Clarence Ditlow, executive director of the Center for Auto Safety, notes there is no such thing as a small or minor recall.

The numbers have been adding up fast. Just since the beginning of this month, Japan’s five largest automakers have recalled nearly 6 million vehicles due to airbag problems. General Motors has staged more than three dozen recalls since the beginning of the year for all manner of issues impacting 20 million vehicles worldwide, nearly 18 million in the U.S. alone.

At the current pace, industry analysts anticipate the industry will soon exceed not only last year’s total of 27.96 million vehicles covered by safety-related recalls, but also the 33.01 million peak set in 2004.

Yet – or perhaps because of – the fast clip of announcements, there’s concern that millions of those vehicles will never be repaired. According to data tracked by the National Highway Traffic Safety Administration (NHTSA), an average one of every four vehicles covered by a safety recall will never be fixed.

And that adds up fast when you’re talking millions of vehicles a year. CarFax, an online service that tracks vehicle histories, estimates there are more than 36 million vehicles on U.S. roads with at least one recall-related repair not completed, some of them potentially quite deadly.

Honda, for example, reported several fatalities last year related to faulty airbags that sent shrapnel flying into the passenger compartment. At least 13 people – and likely quite a few more – have been killed in connection with General Motors’ faulty ignition switch defect.

Some of the problems might seem relatively innocuous. Kia, for example, issued a recall in February because the sticker inside the driver’s door pillar showed the wrong tire pressure ratings.

“There’s no such thing as a modest recall,” contends Clarence Ditlow, director of the Washington, D.C.-based Center for Auto Safety. Even a faulty window sticker can kill, he contends, noting that underinflated tires may be more prone to blow out or cause a vehicle to skid or roll in an emergency maneuver.

Why would owners risk their own life and limb – never mind putting family and friends in harm’s way?

Mike Rozembajgier, a vice president of Stericycle, a firm that helps large corporations manage their images, says that in a year like this one, there might be a bit of “recall fatigue.” The headlines have become so frequent that consumer almost become numb or, worse, may think that automotive manufacturers and regulators are simply crying “Wolf,” over issues that don’t really matter.

There’s also concern that owners may simply mistake the recall notice they receive in the mail as just some more junk to be ignored and tossed away, despite the large, red label.

Other owners simply procrastinate, and they’re the ones industry watchers consider the most likely to have several unattended defects with their vehicles. Considering the number of cars, trucks and crossovers impacted each year, and with the average vehicle on the road now about 11 years old, it’s common for many of them to be the target of multiple recalls before they head to the junkyard.

There’s also concern that the longer it takes for a manufacturer to stock the parts necessary to make repairs the more likely owners will simply forget to follow up. As of last week, GM service techs had reportedly completed replacing the faulty ignition switches on barely 180,000 of the 2.6 million vehicles covered by the recall. The maker is struggling to get enough parts from the supplier, Delphi, and is hoping to complete the recall by October.

GM has set a target of 100% completion for the deadly switch problem. Toyota aggressively pursued the same goal when it launched a series of recalls in 2009 and 2010 to address issues with so-called unintended acceleration.

Manufacturers have been bringing in consultants to figure out ways to boost the response rate. GM is now sending out recall reminder notices every three months. Chrysler has boosted its recall response rate from 70% to 80% in recent years by using not just “snail” mail, but also e-mail and phone call reminders.

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Makers have encouraged dealers to routinely check the corporate database when a car comes in for service to see if the vehicle has an uncompleted recall issue. Honda says that has helped it get its response rate up to more than 80%, since so many of its owners continue to use dealers for service. But, in some instances, such as last year’s airbag recall, it has also used the phone to reach out to owners who didn’t initially respond.

“Honda has always been proactive with recall notifications,” said Honda’s Detroit-based spokesman Steve Kincade. “We err on the side of caution.”

(Click Here for details on the recall of more than 3 million vehicles for airbag problems.)

Not surprisingly, experts say, the older the vehicle the less likely it is an owner will get recall work completed. Part of the problem is the challenge for manufacturers to maintain accurate databases as vehicles are sold and re-sold.

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NHTSA has also stepped up its own efforts to get recalled vehicles repaired. A motorist can go to the Safercar.gov website and sign up for alerts. The federal safety agency also uses Twitter and Facebook, as well as a new mobile app, to alert motorists.

And as of Aug. 14, all manufacturers operating in the U.S. will have to operate online databases that a motorist can search using their 17-character Vehicle Identification Number, or VIN. That information also will become available on the Safercar.gov website.