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.