WASHINGTON — Booming online retail sales are good news for the U.S. Postal Service, but its carriers are incurring a cost: more dog bites.

Dog attacks on postal workers rose last year to 6,755, up 206 from the previous year and the highest in three decades, as internet shopping booms and consumers increasingly demand seven-day-a-week package delivery and groceries dropped at their doorstep. The high for attacks dated back to the 1980s, at more than 7,000, before maulings by pit bulls and other potentially aggressive dogs became a public issue.

Los Angeles topped the 2016 list with 80 attacks on postal workers, followed by Houston with 62 and Cleveland with 60.

The Postal Service released its annual figures Thursday as part of National Dog Bite Prevention Week, which begins Sunday. A longtime cliche of movies, dog biting of mail carriers — or at least dog chasing — is no laughing matter for the post office. Medical expenses and workers’ compensation cost the Postal Service millions of dollars each year.

Overall, an estimated 4.5 million Americans are bitten by dogs annually, mostly children. In the last year, dog attacks on carriers rose 3 percent. Still, while dog bite claims are rising, there are signs attacks may be less severe: The average cost per claim fell last year by more than 10 percent to $33,230, according to the Insurance Information Institute and State Farm. “It’s always on your mind as a carrier, ‘Is there a dog in the area and is it a threat?'” said James Solomon, a 17-year postal carrier. Officially, 2 percent of carriers were bitten last year, but Solomon says every carrier he knows has some kind of “dog experience” to tell, from outrunning to cajoling a territorial pet.