Occurrence, distribution, and ecological risk assessment of heavy metals in Chao Phraya River, Thailand.

Understanding heavy metals in rivers is crucial, as their presence and distribution impact water quality, ecosystem health, and human well-being. This study examined the presence and levels of nine heavy metals (Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) in 16 surface water samples along the Chao Phraya River, identifying Fe, Mn, Zn, and Cr as predominant metals. Although average concentrations in both rainy and dry seasons generally adhered to WHO guidelines, Mn exceeded these limits yet remained within Thailand's acceptable standards. Seasonal variations were observed in the Chao Phraya River, and Spearman's correlation coefficient analysis established significant associations between season and concentrations of heavy metals. The water quality index (WQI) demonstrated varied water quality statuses at each sampling point along the Chao Phraya River, indicating poor conditions during the rainy season, further deteriorating to very poor conditions in the dry season. The hazard potential index (HPI) was employed to assess heavy metal contamination, revealing that during the dry season in the estuary area, the HPI value exceeded the critical threshold index, indicating the presence of heavy metal pollution in the water and unsuitable for consumption. Using the species sensitivity distribution model, an ecological risk assessment ranked the heavy metals' HC5 values as Pb > Zn > Cr > Cu > Hg > Cd > Ni, identifying nickel as the most detrimental and lead as the least toxic. Despite Cr and Zn showing a moderate risk, and Cu and Ni posing a high risk to aquatic organisms, the main contributors to ecological risk were identified as Cu, Ni, and Zn, suggesting a significant potential ecological risk in the Chao Phraya River's surface water. The results of this study provide fundamental insights that can direct future actions in preventing and managing heavy metal pollution in the river ecosystem.

The Elemental Characteristics and Human Health Risk of PM2.5 during Haze Episode and Non-Haze Episode in Chiang Rai Province, Thailand.

Fine particle matter (PM2.5) was directly related to seasonal weather, and has become the influencing factor of air quality that is harmful for human health in Chiang Rai province. The aims were determining the elemental composition in PM2.5 and human health risk in haze (March 2021) and non-haze episodes (July-August 2021). Nine elements in PM2.5 were measured by using an Atomic Absorption Spectrophotometer, and an enrichment factor was used to identify the emission source. The results showed that the average concentration of PM2.5 was 63.07 µg/m3 in haze episodes, and 25.00 µg/m3 in a non-haze episode. The maximum concentration was 116.7 µg/m3 in March. The majority of elements originated from anthropogenic sources. In haze episodes, PM2.5 mean concentration was approximately 4.2 times that of the WHO guidelines (15 µg/m3 24 h), and 1.3 times that of the Thai Ambient Air Quality Standard (50 µg/m3). The analysis of backward air mass trajectory showed that transboundary and local sources significantly influenced PM2.5 at the monitoring site in the sampling period. In the health risk assessment, the non-carcinogenic risk of Cd was the highest, with a Hazard Quotient (HQ) of 0.048, and the cancer risk of Cr was classified as the highest cancer risk, with the values of 1.29 × 10-5, higher than the minimum acceptable level.

Quality of sources of drinking water and health among the hill tribe people of northern Thailand.

Poor-quality drinking water can cause numerous health problems, particularly for people who are living with poor economic conditions, have a low educational status and have limited access to safe drinking water, such as the hill tribe people in Thailand. This study aimed to assess the quality of different sources of natural drinking water from the hill tribe villages in northern Thailand. Seventy-two drinking water samples from the hill tribe villages were collected and tested for biological, chemical and physical qualities, which were compared with the standard parameter values for safe drinking water according to the World Health Organization. Total coliform bacteria and fecal coliform bacteria, which represented the biological parameters, were detected in all samples. The physical parameters, which consisted of turbidity (36.1%), iron content (5.5%), color (2.7%) and pH (2.7%), exceeded the standard indications. However, the hazard quotient and hazard index values were less than 1. The hill tribe people are facing the problem of poor-quality drinking water, particularly in terms of biological and physical parameters that exceed the standard values. An effective program for improving access to safe water for the hill tribe people should be developed and implemented immediately.

Particulate matter (PM10) prediction based on multiple linear regression: a case study in Chiang Rai Province, Thailand.

