Neurobehavioural changes and persistence of complaints in workers exposed to styrene in a polyester boat building plant: influence of exposure characteristics and microsomal epoxide hydrolase phenotype

Abstract

Objectives-To investigate neurobehavioural eVects and the persistence of complaints in workers exposed to styrene relative to exposure characteristics and the enzyme microsomal epoxide hydrolase (mEH) activity. Methods-A cross sectional study was performed in a retrospective cohort of workers of a polyester boat building plant 3 years after the main activity shut down in 1989. Workers still currently exposed to a much lower concentration of styrene in air than before (n=27) and formerly exposed workers (n=90) were compared with matched control workers (n=64). Currently and formerly exposed workers laminated 4700 and 3610 hours on average at mean exposure to styrene concentrations of 148 and 157 mg/m 3 respectively. A structured neurological anamnesis into former and present complaints, the NSC-60 questionnaire, and computer assisted neurobehavioural tests (NES) were administered. The mEH phenotype activity was measured in lymphocytes with a novel gas chromatography-mass spectroscopy (GC-MS) method. Results-For the period before 1989, currently and formerly exposed workers reported more complaints than control workers which related well with the mean exposure to airborn styrene concentration (p=0.03). Most complaints disappeared after the end of exposure, although the chest, equilibrium, and somatic category scores of NSC-60 and the number of workers reporting diminished sense of smell remained increased in formerly exposed workers (p<0.05). Symbol-digit substitution and digit span forwards test results were worse in currently and formerly exposed workers (p<0.01). In the combined group of currently and formerly exposed workers, the symbol-digit substitution and colour-word vigilance results related well to duration of exposure (p<0.01 and p=0.03) and mEH phenotype activity (p=0.01 and p=0.05), whereas the digit span forwards results only showed associations of borderline significance (duration of exposure (p=0.08) and mEH phenotype activity (p=0.08)).Conclusion-Most subjective symptoms were reversible but some persisted after the end of exposure to styrene, whereas dysfunction of visuomotor performance and perceptual speed seemed to persist. Duration of exposure at lamination tasks and the interaction, duration of exposure×concentration of exposure, were found to be the best predictors of worsening visuomotor and perceptual speed performances. Activity of the mEH phenotype may play a modulating part in styrene neurotoxicity. The results suggested that less than 10 years of exposure to atmospheric styrene at an average concentration of 155 mg/m 3 may result in persistent neurotoxic eVects. (Occup Environ Med 2001;58:103-112)

Effects of long-term low-level solvent exposure on cognitive function

“…Only in such cases persistent cognitive de cit remained a erwards [12,14] and the presence of de cits in neuropsychological testing shortly a er the intoxication predicted a bad prognosis [12,15,16]. Long-term exposure to low airborne exposure concentrations is likely to produce slight pre-narcotic or irritation symptoms such as headache, nausea, inappropriate laughing or angriness, dizziness, imbalance and eye irritation [12,17]. In addition, as for acute intoxications, chronic exposure conditions may lead to cortical and subcortical atrophy on CT-scan and di use diminished blood ow on Single Photon Emission Tomography (SPECT) examination [12,18].…”

Symptom screening in detection of occupational solvent-related encephalopathy

“…The Finnish criteria for CSE are extensive exposure to solvents (minimum of six OEL years) usually constituting more than 10 years of everyday exposure at work and findings of encephalopathy with cognitive dysfunction. All diagnosed cases fulfil the criteria for toxic encephalopathy type 2B according to the classification by the International Solvent Workshop (Cranmer and Goldberg 1987) or class II with objectified cognitive dysfunction of the WHO criteria (WHO 1985).…”

“…These studies have employed Euroquest (EQ) (Karlson et al 2000;Deschamps et al 2001;Carter et al 2002;Chouaniere et al 2002;Rouch et al 2003;Kaukiainen et al 2004a); Questionnaire 16 or 18 (Q16 or Q18) (Lundberg et al 1997;Nasterlack et al 1999;Ihrig et al 2001;Nordling Nilson et al 2007); and other symptom questionnaires designed for neurotoxicological settings (Kiesswetter et al 1997;Viaene et al 2001;Schofield et al 2006). In the context of symptoms, clinical investigations other than neuropsychological testing are seldom reported (Lundberg et al 1995;Nasterlack et al 1999;Attia et al 2006).…”

“…The main adverse outcome is chronic solvent encephalopathy (CSE), known also as the painters' syndrome (Arlien-Soborg et al 1979). The manifestations range from reversible symptoms of memory, concentration and mood to a psycho-organic syndrome (WHO 1985) resulting in disability to work. There is no effective therapy.…”

“…The study population consisted of active workers in the construction trade among whom highly significant associations between long-term solvent exposure and cognitive symptoms have been reported (Kaukiainen et al 2004a). Symptom questions considered as reflecting the hallmark of neurotoxic symptomatology in CSE were chosen (WHO 1985;Cranmer and Goldberg 1987;Edling et al 1990;Juntunen 1993). Respondents with the highest symptom scores regardless of their occupation (construction painter and carpenter) and exposure were invited for clinical examination.…”