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  1. Muzaini K, Yasin SM, Ismail Z, Ishak AR
    Front Public Health, 2021;9:646790.
    PMID: 33763402 DOI: 10.3389/fpubh.2021.646790
    Background: Sewage workers have a higher risk of exposure to various potential occupational respiratory hazards found in sewage plants. Although previous studies discuss occupational respiratory hazard concentration impacting sewage workers' respiratory health, the results are scarce and mixed. Hence, there is a need to identify the potential respiratory hazards in sewage plants so as to clarify the short- and long-term respiratory health effects. Therefore, this systematic review (SR) aims to critically review previous studies investigating potential respiratory hazards found at sewage plants and their effects on sewage workers' respiratory health. Methods: An SR was conducted using PubMed, EBSCO Medline, Web of Science, Scopus, and Google Scholar on peer-reviewed studies published between January 1994 and October 2020 evaluating the impact of potential exposure to respiratory hazards and its effects on respiratory health among sewage workers. "Sewage treatment plant," "respiratory hazards," and "respiratory health effects" were the three main search terms chosen in this SR. The inclusion criteria were (1) studies on potential occupational respiratory hazard exposure among sewage workers, (2) manuscripts written in English, and (3) studies published in the peer-reviewed literature. The human observational studies' quality was assessed using the Effective Public Health Practice Project Quality Assessment Tool. Results: We identified 5,660 articles through an initial database search. Only 26 items met the inclusion criteria and were included in this review; 15 human observational studies and 11 environmental assessment studies were conducted in the sewage industries. Most of the human observational studies were rated as moderate quality, two studies were rated as weak quality, and one study with strong quality was identified. Hydrogen sulfide, bioaerosols, particulate matter 2.5 (PM 2.5), and volatile organic compounds (VOC) were found to be potential respiratory hazards. Most of the risks contributed to adverse outcomes on the sewage workers' respiratory health with some inconsistent findings on the relationship between respiratory hazard exposure and respiratory health effects. Conclusion: Our review finds that, although this area is of great importance, quality studies are still lacking. There is a need for additional studies to clarify the effects of respiratory hazard exposure on sewage workers and respiratory health, especially PM 2.5 and VOC.
  2. Ishak AR, Hamid FS, Mohamad S, Tay KS
    Waste Manag, 2018 Jun;76:575-581.
    PMID: 29503052 DOI: 10.1016/j.wasman.2018.02.047
    In this work, the feasibility of coagulation-flocculation coupled with UV-based sulfate radical oxidation process (UV/SRAOP) in the removal of chemical oxygen demand (COD) of stabilized landfill leachate (SLL) was evaluated. For coagulation-flocculation, ferric chloride (FeCl3) was used as the coagulant. The effect of initial pH of SLL and COD:FeCl3 ratio on the COD removal was evaluated. The result revealed that COD:FeCl3 ratio of 1:1.3 effectively removed 76.9% of COD at pH 6. The pre-treated SLL was then subjected to UV/SRAOP treatment. For UV/SRAOP, the sulfate radical (SR) was generated using UV-activated persulfate (UV/PS) and peroxymonosulfate (UV/PMS). The dosage of oxidant and reaction time were found to be the main parameters that influence the efficiency of COD removal. On the other hand, the effect of initial pH (3-7) and the type of oxidant (PS and PMS) was found to have no significant influence on COD removal efficiency. At optimum conditions, approximately 90.9 and 91.5% of COD was successfully removed by coagulation-flocculation coupled with UV/PS and UV/PMS system, respectively. Ecotoxicity study using zebrafish showed a reduction in toxicity of SLL from 10.1 to 1.74 toxicity unit (TU) after coagulation-flocculation. The TU remained unchanged after UV/PS treatment but slightly increased to 1.80 after UV/PMS treatment due to the presence of residual sulfate ion in the treated effluent. In general, it can be concluded that coagulation-flocculation coupled with UV/SRAOP could be a potential water treatment method for SLL treatment.
  3. Ishak AR, Hamid FS, Mohamad S, Tay KS
    Waste Manag Res, 2017 Jul;35(7):739-746.
    PMID: 28539097 DOI: 10.1177/0734242X17707572
    The treatment of stabilized landfill leachate (SLL) by conventional biological treatment is often inefficient due to the presence of bio-recalcitrant substances. In this study, the feasibility of coagulation-flocculation coupled with the Fenton reaction in the treatment of SLL was evaluated. The efficiency of the selected treatment methods was evaluated through total organic carbon (TOC) removal from SLL. With ferric chloride as the coagulant, coagulation-flocculation was found to achieve the highest TOC removal of 71% at pH 6. Then, the pretreated SLL was subjected to the Fenton reaction. Nearly 50% of TOC removal was achieved when the reaction was carried out at pH 3, H2O2:Fe2+ ratio of 20:1, H2O2 dosage of 240 mM and 1 h of reaction time. By coupling the coagulation-flocculation with the Fenton reaction, the removal of TOC, COD (chemical oxygen demand) and turbidity of SLL were 85%, 84% and 100%, respectively. The ecotoxicity study performed using zebrafish revealed that 96 h LC50 for raw SLL was 1.40% (v/v). After coagulation-flocculation, the LC50 of the pretreated SLL was increased to 25.44%. However, after the Fenton reaction, the LC50 of the treated SLL was found to decrease to 10.96% due to the presence of H2O2 residue. In this study, H2O2 residue was removed using powdered activated charcoal. This method increased the LC50 of treated effluent to 34.48% and the removal of TOC and COD was further increased to 90%. This finding demonstrated that the combination of the selected treatment methods can be an efficient treatment method for SLL.
  4. Ibrahim F, Samsudin EZ, Ishak AR, Sathasivam J
    Front Public Health, 2022;10:1067764.
    PMID: 36424957 DOI: 10.3389/fpubh.2022.1067764
    Indoor air quality (IAQ) has recently gained substantial traction as the airborne transmission of infectious respiratory disease becomes an increasing public health concern. Hospital indoor environments are complex ecosystems and strategies to improve hospital IAQ require greater appreciation of its potentially modifiable determinants, evidence of which are currently limited. This mini-review updates and integrates findings of previous literature to outline the current scientific evidence on the relationship between hospital IAQ and building design, building operation, and occupant-related factors. Emerging evidence has linked aspects of building design (dimensional, ventilation, and building envelope designs, construction and finishing materials, furnishing), building operation (ventilation operation and maintenance, hygiene maintenance, access control for hospital users), and occupants' characteristics (occupant activities, medical activities, adaptive behavior) to hospital IAQ. Despite the growing pool of IAQ literature, some important areas within hospitals (outpatient departments) and several key IAQ elements (dimensional aspects, room configurations, building materials, ventilation practices, adaptive behavior) remain understudied. Ventilation for hospitals continues to be challenging, as elevated levels of carbon monoxide, bioaerosols, and chemical compounds persist in indoor air despite having mechanical ventilation systems in place. To curb this public health issue, policy makers should champion implementing hospital IAQ surveillance system for all areas of the hospital building, applying interdisciplinary knowledge during the hospital design, construction and operation phase, and training of hospital staff with regards to operation, maintenance, and building control manipulation. Multipronged strategies targeting these important determinants are believed to be a viable strategy for the future control and improvement of hospital IAQ.
  5. Ibrahim F, Samsudin EZ, Ishak AR, Sathasivam J
    Heliyon, 2024 Jul 30;10(14):e34454.
    PMID: 39082032 DOI: 10.1016/j.heliyon.2024.e34454
    INTRODUCTION: Poor indoor air quality (IAQ) in healthcare settings may adversely impact occupants' well-being and promote transmission of infectious respiratory disease. However, evidence on its potentially modifiable determinants, including occupant behaviour, remains scarce. This study aims to determine the relationship between occupant behaviour and IAQ in Malaysian hospital outpatient departments (OPDs).

