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Biomedical subjects

C S Clark

Publications and source records attributed to C S Clark.

At least 19 recordsLinked to original sources
PubMed2006

The lead content of currently available new residential paint in several Asian countries.

Worldwide prohibitions on lead gasoline additives were a major international public health accomplishment, the results of which are still being documented in parts of the world. Although the need to remove lead from paints has been recognized for over a century, evidence reported in this article indicates that lead-based paints for household use, some containing more than 10% lead, are readily available for purchase in some of the largest countries in the world. Sixty-six percent of new paint samples from China, India, and Malaysia were found to contain 5000 ppm (0.5%) or more of lead, the US definition of lead-based paint in existing housing, and 78% contained 600 ppm (0.06%) or more, the limit for new paints. In contrast, the comparable levels in a nearby developed country, Singapore, were 0% and 9%. In examining lead levels in paints of the same brands purchased in different countries, it was found that some brands had lead-based paints in one of the countries and paints meeting US limits in another; another had lead-free paint available in all countries where samples were obtained. Lead-based paints have already poisoned millions of children and likely will cause similar damage in the future as paint use increases as countries in Asia and elsewhere continue their rapid development. The ready availability of lead-based paints documented in this article provides stark evidence of the urgent need for efforts to accomplish an effective worldwide ban on the use of lead in paint.

China↗
PubMed2005

Lead in paint and soil in Karnataka and Gujarat, India.

Blood lead surveys in several areas of India have found very high percentages of children with elevated blood lead levels. Fifty-three percent of children under 12 years of age in a seven-city screening had blood lead levels equal to or greater than 10 microg/dL, the level currently considered elevated by the U.S. Centers for Disease Control and Prevention (CDC). A number of these surveys focused on populations near lead smelters or in areas with high lead levels from combustion of lead-containing gasoline. There is little information available, however, on the levels of lead in paint in India and in soil. Field portable X-ray fluorescence analyzers were used to determine environmental lead levels in paint, dust, air, soil, and other bulk samples near several lead-using industries and in the residential environments of children with very high blood lead levels, at least four times as high as the CDC limit. Soils near industrial operations, such as secondary lead smelters, and battery dismantling units contained levels up to 100,000 ppm of lead. Four of 29 currently available paints from five manufacturers measured 1.0 mg/cm2 or above--the current U.S. definition of lead-based paint in housing-after the application of a single coat; four others measured at least 1.0 after three coats, and three others likely reached this level after the application of an additional one or two coats. In 5 of 10 homes of the elevated blood lead children, three or more locations in or around the home were found to have lead paint levels of 1.0 mg/cm2 or higher. Soil exceeding the U.S. standard for residential areas (400 ppm) was found at only one of the houses. Other sources of lead exposure, including traditional ayurvedic medicine tablets, were also observed. Similar surveys would be useful elsewhere in India and in other developing countries.

Data Collection↗
PubMed2004

Portable lead analyzer to locate source of lead.

OBJECTIVE: To investigate the sources of lead in the environment in children with elevated blood, with the help of a Field Portable X-Ray Fluorescence Analyzer. METHODS: One hundred and seven school children were chosen for this study on a random basis, from Mangalore and Karnataka. Their blood lead was analyzed. Of the cases analyzed, 10 students whose blood lead level was more than 40 microg/dl were investigated using a field portable X-Ray Fluorescence Analyzer. This is the first time such a device has been available for this purpose in India. RESULTS: The 'likely' source of lead exposure could be determined in eight cases which was from the immediate environment of the children like 'lead-based' paint on surfaces in the house, on playground and other exterior equipment; lead storage batteries, contaminated dust and soil and other lead-containing substances. CONCLUSION: The use of an X-Ray Fluorescence Analyser appeared to be useful in determining the source of lead.

Child↗
PubMed1999

Evaluation of a portable X-ray fluorescence instrument for the determination of lead in workplace air samples.

