Domestic combustion of coal for residence heating and food preparation
is pervasive in the mountainous regions of Guizhou Province, SW China.
The use of locally mined, high-arsenic (>100 ppm) coals has caused in
excess of 3,000 cases of arsenic poisoning restricted to several
villages. Samples of several high-As coals are being studied to
determine the concentrations, distributions, and form(s) of the
arsenic. This information should help us determine the source of the As
and better understand its behavior during the combustion process.
Preliminary results from selected coal samples indicate that As contents
are as high as 35,000 ppm!, on a whole coal basis. The coals contain
multiple As-bearing phases including arsenopyrite, As-bearing pyrite,
arsenic sulfide (realgar?), Fe-As oxide, As-bearing K-Fe-sulfate
(jarosite?), and As-bearing iron phosphate. Some of the organic matter
appears to be suffused with organically-bound As or contains extremely
fine (<<1 µm) particles of an As-rich phase, apparently an arsenate.
The primary path of human introduction appears to be through ingestion
of various foods dried and stored in chimneyless dwellings. For
example, the drying process increases the arsenic content of chili
peppers from background levels (<1ppm) to as much as 500 ppm. Some of
the arsenic-rich coal samples also have high concentrations of antimony
(>200 ppm), gold (almost 600 ppb), and mercury (up to 45 ppm).