_Adelaide Stevedoring Co Ltd v Forst_

_Adelaide Stevedoring Co Ltd v Forst_ - [2011] AATA 153 - AATA 2011 case summary — Zoe

[12]

Ms Provost said that during the 1970's her work as a dental assistant in the Army exposed her on a daily basis to mercury as a component of amalgam then commonly used for filling teeth, the amalgam being mercury mixed with an alloy. The mercury, which came in a capsule, had to be mixed by the dental assistant. This task involved tipping the mercury from the capsule onto a chamois then squeezing the chamois to remove excess moisture. Ms Provost said that quite apart from getting mercury on her hands in the squeezing process, not infrequently the mercury would spill and she would simply pick it up in her hands. She said it was also impossible to avoid touching mercury when packing the amalgam into the plunger used to fill the tooth, as fingers were used to tamp down.
Ms Provost said that in the dental unit they were seeing patients hourly every day, and many required fillings. No personal protective equipment was provided by the Army at that time, dental assistants not being issued with gloves, face masks, or protective safety glasses until about 1986 or 1987. In summary, Ms Provost said that she was exposed to mercury on a daily basis for a period of some ten years in the Dental Corp.
Ms Provost however was not aware of any problems, nor did she recall having any troubling symptoms, until a short time after she took part in a training course as part of her studies for promotion to the rank of sergeant. The episode of severe ill health that she suffered after this exercise we refer to in these reasons as "the acute episode".
The training course involved an exercise in which participants were exposed to tear gas in a confined space in a hut. The participants entered the hut kitted up in a gas mask and were then required to take the gas mask off, state their name and regimental number, and run straight out of the hut. Once out of the hut they were then to run with extended arms to disperse the gas from their clothes. Ms Provost said she could not fully recall the time involved in this exercise; it may have been seconds or minutes.
Once outside the hut, Ms Provost said her eyes were stinging and mucus was streaming from her nose. But she recovered quite quickly from the initial reaction. One to two weeks later, however, she began to feel unwell and very lethargic.
Ms Provost attended an Army doctor and was found to have very high blood pressure. After an episode of dizziness she was referred to the military hospital where she was found to have protein in her urine and was suffering serious renal disease. The specialist who treated her at this time was Dr Graham Row, a consultant nephrologist in practice since 1977.
Over the years since, Ms Provost's condition has slowly progressed, and in 2008 she underwent a renal transplant of a kidney donated by her husband. She had left the Army because of her kidney complaint in 1991, but continued dental laboratory work. She remained in the Army Reserve until discharge in January 2010.

[14]

Dr Row stated that Ms Provost had initially presented on 19 March 1990 requiring hospitalisation with symptoms including dramatic onset of headache, severe hypertension, oedema, proteinuria (the presence of excess serum proteins in the urine) and haematuria (the appearance of blood in the urine), all apparently provoked by tear gas exposure in the acute episode. He said that these features were consistent with "Acute Nephritic Syndrome", although, atypically, her kidney filtration function was not seriously impaired[2]. The biopsy in May 1990 revealed a cluster of five or six glomeruli which were completely obsolescent with marked atrophy of surrounding tubules and lymphocytic infiltration. She had lost about one third of her nephrons[3].
Dr Row made the point in oral evidence that when he was treating Ms Provost his main task was to identify her condition in order to provide optimal treatment. He was not primarily concerned with questions of causation, referring to that as being rather the 'horse that had bolted'. However he was now persuaded to the view, in the light of the research discussed by consultant occupational physician, Dr David Douglas, that Ms Provost's exposure to mercury explained the onset of her disease.
Dr Row's report dated 12 October 2010[4] was written after he was provided with Dr Douglas' report containing commentary on the research findings in the World Health Organisation report "Principles and Methods for the Assessment of Nephrotoxicity Associated with Exposure to Chemicals." So while it was true that Dr Row once had thought that mercury was unlikely to be implicated his opinion had changed. Dr Row said he had been influenced by the WHO report studies that concluded that "occupational exposure to mercury vapour can lead to subclinical renal disturbances"[5].
The WHO report specifically referred to the problems in working out a cause for end-stage renal disease because of the long latency and slow development of chronic renal failure. Dr Row cited the WHO report:

[17]

proteinuria was found again on 19 January 1987 and 10 November 1987[8] after tests were requested during routine gynaecological consultation.

