A total of 127 waste disposal sites in Thailand include landfills (88.19%), incinerator (2.63%), and integrated systems (9.45%), respectively. 85% of all landfills are presently operated and 50% of all located in the central part of Thailand. The most of waste disposal sites are disposed legally in landfills. Landfill is the end of disposal site to waste, intended to minimize the impact of solid waste on human health and environment [
In addition, exhaust fumes of waste collection trucks traveling to and from disposal sites, dust from disposal operations, and open burning of waste all contribute to occupational health problems [
Workers who worked in cleaning the precipitates had higher blood lead levels (16
The objective of this study was to determine and evaluate the level of blood cadmium and blood lead among subject workers exposed to cadmium and lead from behaviors in terms of their possible role in worker contamination and transfer of cadmium and lead to the body.
The study was designed as a cross-sectional study. Whole blood samples were collected from workers in five sanitary landfill areas in southern Thailand, between August and October 2014. This research was approved by the Ethics Committee of the Institute of Research and Development, Thaksin University.
The population in this study included the subject workers (30 office workers, 30 drivers, and 54 garbage workers, resp.) who work at sanitary landfill sites in southern Thailand. The landfill sites are located at 2 sites in Nakhon Si Thammarat province, 2 sites in Songkha province, and 1 site in Phatthalung province. Nakhon Si Thammarat province, Songkha province, and Phatthalung province are located in middle southern Thailand that presented the landfill area supporting the amount of solid waste in municipalities increasing every year (more than 1000 tons a day in 2015), and all of areas have an approximate area of more than 24,000 square kilometers. All of landfill was managed by Local Administrative Organization. The sampling was selected by purposive selection. All of subjects were formal workers. The formal workers who worked at 5 sanitary landfill areas were 456 persons to determine the sample size by using the 25 percent of the population. 100 percent of the subject workers (114 persons) agreed to participate in this study. The inclusion criteria for the subject workers were formal workers and of age 20–60 years, in occupational contact for at least one year. In this study, classification of risk exposure is in two groups including (1) direct group including the subject workers who work in the process of mixing domestic, transferring waste, sorting, and dumping at landfill; (2) indirect group including drivers and office workers. Questionnaire was used by interviewing in subject workers group. Face-to-face interview and walkthrough survey were used by collecting general information on the subject workers. From each sample, one aliquot (4 mL) was kept in an acid cleaned plastic test tube and was analyzed for cadmium and lead content with the GFASS [
In the questionnaire, information on the following variables was collected: general information, work characteristics (e.g., office workers, drivers, and garbage workers), and personal hygiene, as a result of managing sanitary landfill processes, which lasted three months. The patterns of behavior reported in the questionnaire were confirmed by directing observation. Whole blood was collected from the study participants at the end of their work shift.
Blood cadmium sample was transferred into 100 mL conical flash. The EDTA bottle was rinsed with little HNO3 and transferred into the 100 mL conical flash. Then, two mL perchloric acid and six mL nitric acid (1 : 3). The conical flash was covered with an evaporating dish. Next, the samples were mixtures digested at low temperature. The digest was made up to 20 mL with deionized water in a 20 mL standard flash. The measurement was made at 288.8 nm. Under the operation conditions were previously described in detail [
Graphite furnace atomic absorption spectrophotometer (GFASS), Hitachi Model Z-8200 (Hitachi Ltd., Tokyo, Japan), was used for measuring the blood cadmium levels and lead levels. Field water blank samples were frozen and shipped on dry ice in all of the analyses as a quality control. These field blanks of cadmium were analyzed by using the same method. Standard cadmium solution of 100 mg/L was prepared by dilution with 0.2% nitric acid from a stock solution of 1000 mg/L (Merch, FRG). A series standard of blood cadmium level was prepared at 2.5, 5.0, and 10.0
Blood lead sample preparation place 2 mL of whole blood into a culture tube. Start a reagent blank at this point with 2 mL deionized water and 0.8 mL of diluted solution (ammonium pyrrolidine dithiocarbamate) was added. The samples were mixed on a rotary vibration mixer for 10 seconds. Then, 2 mL of water saturated with methyl isobutyl ketone (MIBK) was added to the mixture. Each culture tube was capped and rotated on a rotary vibration mixer for 2 minutes. Next, the samples were centrifuged at 2,000 rpm for 10 minutes. Next, the samples were analyzed with lead ammonium pyrrolidine dithiocarbamate (Pb-APDC) solution in MIBK within 2 hours of extraction [
Whole blood lead determination was calibrated by preparing a series of standard additions, that is, 0, 5, 10, 20, 30, and 50
Descriptive statistics were used to present the blood cadmium levels and blood lead levels test results. The independent
One hundred and fourteen subjects participated in the present study. Most subjects (74.6%) were male and most subjects (57.9%) were aged between 35 and 44 years. Most subjects had secondary level and the mean income was 7,569 baht per month. Most subjects smoked cigarettes (56.1%) and drank alcoholic beverages (57.9%) (Table
General characteristics of the subject workers.