    METHODS: A multistage cross-sectional study of six randomly selected Malaysian public hospital OPDs was conducted. In stage one, IAQ parameters, including temperature, relative humidity (RH), air velocity (AV), carbon dioxide (CO2), total bacterial count (TBC), and total fungal count (TFC) were measured. In stage two, an observation form based on the Korsavi and Montazami tool for measuring adaptive behaviour was used to examine occupant density, activities, and operation of building envelopes and appliances. Simple correlation, partial correlation, and linear regression analyses were performed to examine the relationship between occupant behaviour and IAQ parameters.

    RESULTS: The IAQ of selected hospital OPDs complied with established standards, except for temperature and AV. Occupant density was positively correlated with temperature and CO2. Meanwhile, occupants' activities including slow walking and brisk walking were positively correlated with temperature, AV, CO2, TBC and TFC. Conversely, occupants' opening of windows and doors were positively correlated with temperature and AV but negatively correlated with CO2, TBC and TFC. Finally, turning on fans was positively correlated with AV but negatively correlated with TBC, whereas turning on air conditioner was positively correlated with CO2. Among occupants' behaviour, opening of windows and doors contributed the most to variation in IAQ parameters.

    CONCLUSIONS: The study findings suggest that IAQ in hospital OPDs are influenced by occupant density, activities, and operation of doors, windows, and appliances. Prospective hospital IAQ guidelines should incorporate policies and measures targeting these factors to ensure occupants' best practices in maintaining healthy hospital indoor air environments.

