GULFTENE C16-18 ISOMERISED OLEFINS - NICNAS

All three tests were conducted with a synthetic drilling fluid known as SYN-TEQ supplied by
Baker Hughes Inteq. This material was described as “a brown-grey suspension of a solid in a
liquid”. The specific gravity was given as 1.244 g/cm 3 , and while the content of isomerised
olefins in the material was not specified, this may be assumed to be between 30 and 50%.
Decapod (Crustacean) Acute Toxicity Test (Test Method (Chapman JC Johnston NAL
Nelson PF Sunderman RM Thompson GB 1993)
The tests on tiger prawn were performed with WAFs prepared with nominal concentrations of
the drilling mud of 0, 1 008, 3 359, 11 196, 37 320 and 124 400 mg/L. The WAF test media
were prepared by adding the appropriate quantity of homogenised drilling fluid to seawater,
and then rolling this mixture for 20 hours to allow for assimilation of the chemicals into the
water. Following this mixing procedure the vessels were allowed to stand to allow for
solid/liquid phase separation, and the aqueous phase removed and subsequently used for the
tests. The test at each concentration was performed over a 96 hour period at a controlled
temperature of 27±1 o C in duplicate using 10 prawns in each test vessel. The test was
conducted using semi-static methodology with daily renewal of the test media. The pH and
dissolved oxygen levels were monitored throughout the test period and were always between
7.70-8.34 and 5.4-7.9 mg/L respectively.
No significant mortality was observed over the 96 hour period for the WAF of 11 196 mg/L
or lower loadings, but after 48 hours exposure to the 37 320 mg/L WAF, 45% of the animals
had died although only 30% mortality was observed for the highest WAF loading of 124 400
mg/L. However, after 72 hours exposure to the 37 320 mg/L WAF 75% of test animals had
died and after 96 hours exposure 90% mortality was recorded. The data was analysed using
the trimmed Spearman-Karber method to give the LL50 of 21 700 mg/L with upper and lower
95% confidence limits of 26 530 and 17 760 mg/L, respectively. The corresponding 96 hour
NOEL was 11.2 g/L, and these results indicate that the drilling fluid containing the new
olefins shows slight toxicity to this species of marine invertebrate. However, since the
drilling mud contains 30-50% of the olefins, these chemicals themselves may have a LL50
significantly less than 21 700 mg/L. In respect of this point, Total Organic Carbon (TOC)
analysis of the test media would have been useful in improving the LL50 estimates, but this
analytical data were not provided in the summary report.
Copepod (Crustacean) Acute Toxicity Test (Test Method (US EPA 1991)
The tests on the marine copepod were performed with WAFs prepared with nominal
concentrations of the drilling mud of 0, 1 900, 6 100, 20 600, 67 100 and 224 200 mg/L. The
WAF test media were prepared as described above. The test at each concentration was
performed in triplicate using between 20 and 30 animals in each vessel. The test was
performed over a 48 hour period, and the pH and dissolved oxygen levels were monitored
throughout the test period and were always between 7.99-8.06 and 7.5-8.0 mg/L respectively.
There was increased mortality compared with the control (which itself exhibited 4.5% deaths
among the test animals after 48 hours) at all WAF loadings, and the mortality results after 48
hours were 17.8, 15.9, 23.9, 25.7 and 35.3% at the respective WAF loadings of 1 900, 6 100,
20 600, 67 100 and 224 200 mg/L. The dose – response curve is quite shallow, and the 48
hour LL50 for this species was consequently found to be greater than 224 400 mg/L although
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