Occupational Safety and Health Administration (OSHA) regulations for worker exposure to lead specify worker protection levels based upon airborne concentrations of lead dust. The rapid, on-site determination of lead in air filter samples using a portable x-ray fluorescence (XRF) instrument with an attachment to hold the filter would expedite the exposure assessment process and facilitate compliance with the OSHA standards. A total of 65 lead in air filter samples were collected at bridge blasting lead-abatement projects using closed-faced, 37-mm cassettes with pre-loaded 0.8 micron pore size mixed cellulose ester membrane filters. The lead loading range of the data set was 0.1-1514.6 micrograms (micrograms) of lead/sample. Samples were initially analyzed with a field portable XRF (NITON 700) using an experimental non-destructive XRF method. Samples were subsequently analyzed using National Institute for Occupational Safety and Health (NIOSH) Method 7105 (Graphite Furnace AA) as a reference analytical method. The paired data were not normally distributed; therefore, the non-parametric Wilcoxon signed rank test was used for statistical analysis. There was no statistically significant difference between data from the field portable XRF method and the NIOSH method (p-value = 0.72). Linear regression of the data resulted in a slope of 0.959, a y-intercept of 5.20 micrograms, and an r2 of 0.985. The XRF limit of detection and limit of quantitation were determined to be 6.2 and 17 micrograms of lead/sample, respectively. The XRF method accuracy was +/- 16.4% (7.1%-27%, 90% confidence interval). The data presented in this study indicate that field-portable XRF can be used for the analysis of lead air filter samples over the range of 17 to 1500 micrograms of lead/sample. The practicing industrial hygienist can use field-portable XRF to produce a rapid, on-site determination of lead exposure that can immediately be communicated to workers and help identify appropriate levels of personal protection. As the method is non-destructive, samples can subsequently be sent to a laboratory for confirmation. Confirmation would be recommended when greater than 16.4 percent accuracy from an analytical method is required. This study provided data of suitable quality for the development of NIOSH Method 7702, "Lead by Field Portable XRF."

Air Pollutants, Occupational↗
PubMed1997

Dispelling managed care myths.

A number of ideas regarding managed care and capitation are commonly accepted as truths. In reality, however, these ideas are half-truths or myths. Healthcare providers need to challenge some of these myths in order to respond proactively to change. Some of the traditional thinking about managed care that needs realignment includes the belief that PHOs essentially are transitional vehicles and not viable, long-term solutions; that the incentives under fee-for-service payment conflict totally with the incentives under capitation; that under global capitation, the best method for paying primary care physicians is capitation and the best way to pay specialists is discounted fee-for-service; and that small, exclusive physician panels are the most successful for managed care.

Capitation Fee↗
PubMed1995

Accentuation of gas exchange gradients in flushes of ponderosa pine exposed to ozone.

Two-year-old ponderosa pine seedlings (Pinus ponderosa Laws.) were exposed to episodic O(3) concentrations in open-top chambers for two consecutive growing seasons (June through September of 1990 and 1991). Near the end of the second season of O(3) exposure, gas exchange was measured on needles of surviving flushes at saturating CO(2) and photosynthetic photon flux density (PPFD). Both photosynthetic capacity (A(sat)) and stomatal conductance to water vapor (g(wv)) declined linearly with needle age but differences within a flush were also found. Gas exchange rates of needles from the base of the current-year flush were significantly lower than those of needles from the top of the flush, even though age differences between needles were negligible. Although most measurements were conducted at saturating CO(2), similar patterns of gas exchange were also found at 350 micro mol mol(-1) CO(2), indicating that photosynthesis of needles at the bottom of the flush was more strongly affected by O(3) than that of needles at the top of the flush, even though the potential for O(3) uptake was probably less in needles at the bottom of the flush because of reduced stomatal conductance. Carboxylation efficiency (deltaA/deltaC(i)), the linear slope of the A/C(i) response, was highly correlated with A(sat), varying with needle age, needle position in the flush and O(3) exposure, but the magnitude of the reductions was greater than for A(sat). We conclude that susceptibility to O(3) damage among needles of an individual seedling varies not only with needle age but also with needle position, and that reductions in photosynthetic capacity may not be directly attributable to increased uptake of the pollutant. The data also indicate the need to consider within-flush variation when estimating whole-plant carbon gain and O(3) uptake.

Journal Article↗
PubMed1994

Managed care innovation and new product development.

This article explores recent innovative activity by managed care payor plans nationwide with particular emphasis on emerging, new relationships between the plans and their purchasers, enrollees, provider panels, and competitors. Because they already practice what advocates of health care reform are now preaching, many managed care plans are leading the charge to transform our health care delivery and financing systems.

Administrative Personnel↗
PubMed1994

Proportional mortality analysis of wastewater treatment system workers by birthplace with comments on amyotrophic lateral sclerosis.

