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
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
If urine results are elevated (above the Biological Exposure Index), and it is unclear what the source of the potential exposure is, then the laboratory suggests the following protocol is followed:
Do a follow-up test at the end of a further working week, then re-test on the following Monday (after 48 hours of non-exposure coupled with avoidance of shellfish). The expectation is that the concentration would halve and may fall under the recommended limit.
Shellfish avoidance should then continue. Further testing at the end of the next working week should give a gauge of the effect of working practices and the requirement for any adjustments.
Note: The half-life of arsenic is in the order of 48 hours.
Methyl compounds (eg DMA from shellfish) can contribute to reported inorganic arsenic levels.Collect at end of shift at end of the working week for industrial exposure.
Ambient (8 - 24 degrees Celsius)
Chilled (2 - 8 degrees Celsius)
The urine pottle used for specimen collection must be shown to be free of Arsenic contamination. Industrial samples collected at the end of working week. Inorganic arsenic levels are not affected by organic arsenic of dietary origin (i.e. fish). Urine Chromium can be done on the same sample.
Courier to lab ambient or chilled.
Reports issued by Canterbury Health laboratories will have results along with current Normal population Reference Intervals (RI).
For interpretation against Biological exposure indexes (BEI) please refer to the latest Worksafe’s : Biological Exposure Index (BEI) review.
See link in “Additional Information” tab below for Workplace Exposure Standards on the Worksafe.govt.nz website
Normal non exposed level <0.47 umol/L
0 – 0.02 umoL/mmoL creatinine
Biological Exposure Index for inorganic arsenic and its methylated metabolites is 0.47 umol/L (35ug/L)
Workplace Exposure Standards 2018
Column exchange chromatography, ICP-MS analysis of the inorganic fraction.
$59.88 (Exclusive of GST)
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