Parameter | Subject workers ( |
% |
---|---|---|
Gender | ||
Male | 85 | 74.6 |
Female | 29 | 25.4 |
Age (years) | ||
≥20–34 | 66 | 57.9 |
35–44 | 28 | 24.6 |
45–54 | 20 | 17.5 |
Education level | ||
Secondary school | 44 | 38.6 |
Vocational school | 37 | 32.5 |
Diploma degree or higher | 33 | 28.9 |
Income (Baht) | ||
<7500 | 76 | 66.7 |
≥7500 | 38 | 33.3 |
Smoked cigarettes | ||
Yes | 64 | 56.1 |
No | 50 | 43.9 |
Alcohol consumption | ||
Yes | 66 | 57.9 |
No | 48 | 42.1 |
Most subjects (85.1%) had been working for ≥10 years. Most subjects worked for >8 hours per day and 6 days per week, at 60.5 and 71.9%, respectively. Most subjects (47.4%) sorted general waste (Table
Work characteristic of the subject workers.
Parameter | Subject workers ( |
% |
---|---|---|
Position | ||
Office workers | 30 | 26.3 |
Drivers | 30 | 26.3 |
Garbage workers | 54 | 47.4 |
Duration of work (year) | ||
<10 | 17 | 14.9 |
≥10 | 97 | 85.1 |
Hours worked per day | ||
8 | 45 | 39.5 |
>8 | 69 | 60.5 |
Days worked per week | ||
6 | 82 | 71.9 |
>6 | 32 | 28.1 |
The majority (85.0%) started working at age < 15 years. 26.3% were drivers, 47.3% were garbage workers, and 26.3% worked in an office. Subject workers (25.4%) did not use a cotton mask to protect themselves from air pollutants, 64.0% of workers used gloves when collecting or handling waste, and 60.5% of workers used aprons when collecting waste.
Forty-six point four percent always ate snacks or drank water while working. Over half of the workers (58.8%) always washed their hands before lunch. Workers (20.5%) sometimes changed their clothes after worked. Before going home, none of the workers took a shower or regularly changed their clothes (Table
PPEs used and personal hygiene behaviors characteristic of the subject workers.
Parameter | Subject workers ( |
% |
---|---|---|
|
||
Cotton mask | ||
No | 29 | 25.4 |
Yes | 85 | 74.6 |
Gloves | ||
No | 73 | 64.0 |
Yes | 41 | 36.0 |
Aprons | ||
No | 45 | 39.5 |
Yes | 69 | 60.5 |
|
||
Ate snacks or drank water at work area | ||
Sometimes | 60 | 52.6 |
Always | 54 | 47.4 |
Washed hands before lunch | ||
Sometimes | 47 | 41.2 |
Always | 67 | 58.8 |
Changed clothes after work | ||
Sometimes | 72 | 63.2 |
Always | 42 | 36.8 |
Comparison of blood cadmium levels and blood lead levels in subject workers.
