in the study, only health department workers in Philadelphia had higher caseloads.

Most restaurants are supposed to get at least one visit a year, maybe two, and those with limited food service are inspected even less often. Health department spokesman Guillermo Cole said boosting inspections to twice per year, as recommended by the study, would require a significant increase in staffing and in the food safety budget, which is $1.9 million this year.

That's an expense worth assuming. Thorough and regular reviews of restaurant kitchens are vital to protecting public health, so the county should consider beefing up its inspection program.

The health department also should make it easier for customers to learn a restaurant's safety record.

Green stickers at entrances indicate the facilities have been inspected and have valid permits, but the decals don't say when the checks were conducted or whether there were past violations. The only way to find out is by visiting health department offices or making a written request by mail. Forget looking it up online.

In other places, an A-B-C rating system clearly tells potential patrons at a glance whether a business has an all-clear record, has had some problems or is a spot to be avoided. That would help consumers in Allegheny County, too, but the health department also needs to speed up efforts to post its restaurant reports online. Mr. Cole said the county hopes to start doing so sometime next year, but this change has been an unfulfilled promise for too long.

As more and more people dine out -- the study says the average consumer eats restaurant food at least five times a week -- the risks grow. In Allegheny County, there's plenty of room for improvement.