Speaking generally, when chemical exposures cause medical sequelae, the duration of the claimed exposure is a factor (along with the quantitative extent of exposure and route of absorption) that may be determinative of whether a causal link exists. That is, the shorter duration the exposure, the less likely there is a causal link. A prolonged exposure is generally measured in years, such as with smoking. Brief exposures do not cause rheumatoid arthritis or osteoarthritis. Moreover, exposure to unidentified contaminants, whether brief or not—cannot cause a rheumatoid factor to become positive and, therefore, cannot cause it to become positive within only a few weeks.
Chemical exposures and rheumatologic diagnoses medical expert witness specialties include rheumatology and toxicology.