BACKGROUND: The northern regions of Thailand have been facing haze episodes and transboundary air pollution every year in which particulate matter, particularly PM10, accumulates in the air, detrimentally affecting human health. Chiang Rai province is one of the country's most popular tourist destinations as well as an important economic hub. This study aims to develop and compare the best-fitted model for PM10 prediction for different seasons using meteorological factors. METHOD: The air pollution and weather data acquired from the Pollution Control Department (PCD) spanned from the years 2011 until 2018 at two stations on an hourly basis. Four different stepwise Multiple Linear Regression (MLR) models for predicting the PM10 concentration were then developed, namely annual, summer, rainy, and winter seasons. RESULTS: The maximum daily PM10 concentration was observed in the summer season for both stations. The minimum daily concentration was detected in the rainy season. The seasonal variation of PM10 was significantly different for both stations. CO was moderately related to PM10 in the summer season. The PM10 summer model was the best MLR model to predict PM10 during haze episodes. In both stations, it revealed an R2 of 0.73 and 0.61 in stations 65 and 71, respectively. Relative humidity and atmospheric pressure display negative relationships, although temperature is positively correlated with PM10 concentrations in summer and rainy seasons. Whereas pressure plays a positive relationship with PM10 in the winter season. CONCLUSIONS: In conclusion, the MLR models are effective at estimating PM10 concentrations at the local level for each seasonal. The annual MLR model at both stations indicates a good prediction with an R2 of 0.61 and 0.52 for stations 65 and 73, respectively.

Influence of the meteorological conditions and some pollutants on PM10 concentrations in Lamphun, Thailand.

Particulate matter (PM) has been occurring regularly during the dry season in the upper north of Thailand including Lamphun Province that might be influenced by various factors including climatologic and other pollutants. This paper aims to investigate the climatologic and gaseous factors influencing the occurrence of PM10 concentration using Pollution Control Department (PCD) data. The secondary data of 2009 to 2017 obtained from the PCD was used for analysis. We used descriptive statistics, Pearson's correlation coefficient, multiple regression and graphic presentation using R program (R packages of 'open air' and 'ncdf4') and Microsoft Excel Spreadsheet®. In addition, the periodic measurement of PM2.5 and PM10 were investigated to determine the ratio of PM2.5/PM10. The results indicated that haze episodes (daily PM10 concentration always over the PCD standard) normally occur during the dry season from February to April. The maximum concentration was always found in March. The PM10 concentration was negatively associated with relative humidity and temperature while the PM10 concentration showed a strongly positive association with CO and NO2 concentration with correlation values of 0.70 and 0.57, respectively. Furthermore, we found CO and PM10 concentration was associated with ozone concentration. This finding will benefit local communities and the public health sector to provide a warning system for preparation and response plans to react to PM10 episodes in their responsible areas.

Variability of urinary creatinine, specific gravity, and osmolality over the course of pregnancy: Implications in exposure assessment among pregnant women.

Due to dilution status of the urine, chemical concentrations measured in spot urine are frequently adjusted using correction factors, such as creatinine, specific gravity (SG), or osmolarity of the urine. Urinary correction factors, however, can be influenced dramatically by physiological changes such as pregnancy. Details about the variation of urine dilution over the course of pregnancy are not well characterized. In the present study, we investigated the variation of urine correction factors over time among the pregnant women of Korea (n = 69) and Thailand (n = 102). Creatinine, SG, and osmolality were determined in the urine samples obtained in each trimester of the participating women, and were compared by sampling time and by nationality. Implication of the variation in these correction factors was studied using phthalate metabolites measured in the urine samples as model chemicals. Urinary correction factors significantly varied across the trimesters especially in Korean pregnant women: urinary creatinine and osmolality were significantly lower in the third trimester (T3) urine than the first trimester (T1) urine. Urinary creatinine and SG of the T3 urine of Korean pregnant women were also significantly lower than those reported from the non-pregnant women who participated in Korean National Environmental Health Survey (KoNEHS) 2015-2017. Among Thai women, however, these correction factors were rather stable across the pregnancy. Differences in ethnicity, or in behavior such as water consumption amount may partly explain the differences. Temporal changes in these urine correction factors influenced the urinary phthalate metabolite concentrations adjusted for dilution, in both Korean and Thai pregnant women. The present observations show that the variations of urinary correction factors should be considered in exposure assessment of urinary chemicals for pregnant women, in order to circumvent potential bias due to physiological changes occurring during pregnancy, and to reduce errors in exposure classification and association.

