Health implication among occupational exposed workers in a chromium alloy factory, Thailand.

This study was conducted to assess the occupational exposure and its health impact on the chromium alloy workers. Environmental and biological monitoring, noise and audiometry measurements were done to evaluate the exposure levels in the factory. A total of 112 non-smoking workers were monitored from July 2001 to August 2002. The results showed that most of the chromium and lead exposures in the factory were below the ACGIH-TWA of 50 microg/m3 for chromium(VI) and OSHA-PEL of 50 microg/m3 for lead. The highest chromium (7.25 +/- 0.16 microg/m3) and lead (14.50 +/- 0.29 microg/m3) concentrations were measured in the vibro room. The results indicated that elevated concentrations of chromium and lead were found in both blood and urine samples especially in those areas which were characterized by poor ventilation. The metal contents in blood and urine samples were significantly correlated with airborne metal concentrations in the factory. The result demonstrated that blood and urinary levels among workers were associated with increasing age and duration of exposure. The background noise level of the factory ranged from 67.6 to 89.2 dBA and was frequently higher than the threshold limit value for noise (90 dBA). According to the audiometric test, the exposed workers showed signs of noise-induced hearing loss. Noise at work continued to be an important factor to hearing loss among exposed workers. In our statistical analysis, a significant hearing loss was established on age effect and year of exposure among the workforce.

Benzene and lead exposure assessment among occupational bus drivers in Bangkok traffic.

Four environmental and biological monitoring sites were strategically established to evaluate benzene and lead exposure assessment at various traffic zones of Bangkok Metropolitan Region(BMR). Biological measurement of 48 non air-conditioned, male bus drivers was carried to study the relationship between individual exposure levels and exposure biomarkers. The study group was further subdivided into four age groups(16-25, 26-35, 36-45 and 46-55 years old) to monitor the age-related exposure effects. A total of 12 unexposed persons were deliberately chosen as the control group. Measurement of unmetobolized benzene in blood and analysis of urinary tt-Muconic acid urine and urinary creatinine are recommended as biomarkers of benzene exposure. Measurement of lead in blood and urine is also recommended for the biological monitoring of lead exposure. During the monitoring period, benzene and lead levels at Yaowarat Road was C6H6: 42.46 +/- 3.88 microg/m3 , Pb: 0.29 +/- 0.03 microg/m3 and decreased to C6H6: 33.5 +/- 1.35 microg/m3, Pb: 0.13 +/- 0.01 microg/m3 at Phahonyothin Road. Significant difference was established between the nonsmoking exposed group and nonsmoking control group for blood benzene concentrations (P < 0.001, two-tailed, Mann-Whiteney U test). Strong correlations were also found between trans-trans-Muconic acid concentrations in post shift samples and atmospheric benzene concentrations. Similarly, good correlation between all of biomarkers and lead level in air is established from automobile emissions. The analysis revealed that among the occupational population in the urban sites, the driver groups were found to have the highest risk of benzene and lead exposures derived from automobile emission.

Regional monitoring of lead and cadmium contamination in a tropical grazing land site, Thailand.