  6. Mohd Hussain RH, Ishak AR, Abdul Ghani MK, Ahmed Khan N, Siddiqui R, Shahrul Anuar T
    J Water Health, 2019 Oct;17(5):813-825.
    PMID: 31638031 DOI: 10.2166/wh.2019.214
    This study aimed to identify the Acanthamoeba genotypes and their pathogenic potential in five recreational hot springs in Peninsular Malaysia. Fifty water samples were collected between April and September 2018. Physical parameters of water quality were measured in situ while chemical and microbiological analyses were performed in the laboratory. All samples were filtered through the nitrocellulose membrane and tested for Acanthamoeba using both cultivation and polymerase chain reaction (PCR) by targeting the 18S ribosomal RNA gene. The pathogenic potential of all positive isolates was identified using thermo- and osmotolerance tests. Thirty-eight (76.0%) samples were positive for Acanthamoeba. Water temperature (P = 0.035), chemical oxygen demand (P = 0.026), sulphate (P = 0.002) and Escherichia coli (P < 0.001) were found to be significantly correlated with the presence of Acanthamoeba. Phylogenetic analysis revealed that 24 samples belonged to genotype T4, nine (T15), two (T3) and one from each genotype T5, T11 and T17. Thermo- and osmotolerance tests showed that 6 (15.79%) of the Acanthamoeba strains were highly pathogenic. The existence of Acanthamoeba in recreational hot springs should be considered as a health threat among the public especially for high-risk people. Periodic surveillance of hot spring waters and posting warning signs by health authorities is recommended to prevent disease related to pathogenic Acanthamoeba.
  7. Brohan MA, Dom NC, Ishak AR, Abdullah S, Salim H, Ismail SNS, et al.
    Environ Sci Pollut Res Int, 2021 Dec;28(46):66501-66509.
    PMID: 34665420 DOI: 10.1007/s11356-021-17049-6
    This study intends to deal with the environmental consequences of the COVID-19 pandemic in Malaysia, by providing a summary of the effects of COVID-19 on municipal solid waste (MSW). In this analysis, the data on domestic waste collection were collected from the Solid Waste Management and Public Cleaning Corporation (SWCorp) from 1 January 2020 to 31 December 2020 to evaluate the relative changes in MSW percentage via a waste weighing method. The data consisted of the cumulative tonnage of MSW for every local authority in Peninsular Malaysia and was classified according to MCO phases; before the MCO, during the MCO, during the conditional MCO (CMCO) and during the recovery MCO (RMCO) phases. The results indicated that the enforcement of the early MCO showed a positive effect by decreasing the volume of MSW. This decrease was noted across 41 local authorities, which accounts for 87.23% of Peninsular Malaysia. However, the amount of MSW began to increase again when the MCO reached the conditional and recovery stages. From this, it can be concluded that the implementation of the MCO, in its various incarnations, has shown us that our lifestyles can have a harmful impact on our environment. While the pandemic was still spreading and limitations were still in place in Malaysia, local governments and waste management companies had to quickly alter their waste management systems and procedures. The current circumstance allows us to rethink our social and economic structures while improving environmental and social inclusion.
  8. Sidek SS, Yatim SRM, Abdullah S, Shafie FA, Ishak AR, Dom NC, et al.
    Med J Malaysia, 2024 Mar;79(Suppl 1):104-109.
    PMID: 38555893
    BACKGROUND: Indoor air quality is an important concern for kindergartener because young children are more vulnerable to the effects of poor air quality. Poor indoor air quality can cause respiratory problems and other health issues, which can negatively affect a child's ability to learn and grow. Aim of this study is to determine the trend and status of indoor air pollutants in study areas by using descriptive statistics and cluster analysis.

    MATERIALS AND METHODS: Air temperature (T), relative humidity (RH), air movement (AM), carbon dioxide (CO2), formaldehyde (HCHO), and particulate matter (PM) are the monitored parameters. Monitoring was carried out in the kindergarten for three consecutive days starting from 8.00am to 12.00pm.

    RESULTS: Indoor carbon dioxide readings were higher at 0800 when parents drove to kindergarten to drop off their children without turning off the engine. In addition to this, the PM10 reading at 1000 was high but still within the standard range according to ICOP-IAQ 2010.

    CONCLUSION: The findings highlight the importance of indoor air quality improvement measures for kindergarten buildings which can be used to improve indoor air quality in kindergarten environments.

