Apple may have won all kinds of kudos for removing toxics from its products, and it has publicly committed to removing conflict minerals from its African supply chain, but the company still finds itself in trouble this week over apparently widespread pollution in China.

A group of Chinese NGOs that has long been pushing Apple to improve the environmental efforts of its Chinese manufacturing partners this week published a new report finding "severe damange to the environment" from five of Apple's known or suspected suppliers. [Read Erica Gies' in-depth look at Apple's supply chain woes here.]

(If that sounds like police-speak for mafia kingpins, it's not far off from the truth: In the highly secretive world of tech manufacturing, it's difficult if not impossible to find out where companies get parts for their gadgets. The NGOs in this case spent five months identifying seven Apple suppliers.)

Among the allegations in the report:

• Meiko Electronics plant in Guangzhou, a suspected PCB supplier to Apple Inc., was found in violation of environmental rules 10 times within a few months, after what the report calls schemes "to conceal their environmental violations."

• Meiko's plant in Wuhan was found to be discharging heavy metals directly into Nantaizi Lake; copper content in a sediment sample was found to be 56 to 193 times of that in the sediment in other lakes.

• Two factories in Tongxin have taken a once-prosperous village and bought up the arable land at under-market rates, and villagers say since the factories have been built, the "village's stream that once had relatively clean water has now turned inky black." That has been coupled with a sharp rise in cancer deaths in the villages -- up from 1 in the 1970s to 11 in the 2000s.

There are many more environmental black eyes in the report, which is a detailed mix of public records research and on-site investigations. The report also looks at pollution from hazardous waste treatment facilities, one company's failure to respond to health problems suffered neighboring residents as a result of gases discharged from the factory, and others.

The reason for the NGOs' focus on Apple is several-fold: First and foremost, Apple products have become tremendously popular in China. In addition, Apple's Chinese operations are still reeling from a string of setbacks. The New York Times reports:

Last year, one of Apple's biggest suppliers was hit by a wave of worker suicides at several of its mainland Chinese facilities. And in May, an explosion and fire at a plant that made Apple products killed two people and injured more than a dozen in the city of Chengdu, in southwest China.

Also earlier this year, Apple acknowledged that 137 workers at a Chinese factory near the city of Suzhou had been seriously injured by a toxic chemical used in making the signature slick glass screens of the iPhone.

Apple responded to the report in a run-of-the-mill statement yesterday, saying in part that the company is committed to "driving the highest standards of social responsibility" in its supply chain.

"We require that our suppliers provide safe working conditions, treat workers with dignity and respect, and use environmentally responsible manufacturing processes wherever Apple products are made," the statement added.

Regardless of what the company says it's committed to, what is happening on the ground is of huge concern, not just to Apple but to any company that has a far-flung supply chain.

Can any company operating a complicated global supply chain really know what's happening at the source, all the time? Let us know your thoughts in the comments below.