Influence of ergonomic factors on peripheral neuropathy under HAV exposure.

BACKGROUND: Hand-arm vibration (HAV) is a risk factor for carpal tunnel syndrome (CTS) and ulnar neuropathy at the elbow (UNE). It is unclear how ergonomic factors influence the relationship between HAV exposure and CTS and UNE. AIMS: We aimed to assess the relationship between cumulative HAV exposure and CTS and UNE in workers exposed to HAV from two tools with different ergonomic profiles. METHODS: We performed nerve conduction studies (NCSs) of the sensory and motor median and ulnar nerves and recorded symptoms indicating CTS and UNE in workers exposed to HAV from impact wrenches or from rock drills. Exposure was measured as cumulative lifetime exposure. We used linear regression adjusted for age and body mass index to assess linear relationships. RESULTS: Sixty-five workers participated (33 rock drill and 32 impact wrench operators). We found inverse linear associations between cumulative HAV exposure and median nerve sensory conduction velocity in impact wrench operators and ulnar nerve motor conduction velocity in rock drill operators (beta of 0.63 and 0.75). Based on NCS findings and symptoms, seven impact wrench operators had CTS and one UNE, and four rock drill operators had CTS and six UNE. CONCLUSIONS: Our findings indicate that ergonomic factors influence the development of CTS and UNE under HAV exposure. The ergonomic profile seems to influence which type of neuropathy workers exposed to HAV will develop. Design of occupational exposure guidelines and future studies should be based on ergonomic profile and exposure characteristics for different tools and not merely HAV.

Selenium and mercury in Brazilian Cerrado soils and their relationships with physical and chemical soil characteristics.

The objective of this study was to determine the natural concentrations of Hg and Se in 45 representative soil profiles from the Cerrado biome in central Brazil, and to correlate their concentrations with soil chemical and physical characteristics. The study area was composed of three sub-regions: Goiás, Northwest of Minas Gerais, and Minas Gerais Triangle. Selenium and Hg concentrations were determined by acid digestion and atomic absorption spectroscopy. Data were subjected to analysis of variance on the means of the Hg and Se variables within each soil class at two depths, followed by multivariate statistical methods. The Hg concentrations ranged from 15 to 182 µg kg-1 and the Se concentrations ranged from 22 to 72 µg kg-1. The soil characteristics that most contributed to Hg concentrations in the soils, according to principal component analysis, were Fe2O3, FeO, TiO2, pH, P2O5, and effective CEC. In general, the soils of the Cerrado biome have deficient Se concentrations. The Humic Rhodic Acrustoxes have Hg concentrations above the prevention reference value for soils of Minas Gerais.

Phosphate-binding capacity of ferrihydrite versus calcium acetate in rats.

Calcium salts, such as calcium carbonate and calcium acetate, are the principal compounds used as phosphate binders in patients with chronic renal failure. The dose required is three to six times the normal requirement for calcium. Use of these large doses of calcium salts in the diet can result in hypercalcemia. Other compounds have been investigated as phosphate binders with varying degrees of success. Synthetic ferrihydrite (5Fe(2)O(3).9H(2)O) has a high adsorptive capacity for phosphate and may be an effective phosphate binder. The phosphate-binding capacity of ferrihydrite was compared with that of calcium acetate in 250-g male Sprague Dawley rats. After an overnight fast, rats (n = 5 per group) were gavaged with an American Institute of Nutrition (AIN) 76 formula containing one third the daily phosphorus intake labeled with phosphorus-32 ((32)P). Either two levels of calcium acetate, representing three (1/2X) or six (1X) times the usual calcium intake for one third of the day, or equivalent amounts of ferrihydrite were added to the diet. An additional group received two times (2X) the larger dose, and a sixth control group received no binder in the diet. Phosphorus absorption curves were determined from (32)P appearance in the serum. The 1/2X dose of ferrihydrite reduced (32)P by approximately one half, and the 2X dose nearly completely suppressed (32)P absorption, similar to the 1X dose of calcium acetate. The advantage of using a ferrihydrite binder would be to avoid the hypercalcemia resulting from the use of high-dose calcium salts. An added advantage may result from the small amounts of iron absorbed in these chronically iron-deficient patients.

Effect of sorbitol on the phosphate adsorptive capacity of ferrihydrite suspensions.

The purpose of this study was to stabilize the phosphate adsorptive capacity of aqueous suspensions of ferrihydrite, a potential phosphate binder. Ferrihydrite was precipitated by the addition of 1 N NaOH to 1 M FeCl3 until pH 8.0 was reached. The ferrihydrite suspension was divided into three portions and an amount of sorbitol was added to produce sorbitol concentrations of 0, 1, or 5% w/v, respectively. The phosphate adsorptive capacity and X-ray diffraction pattern were periodically determined during aging at room temperature. The phosphate adsorptive capacity of the ferrihydrite suspension containing 0% sorbitol decreased steadily from 0.012 mgP/mg to 0.007 mgP/mg during the 1-year aging period. In contrast, suspensions containing 1 or 5% sorbitol exhibited constant phosphate adsorptive capacities during this period. X-ray diffraction patterns revealed that ferrihydrite transformed to hematite and goethite during aging of the control suspension. The presence of 1 or 5% sorbitol prevented the transformation of ferrihydrite to more crystalline iron oxides. This study suggests that the phosphate adsorptive capacity of ferrihydrite suspensions can be stabilized by the incorporation of small amounts of sorbitol into the formulation.