Environmental exposure to manganese in air: Tremor, motor and cognitive symptom profiles.

BACKGROUND: Excessive exposure to manganese (Mn) may cause parkinsonian-like motor and tremor symptoms and adverse cognitive effects, including problems with executive functioning (EF), resembling those found in later-stage Parkinson's disease (PD). Studies seeking to differentiate PD patients into subgroups with associated cognitive and functional outcomes using motor and tremor symptoms identified tremor-dominant (TD) and non-tremor dominant (NTD) subtypes. It is unclear whether differing patterns of pathophysiology and symptoms exist in Mn neurotoxicity, as they do in PD. METHODS: Residents of East Liverpool (n=83) and Marietta, OH (n=99) exposed to chronic (>10years) environmental Mn through industrial pollution were administered neuropsychological measures and a physician-rated scale of movement-disorder symptoms. Two-step cluster analysis was used to group residents based on tremor symptoms, bradykinesia/rigidity symptoms, gait disturbance, and executive function. Cluster membership was validated using modeled air-Mn exposure and a computerized tremor measure. RESULTS: Elevated tremor and motor symptoms and executive dysfunction were observed, and TD and NTD symptom clusters were identified. Two additional clusters were also identified: Executive Dysfunction and Normal Functioning. The NTD residents, with elevated levels of gait disturbance and other movement disorder symptoms, did not evidence EF impairment, as predicted. Instead, residents with EF impairment formed their own cluster, and were relatively free of movement disorder symptoms. CONCLUSIONS: Results resemble reports in the PD literature with TD and NTD clusters identified, but executive dysfunction did not cluster with NTD symptoms. PD and Mn exposure likely have differing pathophysiology and developmental courses, and therefore different symptom patterns, even when similar symptoms are present.

Effective dose equivalent due to gamma-ray emissions from hot particles.

The quantification of dose from hot particles in the nuclear power industry has received a good deal of attention in the past few years. Specifically, calculational models have been developed to determine shallow dose equivalent from both beta and gamma-rays (using VARSKIN) and to estimate deep dose equivalent based upon the gamma dose at a tissue depth of 1 cm. These two values are reported for regulatory purposes. The purpose of this study is to estimate another measure of dose from hot particles (or from skin contamination over a small area), specifically the effective dose equivalent which takes into account all organs of the body receiving appreciable dose from the gamma-ray emissions from the contamination. While it is generally recognized that this dose will be small, this study gives representative doses for a range of hot particle locations and gamma-ray energies. MCNP and the ADAM phantom have been used for the calculational model. The effective dose equivalent is found to range from 0.1 to 12 microSv h(-1) MBq(-1) (0.4 to 43 microrems h(-1) microCi(-1)) of gamma activity, depending upon the location of the hot particle on the body.