Exposure to Heavy Metals in Electronic Waste Recycling in Thailand.

Electronic waste recycling can release heavy metals into the environment and cause adverse health effects. We assessed the association between exposure to heavy metals from electronic waste recycling and the prevalence of asthma in a nested case-control study of 51 subject pairs with and without asthma. House dust, airborne dust, blood, and urine were collected from residents of two neighboring sites in Ubon Ratchathani province, Thailand. Multiple electronic waste-handling activities are conducted in the first site, while the second site is mostly agricultural. Concentrations of chromium, mercury, nickel, and lead in house dust and airborne dust were higher in the electronic waste-handling site (p < 0.05), but levels of exposure were similar in subjects with and without asthma. Although we did not find an association between exposure to these metals and the prevalence of asthma, control measures should be implemented to reduce health risks from long-term exposure to heavy metals.

Drinking Water Investigation of Hill Tribes: A Case Study in Northern Thailand.

Hill tribes are a group of people who live in remote areas in northern Thailand. They typically use untreated water for drinking, that can lead several health problems. The six main hill tribes-Akha, Hmong, Karen, Lahu, Lisu, and Yao-were selected for the study. A validated questionnaire was used for data collection. Water samples were collected from the selected villages and tested for the quality at Mae Fah Luang University, Thailand. Results: the major sources of drinking water were mountain water supplies (74.3%), and commercial bottled water (21.4%). Easy access, sufficiency for the whole year, and food-drug administration sign labeled were the criteria used for selecting sources of drinking water. Colorless and safety were also used as a selection criteria for their drinking water in some tribes. Lisu, Karen, and Hmong treated their drinking water by boiling, while Akha and Lahu stored the water in certain containers to allow particle settling before drinking water without treatment. 42.0% of the water samples had a turbidity values <5 NTU, and total coliform and fecal coliform bacteria were detected in 100.0% of the samples. To prevent water-borne diseases among the hill tribe people, appropriate water treatments such as boiling, filtration, and disinfection are recommended.

Urinary levels of phthalates and DINCH metabolites in Korean and Thai pregnant women across three trimesters.

Phthalates are anti-androgenic chemicals and may cause long-lasting adverse effects on growing fetuses. Understanding their exposure profile during pregnancy, therefore, is of public health importance. Because both behavioral and physiological changes of pregnant women are expected to be substantial, the amount of phthalate exposure is expected to vary significantly over the course of pregnancy. Temporal trend of phthalate exposure during pregnancy, however, is largely unknown, especially in Asian women. The purpose of this study is to investigate the urinary concentrations of metabolites for major phthalates and alternative plasticizers over the course of pregnancy among Korean (n = 81) and Thai women (n = 102). Twenty-four metabolites from 15 plasticizers, such as dimethyl phthalate (DMP), diethyl phthalate (DEP), di-isobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), benzyl butyl phthalate (BBzP), di(2-ethylhexyl) phthalate (DEHP), dioctyl phthalate (DnOP), diisononyl phthalate (DiNP), diisodecyl phthalate (DiDP), di(2-ethylhexyl) terephthalate (DEHTP), and di-(iso-nonyl)-cyclohexane-1,2-dicarboxylate (DINCH), were measured in urine samples collected in each trimester from pregnant women. While the levels of several phthalate metabolites were significantly different by trimester among Korean women, those of Thai women were relatively consistent. Urinary metabolites of DEP and DnOP were higher in Thai pregnant women compared to Korean pregnant women. The detection frequencies of the DINCH metabolite were 67.4% and 44.9% among Korean and Thai pregnant women, respectively. However, the ratio of DINCH to DEHP metabolites was significantly higher in Thai women. According to risk assessment, 11.9% of Korean and 5.3% of Thai women were considered at risk due to phthalate exposure, and DEHP, DnBP and DiBP were identified as major risk drivers. Considering the vulnerability of growing fetuses, further studies are warranted to identify major sources of exposure to these plasticizers during pregnancy.