Parameter | Mean |
Range |
---|---|---|
Blood cadmium levels ( |
|
1.58–7.03 |
Blood lead levels ( |
|
1.98–11.12 |
It was found that the mean blood lead levels and blood cadmium levels and age, income, smoke cigarettes, duration of work, hours worked per day, days worked per week, work position, use of PPE (mask, gloves, and apron), eating snacks or drinking water during work, and washing hands before lunch were significantly different, at
Workers who had worked ≥10 years had significantly higher blood cadmium levels and blood lead levels than those who had worked <10 years (
The results indicated that the mean blood cadmium levels and blood lead levels among work positions were significantly different (
Variables related to subject workers’ blood cadmium levels and blood lead levels.
Parameter | Subject workers ( |
Blood cadmium levels ( |
95% CI |
|
Blood lead levels ( |
95% CI |
|
---|---|---|---|---|---|---|---|
Gender | |||||||
Male | 85 (74.6) | 1.96 |
1.59–2.11 | <0.001 |
8.57 |
2.25–2.89 | <0.001 |
Female | 29 (25.4) | 1.39 |
1.30–1.87 | 3.21 |
1.65–2.77 | ||
Age (years) | |||||||
≥20–34 | 66 (57.9) | 1.82 |
1.70–1.50 | 0.258 | 3.37 |
1.97–2.58 | 0.524 |
35–44 | 28 (24.6) | 1.65 |
1.27–2.04 | 3.70 |
1.93–3.27 | ||
45–54 | 20 (17.5) | 1.85 |
1.28–2.41 | 4.00 |
2.15–3.84 | ||
Education level | |||||||
Secondary school | 33 (28.9) | 1.53 |
1.15–1.90 | 0.412 | 4.79 |
2.15–3.42 | 0.127 |
Vocational school | 37 (32.5) | 1.83 |
1.46–2.19 | 3.96 |
2.05–3.08 | ||
Diploma degree or higher | 44 (38.6) | 1.93 |
1.58–2.29 | 4.38 |
1.83–3.53 | ||
Income (Baht) | |||||||
<7500 | 76 (66.7) | 1.54 |
1.64–2.17 | <0.001 |
2.63 |
2.21–2.89 | <0.001 |
≥7500 | 38 (33.3) | 2.00 |
1.21–1.86 | 7.55 |
1.85–4.83 | ||
Smoked cigarettes | |||||||
Yes | 50 (43.9) | 2.79 |
1.52–2.05 | <0.001 |
8.94 |
2.49–4.38 | <0.001 |
No | 64 (56.1) | 1.78 |
1.47–2.09 | 3.12 |
1.79–2.45 | ||
Alcohol consumption | |||||||
Yes | 66 (57.9) | 1.73 |
1.51–2.23 | 0.492 | 4.61 |
2.24–2.96 | 0.309 |
No | 48 (42.1) | 1.87 |
4.32 |
1.86–2.76 | |||
Position | |||||||
Office workers | 30 (26.3) | 1.40 |
1.22–1.58 | <0.001 |
4.45 |
2.04–2.85 | 0.001 |
Drivers | 30 (26.3) | 2.21 |
1.86–2.57 | 8.52 |
2.13–4.90 | ||
Garbage workers | 54 (47.4) | 4.05 |
2.10–0.58 | 10.58 |
1.90–4.28 | ||
Duration of work (year) | |||||||
<10 | 17 (14.9) | 1.15 |
0.85–1.46 | <0.001 |
3.05 |
1.39–2.72 | <0.001 |
≥10 | 97 (85.1) | 1.89 |
1.67–2.12 | 8.55 |
2.25–3.86 | ||
Hours worked per day | |||||||
8 | 45 (39.5) | 1.68 |
1.37–2.00 | 0.438 | 3.20 |
1.78–2.63 | <0.001 |
>8 | 69 (60.5) | 1.85 |
1.57–2.12 | 7.67 |
2.30–3.03 | ||
Days worked per week | |||||||
6 | 82 (71.9) | 1.70 |
1.45–1.94 | 0.188 | 4.28 |
1.98–4.57 | 0.001 |
>6 | 32 (28.1) | 2.00 |
1.61–2.40 | 8.01 |
2.38–3.63 | ||
|
|||||||
Cotton mask | |||||||
No | 29 (25.4) | 1.81 |
1.57–2.01 | <0.001 |
8.31 |
2.01–4.59 | <0.001 |
Yes | 85 (74.6) | 0.71 |
1.29–2.13 | 2.33 |
2.33–3.67 | ||
Gloves | |||||||
No | 73 (64.0) | 1.83 |
1.33–2.09 | <0.001 |
8.28 |
1.79–4.75 | <0.001 |
Yes | 41 (36.0) | 1.71 |
1.58–2.08 | 2.60 |
2.25–3.94 | ||
Aprons | |||||||
No | 45 (39.5) | 1.77 |
1.44–1.99 | 0.258 | 4.55 |
2.10–4.78 | 0.478 |
Yes | 69 (60.5) | 1.89 |
