Travelers on the Mexico City subway system often blame authorities for broken-down escalators at subway stops, but Metro officials have another explanation：vast amounts of pee.
Somehow, urine is penetrating and corroding the drive wheels and mechanisms of the escalators. The Metro system had listed "corrosion due to urine" as one of the top five causes of escalator breakdowns.
Fermin Ramirez, the system’s assistant manager for rails and facilities, said riders appear to be urinating on escalators at off-peak hours and lightly used stations.
Most stations have no public bathroom facilities, a fact Twitter users were quick to point out, noting there are not even any pay toilets.
Of the system’s 467 escalators, 22 are out of service on any given day. The biggest problem, subway authorities admit, is that the many escalators are old, or have been damaged by rough use.（AP）
breakdown：名詞，故障；破裂。例句：She is haunted by the trauma of marriage breakdown.（婚姻破裂的創傷讓她憂愁不堪。）
penetrate：動詞，穿過；滲透。例句：The aroma of baking cakes penetrated into the room.（烤蛋糕的香氣滲進房裡。）
corrode：動詞，侵蝕；腐蝕。例句：Rain water corroded the statue.（雨水腐蝕雕像。）