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Safeguard OSH Solutions - Thomson Reuters

Safeguard OSH Solutions - Thomson Reuters

Alert24 - Safeguard Update

Toxic fingerprints

Toxic fingerprints
Article Type:
Publication Date:
New Zealand

Neuropsychological assessment can be useful in the diagnosis of workers' chronic solvent toxicity health issues, and therefore their claims for compensation, says a psychologist.

Ralph Schnabel outlined a cognitive profile of solvent neurotoxicity at an Australian and New Zealand Society of Occupational Medicine conference in Wellington. Schnabel, of the Department of Psychological Medicine at the University of Auckland, says there are clear toxicity fingerprints, and chemical exposures can result in a cluster of potential problems.

He notes the many ways a person can be "poisoned" and end up with damage to the structure and function of the nervous system. They include drug and alcohol use, medical treatments like chemotherapy, and occupational exposures.

Occupational exposures were associated with a large number of employment areas like painting, panel beating, working in industrial plants and chemical laboratories, and beauty therapy. Workers for pesticide manufacturers, printing industries, chemical and petro-chemical industries, and those who used benzene or benzene products in their jobs were also at risk.

Schnabel says neural function can be compromised by toxic chemicals which affect the nervous system. Symptoms of neurotoxicity include muscle weakness, tremors, and loss of sensation and motor control. Behaviour can be impulsive and fluctuating, with signs of anxiety and depression. But a standard MRI scan will show nothing, he says.

Schnabel says toxicity assessments are complex, and based on cognitive tests called neuropsychological assessments. They will see whether, or to what degree, cognitive functions are affected, and whether the cognitive changes are consistent with neurotoxic brain damage.

The testing targets each brain area, to build a cognitive profile based on performance of an individual against norms. This can show specific diagnostic fingerprints for conditions ranging from solvent toxicity to traumatic brain injury, Alzheimer's and depression.

In applying this to compensation claims, it is obviously important to find out whether the problems are work-related, or due to the worker's personal life - the historic nature of exposures can make this difficult.

Schnabel says functions of the brain are tested which are important for assessing whether there are neurological problems. A typical profile for solvent toxicity is based on certain markers. "You can obtain a cognitive profile based on performance ... the profiles are specific, like fingerprints, and there are particular profiles for solvents."

Cognitive testing for acute and chronic exposure to solvents looks for a significant decline in attention, complex concentration, sustained attention, new learning, information retention, planning, abstract thinking, flexibility and mood regulation. "What is characteristic is a drop-off in concentration the more complex a task is."

Cognitive functions which are not affected include overall intelligence, processing speed and simple concentration.

Schnabel adds there are complicating factors to the assessments, and a number of variables have to be considered. For instance there are thousands of different solvents and solvent cocktails, of which each may cause different damage.

Variables can also include age and vulnerability to toxic effects. The toxic exposure of chemicals is worse for a person with previous brain injuries, and not all people are affected in a similar way depending on their genetic make up.

Schnabel says there are questions around dosage, whether the exposure is fleeting or prolonged, and whether it occurs in a ventilated or unventilated area.

Confounding factors in the assessment can include whether the person suffers from depression, anxiety, or an alcohol disorder. Nausea, headaches, fatigue or chemical sensitivity at the time of the testing can also interfere with the results.

Schnabel stresses that neuropsychological testing is not a stand-alone tool, and an overall assessment requires a multi-disciplinary approach, looking at exposure and medical data to control risks around false positive or false negative judgements.

He says if the toxic exposure is short, there is more likely to be a substantial and speedy recovery. "There is a less optimistic outcome for chronic exposure."


People Mentioned:
Ralph Schnabel
Organisations Mentioned:
Australian and New Zealand Society of Occupational Medicine
Reference No:

From Alert24 - Safeguard Update

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