An investigation was carried out to monitor Pb and Cd contamination in grazing land located near a highway. Environmental media at different distances from highway (soil, grass, water, cow's forage, fertilizer, manure and milk samples) were collected from three sampling locations. Soil and grass were characterized by high metal mobility (soil with Pb: 5.25 +/- 0.71-14.59 +/- 1.17 mg kg(-1), dry mass and Cd: 0.038-0.33 +/- 0.04 mg kg(-1), dry mass and grass with Pb: 0.76 +/- 0.05-6.62 +/- 0.18 mg kg(-1), dry mass and Cd: 0.17+/- 0.01-0.73 +/- 0.09 mg kg(-1), dry mass). One-way analysis of variane (ANOVA) was applied to find out the correlation between metal (total and bioavailable) concentrations in the soil and the distance from roadside. In most cases, the finding showed that plants growing nearer to the highway are usually exposed to more heavy metal accumulations than those away from the highway. In addition, a correlation was established between plant available metal concentrations and plant metal uptake concentrations. Analysis of fertilizer and manure showed considerable amount of metals (fertilizer with Pb: 1.53 +/- 0.06 mg kg(-1) and Cd: 0.038 mg kg(-1) and manure with Pb: 2.55-3.34 mg kg(-1) and Cd: 0.14-0.31 mg kg(-1)). Long-.term simultaneous application of fertilizer and manure on the commercial farm showed higher metal accumulation in the soil and plants than those of co-operative farm. Considerable concentrations of metals (Pb: 1.60-2.94 mg kg(-1) and Cd: 0.025-0.19 mg kg(-1)) were observed in fodder. The finding clearly demonstrated that there are seasonal variation in total daily metal intake by individual cow (Pb: 109.37 mg day(-1) (dry), 273.47 mg day(-1) (rainy) and Cd: 2.02 mg day(-1) (dry), 19.62 mg day(-1) (rainy)). The provisional tolerable weekly intake of heavy metals in cows is 390 microg Pb and 28 microg Cd per kg body weight in the rainy season and 156 microg Pb and 2 microg Cd per kg body weight in the dry season. The levels of metals (Pb: 0.014 mg L(-1) and Cd: not detectable) and bio-transfer factor (10(-5)-10(-4)) in raw milk were found to be well below the Codex Alimentarius Commissions Draft (1997). Our analysis revealed that improvements on farm management give significant reduction in elevated levels of Pb and Cd in soil and plants, and however leads to minimize the amount of Pb and Cd in consumed milk.

Monitoring and assessment of daily exposure of roadside workers to traffic noise levels in an Asian city: a case study of Bangkok streets.

Four noise monitoring sites were strategically established to evaluate average noise level and audiometric assessment at various traffic zones of Bangkok Metropolitan Region (BMR). During the monitoring period, noise levels were found to be 72.8-83.0 dBA during day time and 59.5-74.5 dBA during night time. The finding also indicated that traffic noise levels depend on distance from roadside, diurnal variation and character of the traffic and street configuration. Audiometric measurement of 4000 persons was carried by four major hospitals in Bangkok to study the relationship between traffic noise exposure of groups of people working in the streets and hearing loss. Four different categories of occupational people, i.e., drivers, street vendors, traffic officers and dwellers were selected and were further classified into age groups (16-25, 26-35, 36-45 and 46-55 years old) to monitor the traffic noise induced hearing loss throughout their everyday lives. The control group was deliberately chosen to screen out the effects of traffic noise. According to the audiometric investigation, it was revealed that hearing capacity of the daily noise exposure groups living in the three urban sites (Yaowarat Road, Din Daeng Road and Ratchaprarop Road) were noticeably poorer than those who were living in suburban site (Phahonyothin Road). It was noted that the mean hearing threshold level (HTL) of the 16-25 years old groups were found to have better hearing capacity than those older adults of 46-55 years old. In particular the mean HTL dropped at the frequency of 4000 Hz. Among the occupational population who were living in the urban monitoring sites, the driver groups were found to have the highest risk of traffic noise induced hearing loss.

Indicators of benzene emissions and exposure in Bangkok street.

Ambient benzene measurements were conducted for the first time at four air monitoring sites in the Bangkok metropolitan region (BMR), from January to December 2001. Analytical results show that the mean benzene concentrations range from 42.4 micro g/m(3) at the Din Daeng urban site to 15.1 micro g/m(3) at the Chaeng Wattana suburban site. The monitoring results show that at a larger distance from the roadside or a higher level from the street surface, the level of benzene decreases. Analysis of the ambient benzene concentrations was carried out with reference to meteorological influences and traffic density. In traffic analysis, the combined effects of street topography and traffic flows established high impact on the overall benzene concentration in Bangkok. Statistical analysis shows good correlations of blood benzene levels and trans, trans-muconic acid with ambient benzene and demonstrated substantial exposure from traffic.