Hepatic protein Carbonylation profiles induced by lipid accumulation and oxidative stress for investigating cellular response to non-alcoholic fatty liver disease in vitro.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is caused by excessive accumulation of fat within the liver, leading to further severe conditions such as non-alcoholic steatohepatitis (NASH). Progression of healthy liver to steatosis and NASH is not yet fully understood in terms of process and response. Hepatic oxidative stress is believed to be one of the factors driving steatosis to NASH. Oxidative protein modification is the major cause of protein functional impairment in which alteration of key hepatic enzymes is likely to be a crucial factor for NAFLD biology. In the present study, we aimed to discover carbonylated protein profiles involving in NAFLD biology in vitro. METHODS: Hepatocyte cell line was used to induce steatosis with fatty acids (FA) in the presence and absence of menadione (oxidative stress inducer). Two-dimensional gel electrophoresis-based proteomics and dinitrophenyl hydrazine derivatization technique were used to identify carbonylated proteins. Sequentially, in order to view changes in protein carbonylation pathway, enrichment using Funrich algorithm was performed. The selected carbonylated proteins were validated with western blot and carbonylated sites were further identified by high-resolution LC-MS/MS. RESULTS: Proteomic results and pathway analysis revealed that carbonylated proteins are involved in NASH pathogenesis pathways in which most of them play important roles in energy metabolisms. Particularly, carbonylation level of ATP synthase subunit α (ATP5A), a key protein in cellular respiration, was reduced after FA and FA with oxidative stress treatment, whereas its expression was not altered. Carbonylated sites on this protein were identified and it was revealed that these sites are located in nucleotide binding region. Modification of these sites may, therefore, disturb ATP5A activity. As a consequence, the lower carbonylation level on ATP5A after FA treatment solely or with oxidative stress can increase ATP production. CONCLUSIONS: The reduction in carbonylated level of ATP5A might occur to generate more energy in response to pathological conditions, in our case, fat accumulation and oxidative stress in hepatocytes. This would imply the association between protein carbonylation and molecular response to development of steatosis and NASH.

Relationships between Meteorological Parameters and Particulate Matter in Mae Hong Son Province, Thailand.

Meteorological parameters play an important role in determining the prevalence of ambient particulate matter (PM) in the upper north of Thailand. Mae Hong Son is a province located in this region and which borders Myanmar. This study aimed to determine the relationships between meteorological parameters and ambient concentrations of particulate matter less than 10 µm in diameter (PM10) in Mae Hong Son. Parameters were measured at an air quality monitoring station, and consisted of PM10, carbon monoxide (CO), ozone (O3), and meteorological factors, including temperature, rainfall, pressure, wind speed, wind direction, and relative humidity (RH). Nine years (2009⁻2017) of pollution and climate data obtained from the Thai Pollution Control Department (PCD) were used for analysis. The results of this study indicate that PM10 is influenced by meteorological parameters; high concentration occurred during the dry season and northeastern monsoon seasons. Maximum concentrations were always observed in March. The PM10 concentrations were significantly related to CO and O3 concentrations and to RH, giving correlation coefficients of 0.73, 0.39, and -0.37, respectively (p-value < 0.001). Additionally, the hourly PM10 concentration fluctuated within each day. In general, it was found that the reporting of daily concentrations might be best suited to public announcements and presentations. Hourly concentrations are recommended for public declarations that might be useful for warning citizens and organizations about air pollution. Our findings could be used to improve the understanding of PM10 concentration patterns in Mae Hong Son and provide information to better air pollution measures and establish a warning system for the province.

Heavy Metal Contamination Near Industrial Estate Areas in Phra Nakhon Si Ayutthaya Province, Thailand and Human Health Risk Assessment.

Industrial activity is one of the significant sources of environmental contamination with heavy metals, especially in developing countries. Flood can also lead to the distribution of toxic substances into the environment, regarding the Thailand flood in 2011 as some industrial estates are affected, leading to concern about heavy metals from industrial wastewater contamination. We aimed to measure the levels of Cd, Cr, Cu, Ni, Mn, Pb, and Zn in river and stream water, sediment, and fish collected from the area around the industrial estates in Uthai District and Bangpa-in District of Phra Nakhon Si Ayutthaya Province, following the floods of 2011. The results revealed that heavy metal levels in water did not exceed Thailand surface water quality standards, except for Mn levels at one sampling site. Metal levels in sediment and fish samples also did not exceed published standards. The hazard quotient for fish consumption was highest for Ni (0.2178) in Trichopodus trichopterus collected from the area near the industrial estate in Bangpa-in District, while the hazard index from Cd, Cr, and Cu exposure were 0.86966, which was lower than 1, indicating that the health risks for these seven metals were within acceptable ranges.

