Quantitative modelling of Ostracod bioassay: assigning toxicity index to potentially chemical contaminated swimming pools.

One of the primary objectives of any public health programme is to design a protocol that will curtail a population from being predisposed to toxic substances in the environment. Biomarkers help in actualising such an objective by their potential to detect the presence of toxic substances in environmental media such as soil, water and air. The Ostracod Heterocypris incongruens, an already established biomarker for quality evaluation of freshwater, does not quantify toxicity. This work was aimed at modelling Ostracod bioassay as a quantitative whole-water toxicity assay (QWTA) for the determination of potentially chemical contaminated swimming pools. In this modelling approach, a pool water sample was deliberately contaminated with a mixture of Fenton reagent (FR) and Bonny light (BL) crude oil. The mechanism of toxic injury of this mixture is via oxidative stress-mediated superoxide ion and other free radicals. The mortalities and growth factors of the exposed freshly hatched Ostracods to the serial dilutions of the contaminated swimming pool water sample for 6 days were mathematically modelled to toxicity indices (Ti), which were used to construct the toxicity reference curve (TRC). A graph of the "toxic concentrations" of the serially diluted contaminated pool water sample against Ostracod mortality was plotted. The TRC and the linear graph constitute the "Ostracod-linked mathematical model". Against the reference mortality ≤ 20% of the Ostracods, the toxicity index based on the model prediction is ≤ 32.5, and this signifies "no observed toxic effect" for toxicity values below 32.5 units. Using this model, toxicity indices were calculated for 5 randomly selected swimming pools in the study area. The results showed that the outdoor pool SP 5 has a toxic index of 49.0, while outdoor pools SP 2 and SP 3 each has a toxic index of 42.5. The indoor swimming pool (SP 4) and Standard water (control) have zero toxicity, thus suggesting that that the outdoor pools SP 2, SP 3 and SP 5 were possibly contaminated by chemicals from extraneous sources while contamination of SP 1 was very much negligible, hence the "no observed toxic effect".

Particulate air-borne pollutants in Port Harcourt could contaminate recreational pools; toxicity evaluation and children's health risk assessment.

Air pollution in Port Harcourt metropolis exacerbated by ambient air-borne black soot particles in the past 4 years has become a great concern especially for children who indulge in recreational pools' activities. This study was therefore carried out to evaluate the toxicities of recreational pools in Port Harcourt City and hence perform preliminary health risk assessment. Five recreational pools (4 outdoor and 1 indoor) were used out of the randomly selected 8, from 30 that were identified. Toxicity assessment was carried out using "Ostracods-linked mathematical model" while risk assessment was by analysing protein oxidation and hepatotoxicity in the hepatocytes of exposed rats. Questionnaire-based approach was used to elicit relevant information from children (10-13 years) who consistently engaged in recreational pool activities. The pH and temperature and bacteriological examination of the pools were also carried out. Results show that all the pools were in fairly good sanitary conditions based on the highest mean bacterial counts (2.33±0.57/100 ml), while all were slightly acidic and with normal temperature range. The toxicity indices of outdoor pools (SP 1) and (SP 5) are respectively 20.8 and 49.0 units, while that of outdoor pools (SP 2) and (SP 3) are the same (42.5 units). "No-observed-effect-toxicity" (NOET) was observed for the indoor pool (SP 4). Analysis of the structured questionnaires inferred that none of the children traced has or has had any of the recreational water illnesses. However, results of protein oxidation in rats and hepatotoxicity of rats' hepatocytes suggest that the exposed children may be at oxidative stress-related risks in future especially if the children continue, without adequate precaution, in the use of these pools. It is recommended that further monitoring of these children be continued while measures such as frequent changes of the pool water are ensured.