Dr Row on the other hand noted that Ms Provost had no past history of hypertension during oral contraceptive use, or during pregnancy. When asked about the effect of Ms Provost's pregnancy on her suspected asymptomatic chronic renal disease, he remarked that pregnancy normally challenges pre-existing kidney disease, but the disease has to be "fairly significant" for it to produce the symptoms.
The service medical records showed that Ms Provost had no protein recorded as present in her urine on three examinations between her enlistment in 1975 and September 1979.[9] She had two Medical Board Examinations on 2 and 31 March 1981, at both of which her urine (and blood pressure) were found to be normal. Between January 1982 and September 1984 she had four more normal urinary findings.[10] Her urine again was recorded as normal for her Medical Board dated 14 January 1988.[11]
Dr Row emphasised to us that the kidney has a very limited range of responses to a wide range of injuries. He explained that if a kidney suffers more than 50% nephron loss, the surviving nephrons adapt by a damaging maladaptation of "hyperfiltration", which further contributes to the proteinuria. Heavy proteinuria indicates ongoing damage and poor prognosis. He had noted this on his observations of Ms Provost from 26 March 1990 to 27 February 2001.
Regarding Ms Provost's tear gas exposure, Dr Douglas in his report stated that he assumed that the agent used was o-Chlorobenzylidene Malononitrile (known as CS). Dr Row said he had been unable to find reports in medical literature of kidney damage resulting from tear gas exposure.
In summary, Dr Row thought that the most plausible explanation of Ms Provost's condition was that she had developed chronic renal disease from her repeated low grade exposure to mercury, particularly as a dental assistant. Its presence had been revealed by her exposure to the tear gas.

[27]

The correctness of this approach was more recently confirmed by the High Court in Roncevich v Repatriation Commission [2005] HCA 40; (2005) 222 CLR 115. A causal relationship was to be distinguished from one that was merely temporal; in other words, service in truth must be a cause, as distinct from being part of the circumstances in which a cause operates.
We would observe at the outset that the respondent did not call any medical evidence that might suggest that Ms Provost's nephrosclerosis was unrelated to her defence service, or evidence that undermined Drs Row and Douglas' conclusions. Bearing in mind that the doctors were in solid agreement on the points as we have outlined above, we are satisfied that the necessary connection between Ms Provost's condition and her work as a dental assistant is made out.
The facts of which we are satisfied are as follows. On enlistment, Ms Provost had no abnormal findings in relation to her kidneys or blood pressure, so we can accept that she was in a healthy state at that time. We accept the evidence of both doctors that chemically-caused renal disease typically produces no signs and symptoms until late in its course, unless provoked by an acute event. We are very much persuaded by the congruence of the doctors' opinions that tear gas exposure in this instance acted in that way, the doctors agreeing that although there is no evidence that tear gas is itself nephrotoxic to humans, its nonspecific chemical assault on the body would have been sufficient to produce acute signs and symptoms of Ms Provost's chronic renal failure.
We accept the doctors' evidence that between 1975 and 1990, Ms Provost's lack of signs of renal disease was consistent with progression of the disease. Occasional proteinuria should be understood, with the benefit of hindsight, as flagging the presence of an underlying disease. We accept the agreed evidence that intervening normal urine tests do not refute the continued progress of the disease, and that the disappearance of proteinuria does not of itself indicate that a patient's kidneys have recovered.
The respondent implied that the evidence here remained speculative, a matter of mere conjecture on the part of Drs Row and Douglas. That suggestion is without foundation. The doctors re-examined the facts of the case and postulated a probable explanation consistent with scientific research in the field. Hindsight enabled them to bring an understanding to disparate facts, some of which were not given proper significance at the time they occurred.
In the end it is our task to decide matters of fact and causation. It is as well in cases such as this to recall the words of Rich ACJ in Adelaide Stevedoring Co Ltd v Forst [1940] HCA 45; (1940) 64 CLR 538:

At a glance

Court

Decision date

Source

Judgment (34 paragraphs)

Provost and Repatriation Commission [2011] AATA 153 (24 February 2011)

Parties

Legislation Cited (1)

Cases Cited (5)