Updated

Food trucks have a become a vital part of the Los Angeles culinary scene.

But their booming popularity has a dark side.

The LA Times recently reviewed restaurant data for Los Angeles County and found that about 27 percent of the food trucks operating in the area have earned less than an “A” grade in the last two years-- meaning they suffered from at least one or more sanitation violations.

That number may not seem like a lot but compared to brick and mortar restaurants—where just fewer than 5 percent of restaurants earned less than an “A”— the figure is shocking. About 18 percent of sidewalk food carts earned less than an “A” grade, according to Los Angeles County Department of Public Health data.

Experts say food trucks face unique challenges in order to comply with sanitation standards. Workers make food in a confined space (“typically less than 8 feet wide by 20 feet long,” according to the paper) and trucks don’t usually have as much equipment as a full size restaurant, which can lead to cross-contamination.

“If I serve you and I also prepare the food, there’s a little bit of a problem right there with health issues, potentially,” USC accounting professor Ruben Davila told the paper.

The Los Angeles County Department of Health says its inspection process is the same for all restaurants, food trucks and carts. Each eatery is scored on a 100 point scale, where points are deducted for major, minor, and low-risk violations. Only 10 points can be lost before falling below an “A” grade. Some of the biggest violations found include rodent infestations, improper storage temperatures, contaminated equipment and poor personal hygiene.

Some food truck operators say it’s difficult to adhere to the strict sanitation standards.

“It’s not as simple as it seems,” Tacos Ariza employee Isabel Ariza told the LA Times. “It’s hard to keep everything in one compact space. They really expect a lot from us. We try our best to be prepared but [inspectors] always try to find something. It’s hard to get an A grade.”

Tacos Ariza received a C on a health inspection in early March, with inspectors citing a variety of issues including employees failing to wash their hands or use gloves and unclean food preparation spaces within the truck..

Inspections are random, but an owner can also request and pay for a re-inspection within 12 months after the initial random inspection.

According to the investigation, the health department has shuttered more than 70 food trucks in 2016—about 4 percent of all trucks inspected. Most of trucks were allowed to reopen after passing follow-up inspections but the report sheds new light on the drawbacks of the mobile restaurant industry.