1.57–2.21 | 4.43 |
1.07–2.79 | ||
|
|||||||
Ate snacks or drank water at work area | |||||||
Sometimes | 60 (52.6) | 2.08 |
1.78–2.38 | <0.001 |
7.65 |
2.26–3.03 | <0.001 |
Always | 54 (47.4) | 1.06 |
1.18–1.73 | 2.30 |
1.89–2.70 | ||
Washed hands before lunch | |||||||
Sometimes | 47 (41.2) | 2.02 |
1.65–2.39 | <0.001 |
7.49 |
2.05–4.93 | <0.001 |
Always | 67 (58.8) | 1.02 |
1.38–1.87 | 4.49 |
2.11–3.84 | ||
Changed clothes after work | |||||||
Sometimes | 42 (36.8) | 1.98 |
1.61–2.35 | <0.001 |
8.54 |
2.08–4.91 | <0.001 |
Always | 72 (63.2) | 1.07 |
1.42–1.92 | 4.44 |
2.09–3.80 |
To predict the blood cadmium levels and blood lead levels of workers, a multiple regression model was constructed, as shown in Table
Multiple regression occupational life style, used PPE, and personal hygiene behavior on blood cadmium and lead levels in subject workers (
Dependent variable, independent variable | Blood cadmium levels in subject workers | Blood lead levels in subject workers | ||||||
---|---|---|---|---|---|---|---|---|
Adjusted |
Standardized beta coefficient |
|
Significance | Adjusted |
Standardized beta coefficient |
|
Significance | |
|
||||||||
Smoking | 0.418 | 0.341 | 4.213 | 0.001 |
0.450 | 0.452 | 4.402 | 0.001 |
Days worked per week | 0.432 | 4.521 | 0.001 |
0.021 | 0.112 | 0.743 | ||
Duration of work | 0.039 | 0.401 | 0.521 | 0.055 | 0.492 | 0.674 | ||
Position | 0.448 | 5.120 | 0.001 |
0.466 | 4.480 | 0.001 |
||
Mask |
|
|
0.001 |
|
|
0.001 |
||
|
||||||||
Smoking | 0.458 |
|
|
0.897 | 0.378 | 0.032 | 0.622 | 0.574 |
Days worked per week | 0.511 | 5.200 | 0.001 |
0.062 | 0.395 | 0.544 | ||
Duration of work | 0.095 | 0.897 | 0.450 | 0.118 | 1.850 | 0.095 | ||
Position | 0.158 | 2.058 | 0.312 | 0.395 | 3.801 | 0.001 |
||
Gloves |
|
|
0.031 |
|
|
0.011 |
||
|
||||||||
Smoking | 0.401 | 0.445 | 4.810 | 0.001 |
0.530 |
|
|
0.501 |
Days worked per week | 0.025 | 0.251 | 0.410 | 0.408 | 4.585 | 0.001 |
||
Duration of work | 0.075 | 0.870 | 0.390 | 0.382 | 3.854 | 0.001 |
||
Position | 0.091 | 0.955 | 0.420 | 0.145 | 1.452 | 0.148 | ||
Ate snacks or drank water at work |
|
|
0.001 |
0.565 |
|
0.021 |
||
|
||||||||
Smoking | 0.569 | 0.501 | 5.220 | 0.001 |
0.391 |
|
|
0.251 |
Days worked per week | 0.691 | 6.852 | 0.001 |
0.410 | 4.210 | 0.001 |
||
Duration of work | 0.051 | 0.511 | 0.721 | 0.382 | 3.791 | 0.001 |
||
Position | 0.495 | 5.233 | 0.001 |
0.325 | 3.180 | 0.001 |
||
Washed hands before lunch |
|
|
0.001 |
0.004 | 0.072 | 0.985 |
In equation 2, the entire
In equation 3, the entire
In equation 4, the entire
Blood cadmium level is an indicator of recent exposure although, upon long-term exposure (i.e., decades). The most commonly, blood levels was used maker for lead exposure and reflects a combination of exposure during the last month and several years back in time [
Alfvén et al. [
All subject workers had blood lead levels <30
A recent study found many factors influencing the increase of blood cadmium levels and blood lead levels. A result in this study shown that the mean of blood cadmium levels and blood lead levels were significantly different with different work position (such as that of garbage worker) and difference work duration [
