The main exposure to arsenic in New Zealand occurs in the timber treatment industry. The preservation of timber (tanalising) is carried out using a mixture of salts of copper sulphate, potassium dichromate and arsenic pentoxide. The timber is pressure injected with the preservation liquid in large pressure cylinders, after which it is stacked in the yard while still wet with preservation chemicals. Arsenic may also be encountered in the plating industry and in foundries and glassworks, and is found in some fruit tree sprays. To ensure accurate assessment of exposure to arsenic, urine samples must be collected at the end of the working shift at the end of the working week if the exposure is continuous, as the half-life of arsenic in the urine is approx. 48 hours. The method used does not measure the organic arsenic compounds present in dietary fish, samples can be collected without dietary restrictions.
The concentration of arsenic in urine generally reflects very recent exposure. The frequency of biological monitoring is thus dependent on whether the work is seasonal. For example:
Seasonal timber treatment
Initial testing should be made in the first few weeks of timber treatment. If the results are normal and adequate precautions are being taken, the tests need not be repeated until a change occurs in work patterns or environment.
Regular timber treatment
Workers should be tested at least yearly. If the results are normal and adequate precautions are being taken, the tests need not be repeated until a change occurs in work patterns or environment.
If a result is above the workplace exposure standards a sample at the beginning or the working week can be taken to exclude exposure at work due to the short half-life (approx. 48 hours) of arsenic in the urine
Lipids/Trace Metals
UAS
Recommended sampling time is POST SHIFT - the last 2 hours to immediately following the end of the working day and end of working week, after at least 4 days exposure.
Aliquot to Core laboratory for UCRN
Inorganic Arsenic
10 days
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