An environmental approach for used oil management in Asian cities: a Bangkok' s experience.

This paper addresses increasing concern about the pollution threat of used oil being illegally dumped and the impact of oil on air pollution and freshwater ecosystems in Asian countries. Used oil is a very serious waste management problem. These results call for management action such as maximising the collection and recovery of used oil. The Thai government recognizes the need to recycle used oil and has been active in encouraging programs to accomplish this goal. Thus unless new approaches and incentives are developed, used oil generation may become an increasing serious problem to our environment. The purpose of this study is to examine the technical and economic feasibility, of recycling used oils. In addition, this paper briefly discusses the problems to be overcome and outlines potential mechanisms for providing the necessary disposal controls in order to maximize the protection to public health and environmental quality from potential hazards posed by used lube oil disposal.

Environmental applicability of chitosan and zeolite for amending sewage sludge.

This study investigated the potential leachability of toxic heavy metals and pathogenic reduction in sewage sludge using chitosan and zeolite as adsorbing materials. Experiments were conducted on chitosan-sludge and zeolite-sludge mixtures in the application ratio of 0.1:10, 0.5:10, 1.0:10, 2.0:10, 3.0:10, and 4.0:10, respectively, and examined their capacities to bind some heavy metals (Zn, Cu, Ni and Pb) deriving from sewage sludge. Acrylic columns packed with chitosan and zeolite-sewage sludge mixtures in optimum ratio 1.0:10 and 3.0:10, respectively, were leached with tap water and sewage effluent at different pH levels. Seven eluate fractions were collected from the leaching test at leachant/dry sludge (L/S) ratio fixed to 0.48, 0.95, 1.43, 1.90, 2.38, 2.85, and 3.33 L/kg, respectively, and monitored for heavy metal and fecal coliform reductions. Results from leaching test studies for amended sludge showed that the variation of the observed heavy metal contents were influenced by the pH and eluate fractions of leachants. It was found that from neutral to acid conditions, the mobility of heavy metals in amended sludge mixtures was increased with the decrement of pH value in leachants. Zeolite-sludge was found to have higher percentage of reduced metal bioavailability than chitosan-sludge. It can be seen in column studies, pathogenic reduction in amended sludge mixtures were dependent with eluate fractions and type of amended materials. It was also revealed that chitosan can reduce greater fecal coliform counts in sewage sludge than that of zeolite.

The benefits and risks of using river sediment for Vietnamese agriculture: a case study of the Nhieu Loc canal in Ho Chi Minh City.

This study was conducted to assess the potential of river sediment for amendment of agricultural land with respect to heavy metal mobilization. The mobility and concentration of bioavailable heavy metal containing in the sediment were evaluated with the use of DTPA (diethylenetriamine pentaacetic acid) extraction techniques. Sum of metals in exchangeable and carbonate fractions obtained from sequential extraction scheme was used to evaluate the potential plant available. Four land blocks of size (1 m x 5.8 m) were prepared for cabbage field experiment and applied with different loading rates of sediment (approximately 28 and 42 ton/ha or equivalent to 100 kgN/ha and 150 kgN/ha). In parallel test, land blocks treated with fertilizer at similar nitrogen loading rates were also conducted for comparisons. Pure soil plot was used as a control system. Results show that both plant available and total heavy metal concentration were found higher in those plots treated with higher loading rates of sediment (42 ton/ha). The concentrations of heavy metals (Cu,Zn,Pb) in soil were decreased with time after crop harvesting and the residues remain in the soil were well below those of the UK, USA and Germany standards. Simple linear regression was used to show the correlation between the DTPA extractable metals and the plant metals fractions (root and shoot) resulting from fertilizer and sediment applications in the amended soils. In most cases, plant available metal concentrations showed positively correlated with plant metal uptake concentrations (R2 = 0.01-0.95, n = 3). Concentration of metals in the cabbage tissue detected: Zn at 131.53+/-10.43 mg kg(-1) DM, Cu at 20.84+/-1.62 mg kg(-1) DM, Pb at 0.09+/-0.01 mg kg(-1) DM, Cd at 0.21+/-0.09 mg kg(-1) DM and Ni at 0.44+/-0.05 mg kg(-1) DM. None of these metals concentration exceeded the tolerable limits of plant. One-way analysis of variance (ANOVA) was applied to find out the effect of different soil amendments on cabbage yield in term of fresh and dry weights. The sequence of crop yields in this field studies for amended soils is chemical fertilizer > sediment > control soil.