Trace Elements in Marine Sediment and Organisms in the Gulf of Thailand.

This review summarizes the findings from studies of trace element levels in marine sediment and organisms in the Gulf of Thailand. Spatial and temporal variations in trace element concentrations were observed. Although trace element contamination levels were low, the increased urbanization and agricultural and industrial activities may adversely affect ecosystems and human health. The periodic monitoring of marine environments is recommended in order to minimize human health risks from the consumption of contaminated marine organisms.

Climate variability and dengue hemorrhagic fever in Southeast Sulawesi Province, Indonesia.

To determine the association of climatic factors and dengue hemorrhagic fever and to develop the prediction approach of future dengue transmission. The study used totally monthly dengue hemorrhagic fever cases at Health Office Kendari, Southeast Sulawesi, Indonesia. Monthly meteorological data, consisting of temperature, rainfall, and humidity, was obtained from the Meteorology, Climatology and Geophysics Agency in Kendari district. All data analysis, including Spearman and Poisson distribution, was carried out in R Studio (version 3.3.2) utilizing the R statistical language version 2.15. The highest rate of dengue hemorrhagic fever cases was found in January, February, and March. Temperature averages at lag 2 (p = 0.53, p < 0.0001), lag 3 (p = 0.59, p < 0.0001), and lag 4 (p = 0.41, p < 0.01)) correlated with the incident rate of DHF. The average temperature at lag 2 was found to have a positive impact on the incidence of DHF by Poisson function. This study provides preliminary evidence of the influence of climatic factors on dengue transmission.

Evaluating health risks posed by heavy metals to humans consuming blood cockles (Anadara granosa) from the Upper Gulf of Thailand.

There is global concern about heavy metal contamination in the environment. Adverse health effects can be caused by heavy metals in contaminated food and water. Therefore, environmental monitoring studies and risk assessments should be conducted periodically. In this study, we measured levels of Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn in blood cockles (Anadara granosa) collected from three locations in the Upper Gulf of Thailand. Hazard quotients and hazard indices were calculated to evaluate the health risks posed by heavy metals in consumed blood cockles. Heavy metal concentrations in all of the blood cockle samples were lower than the relevant food standards. The hazard quotients and hazard indices were <1 in all three sampling areas, indicating that adverse health effects were not likely to be caused by exposure to heavy metals in blood cockles over a human lifetime.

Effect of Temperature on Fimbrial Gene Expression and Adherence of Enteroaggregative Escherichia coli.

The influence of temperature on bacterial virulence has been studied worldwide from the viewpoint of climate change and global warming. The bacterium enteroaggregative Escherichia coli (EAEC) is the causative agent of watery diarrhea and shows an increasing incidence worldwide. Its pathogenicity is associated with the virulence factors aggregative adherence fimbria type I and II (AAFI and AAFII), encoded by aggA and aafA in EAEC strains 17-2 and 042, respectively. This study focused on the effect of temperature increases from 29 °C to 40 °C on fimbrial gene expression using real-time PCR, and on its virulence using an aggregative adherence assay and biofilm formation assay. Incubation at 32 °C caused an up-regulation in both EAEC strains 17-2 and strain 042 virulence gene expression. EAEC strain 042 cultured at temperature above 32 °C showed down-regulation of aafA expression except at 38 °C. Interestingly, EAEC cultured at a high temperature showed a reduced adherence to cells and an uneven biofilm formation. These results provide evidence that increases in temperature potentially affect the virulence of pathogenic EAEC, although the response varies in each strain.

Contamination of nitrate in groundwater and its potential human health: a case study of lower Mae Klong river basin, Thailand.

