Phytoremediation Using Bamboo to Reduce the Risk of Chromium Exposure from a Contaminated Tannery Site in Kenya.

BACKGROUND: This study examines an intervention strategy to reduce the risk of chromium (Cr) exposure. It follows a previous Cr exposure investigation, which revealed that large volumes of Cr-contaminated waste were burnt on site. The study site had a long history of land-based waste disposal since 1994. OBJECTIVE: The potential for phytoremediation using bamboo species to restore Cr-contaminated soil was evaluated. METHODS: Chromium levels and physico-chemical properties of the tannery and control soils were analyzed before transplanting six different bamboo species. Translocation, bio-concentration and bioaccumulation factors of the species were assessed for phytoremediation capabilities. RESULTS: Chromium levels in the tannery soils ranged from 1337.0 to 3398.0 mg/kg dw. The chromium levels were significantly higher (P < 0.05) than those of the control soils (0.20 to 2.34 mg/kg dw) and markedly exceeded the recommended limit of 100 mg/kg dw. The physicochemical properties of the tannery soils were also significantly varied (P < 0.05) compared to the control soils. In all cases, the species grown in the tannery soils were tolerant to a wide range of prevailing conditions. All of the bamboo species in the present study had a 100% survival rate in the tannery soils, except for D. birmanicus, which had a survival rate of 83.3%. Moreover, growth performance of the species in the tannery and control soils as evaluated by height and clump diameters did not vary significantly (P > 0.05). However, Cr levels in the tannery differed significantly (P < 0.05) among the species and rhizosphere soils. D. asper, B. vulgaris, D. membranaceus and B. blumeana had a bio-concentration factor (BCF) > 1 and translocation factor (TF) < 1, indicating that they are suitable for phytostablization. On the contrary, B. bambos had a bioaccumulation factor (BAF) < 1 and TF > 1, indicating potential for phytoextraction, while D. birmanicus showed no potential for phytoextraction or phytostabilization. CONCLUSIONS: The present study identified D. asper, B. vulgaris, D. membranaceus and B. blumeana as suitable for restoration of Cr-contaminated tannery sites. Close monitoring of toxic metals is necessary during application of these species. Further studies are also recommended using a wide variety of bamboo species to optimize their application in phytoremediation.

Lead exposure and blood pressure among workers in diverse industrial plants in Kenya.

The study evaluated airborne exposures and blood lead (BPb) levels in 233 production workers at six diverse industrial plants in Kenya. Blood and personal breathing zone air samples were collected and analyzed for lead (Pb) using atomic absorption spectroscopy. Blood pressure (BP) levels were measured using a standard mercury sphygmomanometer. The results indicated mean airborne Pb levels ± standard deviation (SD) as follows: 183.2 ± 53.6 µg/m(3) in battery recycling, 133.5 ± 39.6 µg/m(3) in battery manufacturing, 126.2 ± 39.9 µg/m(3) in scrap metal welding, 76.3 ± 33.2 µg/m(3) in paint manufacturing, 27.3 ± 12.1 µg/m(3) in a leather manufacturing, and 5.5 ± 3.6 µg/m(3) in a pharmaceutical plant. The mean airborne Pb levels exceeded the U.S. Occupational Safety and Health Administration (OSHA) 8-hr time-weighted average (TWA) permissible exposure limit (PEL) for Pb of 50 µg/m(3) in the battery manufacturing, battery recycling, welding, and paint manufacturing plants. Similarly, mean BPb concentrations exceeded the American Conference of Governmental Industrial Hygienists (ACGIH®) biological exposure index (BEI) for Pb of 30 µg/dl. A significant positive association was observed between BPb and breathing zone air Pb (R(2) = 0.73, P < 0.001). Approximately 30% of the production workers (N = 233) were in the hypertensive range with an average systolic and diastolic blood pressure (BP) of 134.7 ± 12.7 mmHg and 86.4 ± 8.9 mmHg, respectively. In the multivariate regression analysis, age, duration of work, airborne Pb and BPb levels were significantly associated (P < 0.05) with a change in BP. We recommend improved engineering controls, work practices, and personal hygiene to reduce Pb exposures. In addition, workers should undergo comprehensive medical surveillance to include BPb and BP testing, and airborne Pb assessments in all industries with significant lead exposures.

Air and blood lead levels in lead acid battery recycling and manufacturing plants in Kenya.

The concentration of airborne and blood lead (Pb) was assessed in a Pb acid battery recycling plant and in a Pb acid battery manufacturing plant in Kenya. In the recycling plant, full-shift area samples taken across 5 days in several production sections showed a mean value ± standard deviation (SD) of 427 ± 124 µg/m(3), while area samples in the office area had a mean ± SD of 59.2 ± 22.7 µg/m(3). In the battery manufacturing plant, full-shift area samples taken across 5 days in several production areas showed a mean value ± SD of 349 ± 107 µg/m(3), while area samples in the office area had a mean ± SD of 55.2 ± 33.2 µg/m(3). All these mean values exceed the U.S. Occupational Safety and Health Administration's permissible exposure limit of 50 µg/m(3) as an 8-hr time-weighted average. In the battery recycling plant, production workers had a mean blood Pb level ± SD of 62.2 ± 12.7 µg/dL, and office workers had a mean blood Pb level ± SD of 43.4 ± 6.6 µg/dL. In the battery manufacturing plant, production workers had a mean blood Pb level ± SD of 59.5 ± 10.1 µg/dL, and office workers had a mean blood Pb level ± SD of 41.6 ± 7.4 µg/dL. All the measured blood Pb levels exceeded 30 µg/dL, which is the maximum blood Pb level recommended by the ACGIH(®). Observations made in these facilities revealed numerous sources of Pb exposure due to inadequacies in engineering controls, work practices, respirator use, and personal hygiene.