The result of the present study was similar with Decharat [
In addition, a long time exposure of subject workers during worked may influence the levels of cadmium and lead in blood; accumulation of these metals can be occurring in the bodies due to a lack of practices a lack of appropriate prevention measures [
From what is observed in this study, PPE was used by subject workers, but type of PPE was inappropriate for this type of work. The pollutants of heavy metals can accumulate on the surface of PPE used by the subject workers such as cadmium and lead can accumulate on cotton mask, penetrate a cotton mask to inhalation pathway.
Because they were not aware of the need to clean and waited until the job was finished each day or more. With regard to PPE use, it was found that workers who used cotton mask, gloves, and aprons had significantly lower blood cadmium and blood lead levels than those who did not. Subject workers who had poor protective practices had a blood cadmium level up to 7.03
This subject worker was exposed to up to 7.03
Personal hygiene and behavioral risk factors were also associated with blood cadmium levels and blood lead levels. Subject workers who ate snacks during working had significantly higher blood cadmium levels and blood lead levels than those who did so sometimes. In addition, subject workers who washed their hands before the start of lunch had significantly lower blood cadmium levels and blood lead levels than those who did so sometimes. From what is observed in site area, no convenient washing facilities (with warm water and soap) were available near the collection point or work station in landfill site or for those working in the street. The result was similar to the study conducted by Rogers, 1983 [
From what is observed in the areas, the authors noted that 70% of subject workers got food from the workplace and found food in the dump site. In addition, 92% water supply was used for drinking during work, and 8% carried water from their home. This result is supported by Sunthonchai and Phoolpoksin [
Oyelola et al. [
In addition, the elevated lead exposure among subject workers is worrying, mainly for the women working in these settings. Children’s neurodevelopment can be occurring from prenatal lead exposure, as reported by several studies [
Significant predictors of blood cadmium levels and blood lead levels included smoked cigarettes. This result is supported by Julander et al. [
Results in this study that the health risk behaviors of occupational life style, used PPE, and personal hygiene may endanger the health of the subject workers. Wearing of internationally recommended personal protective dressing [
The author declares that there is no conflict of interests regarding the publication of this paper.
The author would like to thank subject workers at the five sanitary landfill areas for enabling collection of whole blood samples. The author would also like to thank the staff of the Central Equipment Unit, Faculty of Medicine Technology, Mahidol University, for their assistance in sample analysis. This research was supported by the Research and Development Institute, Thaksin University (RDITSU).