There is concern that wastewater treatment system workers are at risk for cancers and diseases affecting the neurological and digestive systems. However, these diseases have also been linked to early exposures. A proportional mortality study was conducted on a large cohort of wastewater treatment system workers who were divided into two groups, migrants and nonmigrants, by place of birth as reported on their death certificates. The migrant worker group was significantly higher than the US white male population for cancer of the stomach, leukemia, and all lymphopoietic cancers. Migrant workers also had an elevated ratio for all diseases of the nervous system and sense organs. No cases of amyotrophic lateral sclerosis were found. The American-born workers had an elevated rate of death for arteriosclerotic heart disease compared with the US white male population. We suggest that place of birth may present a confounding factor when evaluating exposures in employee groups.

Aged↗
PubMed1993

Analysis of the relationships among O(3) uptake, conductance, and photosynthesis in needles of Pinus ponderosa.

We studied the effects of O(3) uptake on conductance (g(wv)) and photosynthesis (A) in needles of ponderosa pine (Pinus ponderosa Laws.) seedlings exposed for 70 days to one of three O(3) regimes-Low-O(3) (0.1 micro mol mol(-1) daily peak), High-O(3) (0.2 micro mol mol(-1) daily peak), and Low/High-O(3) (alternating 2 days Low-O(3) and 2 days High-O(3)). Seedlings exposed to charcoal-filtered air served as controls. Total O(3) exposures, expressed as ppm-h (the sum of the average hourly concentration in ppm ( micro mol mol(-1)) over the exposure period), were 77, 135, 105 and 4 for the Low-O(3), High-O(3), Low/High-O(3) and control treatments, respectively. Conductance (g(wv)) declined to about 60% of the value in control seedlings by Day 6 in seedlings in the High-O(3) treatment and by Day 37 in seedlings in the Low/High-O(3) treatment, but g(wv) did not decline at all in seedlings in the Low-O(3) treatment. At the end of the 70-day experiment, cumulative O(3) uptake, calculated from measured g(wv) values and assuming an internal O(3) concentration of zero, was 12.2, 13.5, and 14.7 mmol m(-2) for seedlings in the Low-O(3), Low/High-O(3), and High-O(3) treatments, respectively; however, O(3) uptake was reduced by 0, 24, and 36%, respectively, from that expected if there had been no decline in g(wv). With increasing total O(3) exposure, A declined, but the reduction was not strictly cumulative, i.e., A measured on Days 49 and 70 was similar for a given treatment even though both total O(3) exposure and uptake had increased. At the end of the experiment, A at near saturating CO(2) (1000 micro mol mol(-1)) and saturating photosynthetic photon flux density was reduced by about 25, 40 and 50% in seedlings in the Low-O(3), Low/High-O(3) and High-O(3) treatments, respectively, compared to the control seedlings. The ratio of internal to external CO(2) concentrations, an indicator of relative change in stomatal limitation of A, did not change over time and did not differ among treatments, suggesting that A and g(wv) decreased in parallel. After 40-60 days without O(3), A of seedlings in all O(3) treatments was not significantly different. Our data indicate that O(3)-induced stomatal closure was a result of reduced A and that decreased g(wv) reduced O(3) uptake to a rate that needles of ponderosa pine could tolerate without exhibiting further reductions in gas exchange capacity.

Journal Article↗
PubMed1988

Animal viruses, coliphages, and bacteria in aerosols and wastewater at a spray irrigation site.

Aerosol samples collected at the Muskegon County Wastewater Management System Number 1 spray irrigation site in Michigan by using the Army prototype XM2 Biological Sampler/Collector were examined for the presence of animal viruses, coliphages, and bacteria. Air samples, collected in Earle lactalbumen hydrolysate, and wastewater samples were filtered through a 0.45- and 1.2-micron membrane filter sandwich, pretreated with 10% beef extract (pH 7.0), and assayed for animal viruses by the plaque method on Buffalo green monkey kidney cells. Untreated air and wastewater samples were assayed for coliphages by the soft agar overlay method with three Escherichia coli hosts (ATCC 13706, 15597, and 11303) and for bacteria by the heterotrophic plate count method. Filtered air samples were assayed for coliphages by the most-probable-number method with the same three hosts. Although no animal viruses were detected in the aerosol samples, coliphages and bacteria were recovered. E. coli ATCC 13706 coliphage were recovered more often and in greater numbers than either of the other two types of coliphages. Concentrations of animal viruses, coliphages, and bacteria detected in the raw influent decreased as the wastewater was aerated and stored in the lagoons. No animal viruses were detected in the wastewater at the pump station just before distribution to the spray irrigation rigs. The most-probable-number method was more sensitive and consistent than the overlay procedure in detecting low levels of coliphages in air samples.

Aerosols↗
PubMed1988

Dare to downsize.

Explore the source record for details and available documents.

Efficiency↗