Industry Environment
Exposure to white phosphorous was responsible for one of the most unpleasant occupational diseases that afflicted match makers in Victorian England.‘Phossy Jaw’ (phosphorus necrosis of the jaw), is caused
by the deposition of white phosphorous within the structure of the jawbone, causing the bone to become abscessed and loose its rigidity
V: phosphorus, arsenic + antimony Inorganic phosphorous is an essential element for life, accounting for approximately 1 percent by weight of the average person. Elemental phosphorous exists as several allotropes, including red and white phosphorous. Exposure to white phosphorous was responsible for one of the most unpleasant occupational diseases that afflicted match makers in Victorian England. ‘Phossy Jaw’ (phosphorus necrosis of the jaw), is caused by the deposition of white phosphorous within the structure of the jawbone, causing the bone to become abscessed and loose its rigidity. This process is accompanied by excruciating and debilitating pain[8]. This terrible affliction could be easily eliminated by providing adequate factory ventilation or by switching to the safer red phosphorous allotrope, but it took concerted action by factory ‘match-girls’ to force through basic safer work practices in 1888.
Figure 4. Artisan miner in Tanzania mixing mercury by hand with crushed ore to extract gold. (Photo credit: Antony Benham, NERC)
governments conducted “Cold War” tests from 1953 – 1964 to model biochemical dispersion using zinc cadmium sulphide (ZnCdS). Over 4,600 kg of fine material was released into the atmosphere at selected points from aircraft and ships in the UK alone. ZnCdS was selected as an agent because fluorescent particles could be easily detected using UV lamps and the distribution mapped. It was concluded that these tests did not significantly add to the cadmium burden in the soil [6].
III: aluminium, gallium and indium The chemistry of gallium and aluminium is also very similar; gallium is extracted from smelting of aluminium ores. While aluminium is very abundant in the earth’s crust (8 percent by weight): gallium is relatively rare. Although there are no documented health effects of gallium, aluminium has been linked to some medical conditions, including (controversially) Alzheimer’s disease[7].
Suffice to say that exposure from natural sources dwarfs any potential impact from compound semiconductor processing. Indium is a relatively rare element in nature and is also believed not to pose any serious health risk.
50
www.compoundsemiconductor.net January/February 2012
Arsenic is universally recognised as synonymous with poison. Its nefarious properties were well known in antiquity and arsenic trioxide (‘white arsenic’) has been used as deadly poison ever since; 180 mg is a lethal dose[9]. It occurs as inorganic and organic compounds, with the former being considerably more toxic. It has several valence forms, which have different toxicities. The As-3
species is the most toxic form and is encountered in the fab most commonly as gaseous arsenic hydrides used for epitaxy, which require special handling. The trivalent form, (As+3
times more toxic that the pentavalent species (As+5 form and
is significantly more soluble in water. GaAs chemical polishing waste streams, being highly oxidised, contain arsenic almost entirely in the As+5
consequently are less toxic than lapping and grinding waste streams. It has been shown that GaAs wafer lapping and grinding waste streams contain significant amounts of soluble arsenic, predominantly in the trivalent form and should be handled with care.
The different behaviour and toxicity of arsenic at different oxidation states has significant environmental consequences. Arsenic can be released into groundwater if naturally occurring pentavalent aersenic in sediments is reduced to the trivalent form and unbound from iron and manganese minerals. Tens of
), is approximately fifty ) and
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