Apple's iPad and the Human Costs for Workers in China The explosion ripped through Building A5 on a Friday evening last May, an eruption of fire and noise that twisted metal pipes as if they were discarded straws. When workers in the cafeteria ran outside, they saw black smoke pouring from shattered windows. It came from the area where employees polished thousands of iPad cases a day. Two people were killed immediately, and over a dozen others hurt. As the injured were rushed into ambulances, one in particular stood out. His features had been smeared by the blast, scrubbed by heat and violence until a mat of red and black had replaced his mouth and nose. "Are you Lai Xiaodong's father?" a caller asked when the phone rang at Mr. Lai's childhood home. Six months earlier, the 22-year-old had moved to Chengdu, in southwest China, to become one of the millions of human cogs powering the largest, fastest and most sophisticated manufacturing system on earth. That system has made it possible for Apple and hundreds of other companies to build devices almost as quickly as they can be dreamed up. "He's in trouble," the caller told Mr. Lai's father. Get to the hospital as soon as possible. In the last decade, Apple has become one of the mightiest, richest and most successful companies in the world, in part by mastering global manufacturing. Apple and its high-technology peers - as well as dozens of other American industries - have achieved a pace of innovation nearly unmatched in modern history. However, the workers assembling iPhones, iPads and other devices often labor in harsh conditions, according to employees inside those plants, worker advocates and documents published by companies themselves. Problems are as varied as onerous work environments and serious - sometimes deadly - safety problems. Employees work excessive overtime, in some cases seven days a week, and live in crowded dorms. Some say they stand so long that their legs swell until they can hardly walk. Under-age workers have helped build Apple's products, and the company's suppliers have improperly disposed of hazardous waste and falsified records, according to company reports and advocacy groups that, within China, are often considered reliable, independent monitors. More troubling, the groups say, is some suppliers" disregard for workers" health. Two years ago, 137 workers at an Apple supplier in eastern China were injured after they were ordered to use a poisonous chemical to clean iPhone screens. Within seven months last year, two explosions at iPad factories, including in Chengdu, killed four people and injured 77. Before those blasts, Apple had been alerted to hazardous conditions inside the Chengdu plant, according to a Chinese group that published that warning. "If Apple was warned, and didn't act, that's reprehensible," said Nicholas Ashford, a former chairman of the National Advisory Committee on Occupational Safety and Health, a group that advises the United States Labor Department. But what's morally repugnant in one country is accepted business practices in another, and companies take advantage of that. Apple is not the only electronics company doing business within a troubling supply system. Bleak working conditions have been documented at factories manufacturing products for Dell, Hewlett-Packard, I.B.M., Lenovo, Motorola, Nokia, Sony, Toshiba and others. Current and former Apple executives, moreover, say the company has made significant strides in improving factories in recent years. Apple has a supplier code of conduct that details standards on labor issues, safety protections and other topics. The company has mounted a vigorous auditing campaign, and when abuses are discovered, Apple says, corrections are demanded. And Apple's annual supplier responsibility reports, in many cases, are the first to report abuses. This month, for the first time, the company released a list identifying many of its suppliers. But significant problems remain. More than half of the suppliers audited by Apple have violated at least one aspect of the code of conduct every year since 2007, according to Apple's reports, and in some instances have violated the law. While many violations involve working conditions, rather than safety hazards, troubling patterns persist. "Apple never cared about anything other than increasing product quality and decreasing production cost," said Li Mingqi, who until April worked in management at Foxconn Technology, one of Apple's most important manufacturing partners. Mr. Li, who is suing Foxconn over his dismissal, helped manage the Chengdu factory where the explosion occurred. "Workers" welfare has nothing to do with their interests," he said. Some former Apple executives say there is an unresolved tension within the company: executives want to improve conditions within factories, but that dedication falters when it conflicts with crucial supplier relationships or the fast delivery of new products. On Tuesday, Apple reported one of the most profitable quarters of any corporation in history, with $46.3 billion in sales. Those sales would have been even higher, executives said, if overseas factories had been able to produce more. Executives at other corporations report similar internal pressures. This system may not be pretty, they argue, but a radical overhaul would slow innovation. Customers want amazing new electronics delivered every year. Gu Huini contributed research.