  9. Aziz MY, Hussain SH, Ishak AR, Abdullah MA, Mohamed R, Ruzi II, et al.
    Biol Trace Elem Res, 2021 Sep 30.
    PMID: 34591221 DOI: 10.1007/s12011-021-02942-5
    The presence of heavy metals in human hair is being tracked to predict health risk, forensics, and environmental monitoring. Heavy metals are typically non-biodegradable and have a lengthy half-life, allowing them to linger in humans and the environment for many years. Heavy metal exposure in hair has been attributed to multiple sources from the environment and food intake. In this study, copper (Cu), nickel (Ni), zinc (Zn), chromium (Cr), manganese (Mn), lead (Pb), and cadmium (Cd) levels were measured in the scalp hair of 50 individuals in Bukit Mertajam, Penang, Malaysia. In conjunction with sampling, subjects' age, gender, lifestyle, diet, and working environment were also obtained through the questionnaire. The Atomic Absorption Spectrometry (AAS) method was used to extract all the metals in the hair samples. The mean concentrations of heavy metals were found to be in the following order (unit of mg/kg): Cr > Zn > Pb > Ni > Cd > Cu. Manganese was detected below the limit of quantitation among the elements (
  10. Cheong NDH, Mohamed E, Haron N, Camalxaman SN, Abdullah A, Mohamad Yusof MI, et al.
    Med J Malaysia, 2024 Mar;79(Suppl 1):34-39.
    PMID: 38555883
    INTRODUCTION: Parkia speciosa Hassk., commonly known as bitter bean or twisted cluster bean, is a tropical leguminous plant species native to Southeast Asia. The plant's edible pods have been traditionally used in various cuisines, particularly in Malaysian, Thai, and Indonesian cooking. Apart from being used as a food ingredient, the pods of P. speciosa also have a range of potential applications in other fields, including medicine, agriculture, and industry. The pods are said to have several phytochemicals that hold great therapeutic values such as reducing inflammation, improving digestion, and lowering blood sugar levels. However, there is limited information on the specific phytochemical contents of the pods in the literature. Thus, the aim of this study is to quantify the total phenolic and flavonoid compounds and to determine the concentrations of four selected phytochemical compounds in the P. speciosa pod extract (PSPE).

    MATERIALS AND METHODS: Quantification of the total phenolic (TPC) and flavonoid contents (TFC) in PSPE were done via colourimetric methods; and the determination of the concentrations of four specific phytochemicals (gallic acid, caffeic acid, rutin, and quercetin) were done via High- Performance Liquid Chromatography (HPLC).

    RESULTS: Colourimetric determination of PSPE showed TPC and TFC values of 84.53±9.40 mg GAE/g and 11.96±4.51 mg QE/g, respectively. Additional analysis of the phytochemicals using HPLC revealed that there were 6.45±3.36 g/kg, 5.91±1.07 g/kg, 0.39±0.84 g/kg, and 0.19±0.47 g/kg of caffeic acid, gallic acid, rutin, and quercetin, respectively.

    CONCLUSION: The findings show that PSPE contains substantial amounts of caffeic acid, gallic acid, rutin, and quercetin, which may indicate its potential as antibacterial, anti-inflammatory, anti-lipid, and antiviral medicines.

  11. Kari ZA, Téllez-Isaías G, Hamid NKA, Rusli ND, Mat K, Sukri SAM, et al.
    Aquac Nutr, 2023;2023:6676953.
    PMID: 39553242 DOI: 10.1155/2023/6676953
    Insects such as black soldier fly larvae (BSFL) are gaining interest among researchers and the aquafeed industry due to the fluctuating price and supply of fish meal (FM). This study evaluated the growth performance, feed stability, blood biochemistry, and liver and gut morphology of Betta splendens using BSFL as an alternative to FM. Five formulated diets were prepared: 0% BSFL, 6.5% BSFL, 13% BSFL, 19.5% BSFL, and 24.5% BSFL. The expansion rate, pellet durability index, floatability, bulk density, and water stability of the prepared feed have been assessed. Except for the diameter of the feed, all the parameters studied differed significantly (p < 0.05) across the experimental diets. After 60 days, the fish fed with 13% BSFL had the highest final length, final weight, net weight gain, specific growth rate, weight gain, and gastrointestinal weight, with mean and standard deviation values of 3.97 ± 0.43 cm, 3.95 ± 0.1 g, 2.78 ± 0.1 g, 4.63 ± 0.17, 4.65 ± 0.13, 237.26 ± 7.9%, and 0.04 ± 0.01 mg, respectively. Similar blood haematology and biochemical properties, including corpuscular volume, lymphocytes, white blood cells, red blood cells, haematocrit, albumin, and alkaline phosphatase, were the highest (p < 0.05) in the 13% BSFL diet group compared to the other treatment groups. In addition, BSFL had a significant impact (p < 0.05) on villus length, width, and crypt depth for the anterior and posterior guts of B. splendens. The 13% BSFL diet group had an intact epithelial barrier in the goblet cell arrangement and a well-organized villus structure and tunica muscularis, compared to the other treatment groups. Furthermore, the liver cell was altered with different BSFL inclusions; the 13% FM group demonstrated better nuclei and cytoplasm structure than the other treatment groups. In conclusion, replacing 13% FM with BSFL could improve the growth performance, blood parameters, and liver and intestine morphology of B. splendens, thus providing a promising alternative diet for ornamental freshwater fish.
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