TFA - on page 6, I realize it is difficult - says that the the explosions were caused by aluminum dust filling the air which was not properly ventilated. According to the article, these factories are not "hyper-clean or hyper-organized."
The article is singling out Apple, but it also contrasts their attitude to the attitudes of HP and other companies which manufacture electronics goods in China.
These factories can have multiple parts. Final electronics assembly - the most photogenic stage of operations - tends to be done in clean, well-lit, well-organized, air-conditioned spaces by young women (age 16-20) wearing color-coded paper hats (you don't want aluminum dust or dandruff getting on your circuit boards). But some of the earlier manufacturing stages where you mold plastic or cut metal to make an outer case shell (that is an eventual input to the later process) can be hot and dark and grimy and smelly.
My main point here, though, is that none of this is anything new. Chinese factories are continuing to abuse their workers to increase Western profit margins. Short of completely reforming the Chinese government, what's the alternative? Employing Americans instead so that even more Chinese people starve?
Again, I hate to act like I read the entire article (and I'm now realizing that I probably could have in the time it took to type this out), but I just saw a lot of extreme language.