Urban mosquitoes and filamentous green algae: their biomonitoring role in heavy metal pollution in open drainage channels in Nairobi industrial area, Kenya.

BACKGROUND: Industrial wastewater is a human health hazard upon exposure. Aquatic organisms in contaminated wastewater may accumulate the toxic elements with time. Human population living in informal settlements in Nairobi industrial area risk exposure to such toxic elements. Biomonitoring using aquatic organisms in open drainage channels can be key in metal exposure assessment. Levels of Mercury (Hg), Lead (Pb), Chromium (Cr), Cadmium (Cd), Thallium (Tl), and Nickel (Ni) were established in samples of wastewater, filamentous green algae (Spirogyra) and mosquitoes obtained from open drainage channels in Nairobi industrial area, Kenya. RESULTS: Pb, Cr, & Ni levels ranged from 3.08 to 15.31 µg/l while Tl, Hg, & Cd ranged from 0.05 to 0.12 µg/l in wastewater. The Pb, Cr, Ni, & Cd levels were above WHO, Kenya & US EPA limits for wastewater but Hg was not. Pb, Cr, Tl, & Ni levels in assorted field mosquitoes were 1.3-2.4 times higher than in assorted laboratory-reared mosquitoes. Hg & Cd concentrations in laboratory-reared mosquitoes (0.26 mg/kg & 1.8 mg/kg respectively) were higher than in field mosquitoes (0.048 mg/kg & 0.12 mg/kg respectively). The levels of Pb, Cr, & Ni were distinctively higher in field mosquito samples than in wastewater samples from the same site. Pb, Cr, Ni, Cd & Hg levels in green filamentous Spirogyra algae were 110.62, 29.75, 14.45, 0.44, & 0.057 mg/kg respectively. Correlation for Pb & Hg (r (2) = 0.957; P < 0.05); Cd & Cr (r (2) = 0.985; P < 0.05) in algae samples was noted. The metal concentrations in the samples analyzed were highest in filamentous green algae and least in wastewater. CONCLUSION: Wastewater, mosquitoes, and filamentous green algae from open drainage channels and immediate vicinity, in Nairobi industrial area (Kenya) contained Hg, Pb, Cr, Cd, Tl, and Ni. Mosquitoes in urban areas and filamentous green algae in open drainage channels can play a role of metal biomonitoring in wastewater. The potential of urban mosquitoes transferring heavy metals to human population from the contaminated wastewater should be investigated.

Lifestyles and practices that enhance malaria and typhoid fever in Njoro District, Kenya.

Unhygienic practices have been associated with the spread of parasitic and bacterial infections in rural areas. This study was designed to verify the link between the frequencies of malaria and typhoid fever with selected rural practices in Njoro District, Kenya. A cross-sectional study involving observations, questionnaires and interviews was conducted to determine the socio-economic variables and practices/lifestyles in 336 randomly selected homesteads. Frequencies of malaria and typhoid fever in two randomly selected health centers were determined through a retrospective study for the period from 2004 to 2009. The respondents had large families (68%), low education level (67%) and high responsibility burden (67%). Individuals who did not boil drinking water constituted 61%. Boiling drinking water was less common among the poor, Odds Ratio (OR) of 2.36, χ(2) = 9.88, 95% Confidence Interval (CI) of 1.38-4.03. Respondents who washed their hands in a basin after using the latrines comprised 79.8% while 4.8% did not. 18.5% of the respondents did not use a soap to wash their hands after using the latrine. One third (33.6%) of the homesteads had dirty and inappropriate pit latrines while 2.7% of the homesteads lacked latrines. Failure to use mosquito bed nets was more likely to occur among the poor respondents, OR of 1.44, χ(2) = 1.74, 95% CI of 0.84-2.48. The frequencies of malaria and typhoid fever were an average of 29 and 24% respectively. Malaria and typhoid fever cases were relatively frequent due to adoption of inappropriate lifestyles and practices that predisposed the residents to infectious agents. Poverty seemed to play a significant role in the spread of malaria and typhoid fever.