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Biomedical subjects

K L Purvis

Publications and source records attributed to K L Purvis.

4 recordsLinked to original sources

Worker exposure and health risks from volatile organic compounds utilized in the paint manufacturing industry of Kenya.

This study provides a means for the evaluation of cleaner manufacturing and the provision of cost-effective worker health improvements in developing nations. Individual worker exposure to volatile organic compounds was measured in the paint manufacturing plants of Nairobi, Kenya. A variety of different paint production jobs were monitored, including laboratory researchers, mixers, tinters, fillers, cleaners, raw materials deliverers, and resins producers. Exposure levels were calculated based on a time-weighted average over an entire 8-10 hour workday. The paint solvents used can cause both acute and chronic health problems for the workers exposed. For example, over half of the organics monitored, i.e. benzene, styrene, and xylene, exhibit carcinogenic properties. The lifetime cancer risk from exposure to these paint solvents was estimated utilizing published cancer potencies, and the risks range from 1.90 x 10(-4) for raw materials deliverers to 2.60 x 10-2 for cleaners. The highest exposure tasks included cleaning the mixing vats and mixing the paint product, ranging from risks of 8.5 x 10(-4) to 2.6 x 10(-2), providing evidence that solvent exposure occurs due to point sources. Because of this, simple and inexpensive technologies should significantly reduce the excess exposure of workers in these manufacturing facilities. The cost of minor-innovations in the plants themselves, such as fans, drum and mixing vat covers, and respirators, could amount to as much as five times less than the estimated cost of treating workers who develop cancer due to paint solvent exposure.

Cost-Benefit Analysis↗

Phonological processing, not inhibitory control, differentiates ADHD and reading disability.

OBJECTIVE: To test for the distinctiveness of attention-deficit hyperactivity disorder (ADHD) and reading disability (RD) and the independence of the cognitive domains, inhibition and phonological processing, which are proposed as central to ADHD and RD, respectively, using a classic double dissociation design. METHOD: A 2 (ADHD versus no ADHD) x 2 (RD versus no RD) model was used to examine the cognitive profile of 4 groups of children, aged 7 to 11 years. Two measures of inhibitory control and 3 phonological processing measures were used. RESULTS: The 2 RD groups (RD, ADHD + RD) were significantly impaired relative to the 2 non-RD groups (controls, ADHD) on all phonological processing measures. The 2 ADHD groups were significantly impaired on simple go-task responding relative to the non-ADHD groups and in inhibition. Contrary to predictions, an RD effect on inhibitory control was found on one inhibition measure. The comorbid group (ADHD + RD) generally exhibited the deficits of both single groups in an additive fashion. CONCLUSIONS: These findings question the role of inhibitory control as a unique cognitive marker for ADHD and suggest true comorbidity for children with both ADHD and RD.

Attention Deficit Disorder with Hyperactivity↗

Language abilities in children with attention deficit hyperactivity disorder, reading disabilities, and normal controls.

Research has demonstrated a high prevalence of language impairments (LI) and reading disabilities (RD) in children with attention deficit hyperactivity disorder (ADHD). Since RD is also associated with LI, it is unclear whether the language impairments are specific to ADHD or associated with comorbid RD. The language abilities of ADHD children with and without RD were investigated in a task requiring recall of a lengthy narrative, and in tests assessing knowledge of the semantic aspects of language. The study was conducted with 50 boys--14 ADHD, 14 ADHD + RD, 8 RD, and 14 normal controls, aged 7 to 11. Children with ADHD (ADHD-only, ADHD + RD) exhibited difficulties in organizing and monitoring their story retelling. Children with RD (RD-only, ADHD + RD) demonstrated deficits in receptive and expressive semantic language abilities on the language processing tests. The comorbid group (ADHD + RD) exhibited the deficits of both ADHD and RD children. The deficiencies of ADHD children are consistent with higher-order executive function deficits while the deficits of RD children are consistent with deficits in the basic semantics of language processing.

Achievement↗

Narrative abilities in children with attention deficit hyperactivity disorder and normal peers.

A story retelling task was used to assess narrative abilities in 30 boys with attention deficit hyperactivity disorder (ADHD) and 30 normally developing boys, matched on age and IQ. Each boy listened to two stories and retold them for another child. Results indicated that the two groups did not differ in their ability to comprehend and extract the main ideas from the stories, but did differ in the production of narratives. Boys with ADHD provided less information overall, and their stories were more poorly organized and less cohesive and contained more inaccuracies. As a result, their stories were often confused and hard to follow. Organization and monitoring of information are functions of executive control. Thus the observed deficits in narrative production in children with ADHD may reflect underlying deficits in executive processes.

Attention Deficit Disorder with Hyperactivity↗