Objectives: This dissertation studied the time trends and distribution of fatal and non-fatal childhood drowning in Malaysia by demographic and spatial factors between 2000 and 2022. The difference in annual incidence between 2000-2011 and 2012-2022 was also identified. Methods: The drowning data reported to the national Health Informatics Centre (HIC) for 18 years old and below, from hospitalised cases of child drowning incidents and drowning deaths, were analysed. Data from the Department of Statistics Malaysia (DOSM) were also retrieved. These data were then used to calculate annual incidence, annual rates of change in drowning, and case fatality rates. Also, binary logistic regression analyses identified the socio-demographic and spatial factors associated with drowning. The outcome or the dependent variables were fatal and non-fatal, while age, year, sex, race, and region acted as independent variables. Results: A total of 4,191 reports of childhood drowning incidents and 155 drowning fatalities were reported to HIC. Drowning incidence rate was higher in 2000-2011 (IR 21.83) than in 2012-2022 (IR 17.65). Drowning incidence were significantly higher among the aged 0-4 years, boys, Bumiputera, and children living in urban areas (p<0.001). In contrast, the case fatality rate was higher in 2012-2022 (CFR 4.88) than in 2000-2011 (CFR 2.75). Children aged 0-9 years (p<0.001), children living in the Klang Valley region (p=0.049), and urban areas (p=0.034) were significant in fatal drowning. The time trends analysis for annual rates of change increased by 0.0001 for drowning incidents and 0.0003 for drowning fatalities. The east coast region significantly demonstrates 2.19 times (95% CI 1.03-4.65) higher than other regions (p=0.0041). Conclusions: This study provided more detail analyses of available childhood drowning data. The null hypothesis was rejected as there was a difference of drowning incidents in 2000-2011 and 2012-2022. The findings also suggested that preventive measures should be targeted towards children aged 0-9 years, boys, and children living in urban areas.

Airborne algae and cyanobacteria (AAC) have received much attention as their occurrence have been documented in several studies, including indoor environment. There has been concern whether AAC can trigger allergic response and thus, they may have ill health effects, especially in relation to sick building syndrome (SBS). There have been very few studies reported on the allergenicity of AAC. The main objective of this study was to assess the allergenic potential of three AAC, namely Scenedesmus sp., Cylindrospermum sp. and Hapalosiphon sp.1, which were isolated from an office building in Kuala Lumpur. The study was based on a mouse model, with the suspension of AAC powder in phosphate buffered saline (PBS) administered via nasal route. Naïve mice were sensitised to 1 mg/mL of AAC for 10 consecutive days during Phase I immunisation. In Phase II immunisation which was given after five resting weeks, the mice were re-challenged with 20 μL of AAC at two concentrations (0.01 and 1 mg/mL) for three consecutive days before they were sacrificed. The immune response was assessed based on white blood cell profiles, quantification of humoural and intracellular expression of IgE, TH2 predominant and inflammatory cytokines and histopathological examination. In general, the three AAC elicited greater immune response in mice challenged with high (1 mg/mL) concentration of AAC than with low (0.01 mg/mL) concentration. In mice challenged with Scenedesmus sp. at both low and high concentrations, there were elevated peripheral eosinophil and monocyte counts. Significantly higher levels of serum IgE (P<0.05) and IFN-γ (P<0.05) compared to negative control were also observed. The data collected 48 h after the last dose of immunisation also indicated possible cause of allergic airway inflammation, a chronic manifestation of respiratory allergy upon nasal exposure to the algal particles. On the other hand, Cylindrospermum sp. and Hapalosiphon sp.1 did not elicit type-1 hypersensitivity as both eosinophil counts and serum IgE levels were not elevated in the sensitised mice. The results suggest that the two airborne cyanobacteria provoked immune response differently. In mice challenged with Cylindrospermum sp. (1 mg/mL), there were elevated serum IL-4 (22.1 pg/mL, P<0.05). However, the increase in peripheral neutrophil counts (9.2%) against Cylindrospermum sp. (1 mg/mL) was not significant when negative control was compared. In comparison, in mice challenged with Hapalosiphon sp.1, there were elevations of serum IL-6 (4.8 pg/mL, P<0.05) yet the observed increase of peripheral lymphocyte counts (9.2%) was not statistically significant. In addition, the elevations in serum IFN-γ levels were highest in mice nasal challenged with Cylindrospermum sp. (71.9 pg/mL, P<0.05), followed by Hapalosiphon sp.1 (50.6 pg/mL, P<0.05). Taken together, the results suggest that nasal exposure to Cylindrospermum sp. and Hapalosiphon sp.1 may provoke inflammatory immune responses in the airway. Further studies are warranted to assess the potential health impact due to the allergenic potential of the AAC, especially with regards to the effect of continual exposure to low concentration of the algal particles over extended period of time.