Nitrate contamination in groundwater is a worldwide problem especially in agricultural countries. Environmental factors, such as land-use pattern, type of aquifer, and soil-drainage capacity, affect the level of contamination. Exposure to high levels of nitrate in groundwater may contribute to adverse health effects among residents who use groundwater for consumption. This study aimed to determine the relationship between nitrate levels in groundwater with land-use pattern, type of aquifer, and soil-drainage capacity, in Photharam District, Ratchaburi Province, lower Mae Klong basin, Thailand. Health risk maps were created based on hazard quotient to quantify the potential health risk of the residents using US Environmental Protection Agency (U.S. EPA) health risk assessment model. The results showed the influence of land-use patterns, type of aquifer, and soil-drainage capacity on nitrate contamination. It was found that most of the residents in the studied area were not at risk; however, a groundwater nitrate monitoring system should be implemented.

Biomonitoring of heavy metals among nielloware workers in Nakhon Sri Thammarat Province.

OBJECTIVE: To determine lead and mercury concentrations in biological samples from nielloware workers, to describe the association between occupational lifestyle, workposition, work environment, behavioral factors, acute and chronic neurological symptoms, and levels of metals in biological samples. MATERIAL AND METHOD: A cross-sectional study was conducted by interviewing 45 nielloware workers and 45 matched nonexposed persons living in the municipality of Nakhon Si Thammarat Province, Thailand. Blood and urine samples were collected to determine lead and mercury concentrations by atomic absorption spectrophotometer. RESULTS: The blood lead levels (7.30 microg/dl) and urinary mercury levels (3.30 microg/g creatinine) of the nielloware workers were significantly higher than the control group (p < 0.001). Income, working environmental conditions, workposition, duration of work, personal protective equipment (PPE) and personal hygiene, had significant associations with blood lead and urinary mercury levels (p < 0.05). A significant positive correlation was found between income and blood-lead level (r = 0.968, p < 0.001) and urinary-mercury level (r = 0.661, p = 0.004). The nielloware workers developed acute and chronic symptoms, such as headaches, rash, fatigue, tightness in the chest, loss of consciousness, abnormal tiredness and headache at least once a week and those who developed symptoms had significantly higher heavy metal levels than those who did not at p < 0.05. CONCLUSION: The blood lead and urinary mercury levels in nielloware workers were significantly higher than those in the control subjects. The significant associations were found between income, work position, PPE and personal hygiene and blood lead and urinary mercury levels.

gyrA and gyrB mutations in ofloxacin-resistant Mycobacterium tuberculosis clinical isolates in Thailand.

In order to identify mutations in gyrA and gyrB genes in 92 ofloxacin-resistant Mycobacterium tuberculosis (OFXr-MTB) clinical isolates collected from Siriraj Hospital, Mahidol University and Chest Disease Institute, Thailand. The quinolone resistance-determining regions (QRDR) of gyrA and gyrB in all 92 OFXr-MTB isolates were amplified using polymerase chain reaction and sequenced. There were 70 isolates with point mutations associated with ofloxacin resistance. In gyrA QRDR, 69 isolates had mutations in gyrA Gly88 (Ala/(75), Ala90 (Val), Ser91 (Pro) and Asp94 (Gly/Ala/His/Asn), the latter being the most common (42%). Only one isolate was found with mutation at position Asp495 (Asn). The other 22 isolates had no mutations in both gyrA and gyrB QRDR. Thus, point mutations in gyrA and gyrB QRDR were responsible for OFXr-MTB clinical isolates in Thailand.

Evaluation of an electronic air filter for filtrating bacteria and viruses from indoor air.

This study compared the filtrating efficiency (FE) of a commercial electronic air filter for filtering bacteria and viruses from contaminated air with a high efficiency particulate air (HEPA) filter. An enclosed chamber was constructed, in the middle of which an air filter was placed for testing. MTB H37Ra and T7 virus at concentrations of 5x10(8) each were sprayed into one side of the chamber using a nebulizer and the sprayed samples were collected by an impinger air-sampler on the other side. MTB and T7 viruses were detected by PCR and culture. The PCR could detect samples down to 10 fg for MTB H37Ra and 1 pg for T7 virus. Most MTB H37Ra sprayed failed to culture. S. aureus at a concentration of 10(5) cfu and E. coli at a concentration of 10(4) cfu along with T7 virus were filtered out with a FE of more than 99%. T7 virus has a particle size of 0.04 microm, S. aureus has a particle size of 1 microm and E. coli has a particle size of 2 microm.