A study of 85 painters by Mikkelsen showed that changes in neurobehavioral dysfunction were related to the degree of past solvent exposure. There was little risk of organic brain damage in workers with fewer than 13 years of exposure to the equivalent of a time-weighted average of 40 ppm of white spirit. [Mixed solvent exposure and organic brain damage. A study of painters. Acta Neurol Scand Suppl 1988;118:1-143] A workshop of the World Health Organization described three effects from chronic exposure to organic solvents: 1) organic affective syndrome (reversible irritability, fatigue and difficulty concentrating); 2) mild chronic toxic encephalopathy (sustained mood changes and impairment of intellectual function); and 3) severe chronic toxic encephalopathy (irreversible dementia characterized by deterioration of memory and cognitive function). [Levy, p. 438] This syndrome was first diagnosed in Swedish clinics in the 1970s among painters and boatbuilders (styrene), but it is rarely seen now. [Wegman DH, Hogstedt C. Status Report on Swedish work environment research--history, context and international evaluation. Scand J Work Environ Health 2007, vol 33, suppl 1, p. 12] There were 129 cases of occupational chronic solvent encephalopathy (CSE) diagnosed in Finland from 1995-2007. Annual incidence has decreased from 18 to 3 cases per year. Water-soluble paints and lacquers are now used in over 70% of construction painting, but only 10% of industrial painting. At greatest risk for CSE are workers over the age of 45 who spray painted with aromatic hydrocarbons for greater than 20 years. Of the 129 patients, 118 had begun working in the 1960s and 1970s when solvent exposure was more extensive. [PMID 19941001
] Solvent-based paints (SBP) are still widely used in steel bridge and storage tank maintenance. "One major finding was that the solvent air concentrations were approximately 3-fold higher before 1990 than after. . . . There are three major factors contributing to the calculated lifetime solvent exposure index: (1) number of years using SBP, (2) proportion of time spent spraying compared with other application methods, and (3) level of protection used." [PMID 21660830
] "Concentrations of solvents in paints have steadily declined during the working lifetime of subjects in this study. Although reduced performances was observed on individual tests, these alterations were not consistent across tests and unlikely to be of clinical significance." [PMID 30308619
] See "Chronic solvent-induced encephalopathy: course and prognostic factors of neuropsychological functioning." [PMID 29943196
] The most hazardous solvents are volatile at room temperature. They are or were commonly used in open processes such as degreasing metals and thinning paints. They are not obnoxious in smell or irritating effects--workers could tolerate high concentrations on a daily basis. See the Process, "Painting (Solvents)."