Assessment of treatment alternatives for laboratory cod wastewater: a practical comparison with emphasis on cost and performance.

This study focused on investigation of treatment alternatives for COD wastewater from academic laboratories, using a number of technologies including chemical reduction/precipitation, ion exchange and adsorption by chitosan. Results showed that high concentrations of 375 mg l(-1) chromium, 1,740 mg l(-1) mercury and 993 mg l(-1) silver in COD wastewater can be reduced to 2.34 mg l(-1), 3.65 mg l(-1) and 1.89 mg l(-1) respectively, by the chemical reduction/precipitation process. Results from ion exchange at a flowrate of 20 ml min(-1) showed breakthrough effluent concentrations obtained at 0.59 mg l(-1) chromium, 3.92 microg l(-1) mercury and 0.65 mg l(-1) silver corresponding to 75.6 l at 63 hr, 40.8 l at 34 hr and 33.6 l at 28 hr respectively. Kinetic and isotherm studies revealed that chitosan can adsorb Cr6+, Hg2+ and Ag+ ions most effectively at a flowrate of 20 ml min(-1) and the optimum pH for feed solution is 4. Chitosan column experiments indicated that average effluent concentrations at breakthrough point for chromium, mercury and silver are 0.76 mg l(-1), 6.04 mg l(-1) and 0.51 mg l(-1) respectively with throughput volumes and retention times of 120 l at 100 hr, 60 l at 50 hr and 48 l at 40 hr. Results of solidification experiments for chemical sludge and residual chitosan based on compressive strength and metal leachability tests showed, that the acceptable ranges of the solidification parameters were: sludge/cement = 0.1-1.0 (weight/weight), water/cement = 0.5-0.6 (weight/weight) and sand/cement = 0.5-3.0 (weight/weight). Operating cost per litre of COD wastewater treated, based on the current prices in Thailand was found to be Baht 19.95 for the chemical reduction/precipitation process, Baht 96.35 for ion exchange treatment and Baht 18.29 for chitosan adsorption.

An environmentally sound method for disposal of both ash and sludge wastes by mixing with soil: a case study of Bangkok plain.

This study reported the test done on ash-sludge mixture for amendment of soil in pot experiments. Ash-sludge mixture ratio studies revealed that 1:5 fly ash-sludge mixture and 1:10 bottom ash-sludge mixture were the optimum mixture ratio that minimized toxic element and provided sufficient nutrients. Experiments indicated that ash-sludge mixtures is more suitable for amendment of acid soil than neutral soil which can increase soil pH and reduce available heavy metal toxicity. The maximum heavy metal adsorption occurred in a pH range of 4 to 6 for all soil studied. The finding also revealed that fly ash application seemed more effective than bottom ash, due to its higher loading rate and metal contents. Heavy metal toxicity was monitored using seed germination test. Marigold and tomato seeds were the two crops selected for this test. Seed germination test result shows that percentage of seed germination increased in pot experiments with sludge only and ash-sludge mixtures. In addition, higher percentages of seed germination were observed to vary with longer incubation time (1-8 weeks). After week 12 of the incubation period, percentage of seed germination began to decline, as a result of reduced soil pH and release of toxic heavy metals.