Exposure Routes and Health Risks Associated with Pesticide Application.

Pesticides play an important role in agricultural development. However, pesticide application can result in both acute and chronic human toxicities, and the adverse effects of pesticides on the environment and human health remain a serious problem. There is therefore a need to discuss the application methods for pesticides, the routes of pesticide exposure, and the health risks posed by pesticide application. The health problems related to pesticide application and exposure in developing countries are of particular concern. The purpose of this paper is to provide scientific information for policymakers in order to allow the development of proper pesticide application technics and methods to minimize pesticide exposure and the adverse health effects on both applicators and communities. Studies indicate that there are four main pesticide application methods, including hydraulic spraying, backpack spraying, basal trunk spraying, and aerial spraying. Pesticide application methods are mainly selected by considering the habits of target pests, the characteristics of target sites, and the properties of pesticides. Humans are directly exposed to pesticides in occupational, agricultural, and household activities and are indirectly exposed to pesticides via environmental media, including air, water, soil, and food. Human exposure to pesticides occurs mainly through dermal, oral, and respiratory routes. People who are directly and/or indirectly exposed to pesticides may contract acute toxicity effects and chronic diseases. Although no segment of the general population is completely protected against exposure to pesticides and their potentially serious health effects, a disproportionate burden is shouldered by people in developing countries. Both deterministic and probabilistic human health risk assessments have their advantages and disadvantages and both types of methods should be comprehensively implemented in research on exposure and human health risk assessment. Equipment for appropriate pesticide application is important for application efficiency to minimize the loss of spray solution as well as reduce pesticide residuals in the environment and adverse human health effects due to over-spraying and residues. Policymakers should implement various useful measures, such as integrated pest management (IPM) laws that prohibit the use of pesticides with high risks and the development of a national implementation plan (NIP) to reduce the adverse effects of pesticides on the environment and on human health.

Environmental monitoring and potential health risk assessment from Pymetrozine exposure among communities in typical rice-growing areas of China.

Pymetrozine is one of the most commonly used insecticides in China. This study was conducted to analyse Pymetrozine's potential exposures through various environmental routes beyond the treatment areas. The aim was to estimate the potential health risk for communities due to non-dietary exposures to Pymetrozine in soil and paddy water. Data on registration of pesticides in China, government reports, questionnaires, interviews and literature reviews as well as toxicological health investigations were evaluated to determine the hazard and dose-response characteristics of Pymetrozine. These were based on the US EPA exposure and human health risk assessment methods and exposure data from soil and paddy water samples collected between 10 and 20 m around the resident's location. The exposure doses from dermal contact through soil and paddy water were estimated. The potential cancer risk from the following exposure routes was evaluated: ingestion through soil; dermal contact exposure through soil; dermal contact exposure through paddy water. The potential total cancer risk for residents was estimated to be less than 1 × 10-6. These were relatively low and within the acceptable risk levels. The potential hazard quotient (HQ) from acute and lifetime exposure by dermal contact through paddy water and soil and acute and lifetime exposure by soil ingestion for residents was less than 1, indicating an acceptable risk level. This study suggested that there were negligible cancer risk and non-cancer risks based on ingestion and dermal contact routes of exposure to residents.

Corrigendum: Interdisciplinary Assessment of Hygiene Practices in Multiple Locations: Implications for COVID-19 Pandemic Preparedness in Vietnam.

[This corrects the article DOI: 10.3389/fpubh.2020.589183.].

Natural dynamics and residues of pymetrozine for typical rice-growing areas of China.

Pymetrozine has replaced toxic organophosphate pesticides previously used for controlling pests of rice crops in China. Existing data on its environmental behavior are usually related to studies on artificial plots that do not adequately address the natural dynamics and residues in actual field conditions. Therefore, studies under field conditions were carried out to investigate the natural dynamics and residues of pymetrozine in two typical rice-growing areas in China - Hunan and Guangxi provinces. Samples of paddy soil and water were collected in relation to spraying events in the study areas. The quick, easy, cheap, effective, rugged and safe (QuEChERS) method was used to extract pymetrozine residues from the samples by a Waters ACQUITY UPLC (Milford, MA, USA) system interfaced with a triple-quadrupole mass spectrometer (Xevo TQ-D, Waters Corp., USA). The initial deposition of pymetrozine in paddy soils was higher than in paddy waters in both areas. The decay of pymetrozine followed an exponential trend consistent with the first order kinetics. The half-life of pymetrozine in paddy water was determined to be 3.0 and 3.8 days, whereas the half-life in soil was 3.8 and 3.5 days in the Guangxi and Hunan samples, respectively. The decline rates of pymetrozine in paddy soil and paddy water in this field study were faster than those conducted under non-field conditions reported in previous studies. Compared to other pesticides used in China as reported in previous studies, the environmental persistence of pymetrozine in both paddy water and soils in Guangxi and Hunan provinces is very low. This has important implications for the use of pymetrozine in agricultural systems globally.

Smartphone Use and Willingness to Pay for HIV Treatment-Assisted Smartphone Applications among HIV-Positive Patients in Urban Clinics of Vietnam.

This study aimed to examine the effectiveness of Human Immunodeficiency Virus (HIV)-assisted smartphone applications in the treatment of HIV/AIDS patients in Vietnam. A cross-sectional study was performed in two urban outpatient clinics in Hanoi from May to December 2019. A simple random sampling method and a structured questionnaire were used to recruit 495 eligible participants and to collect data. Multivariable modified Poisson regression and multivariable linear regression models were employed to investigate the factors associated with the willingness to pay (WTP) and amount of money patients were willing to pay. Approximately 82.8% of respondents were willing to pay for the hypothetical applications, with the mean amount the participants were willing to pay of Vietnam Dong (VND) 72,100/month. Marital status (separate/divorced/widow: Odds ratio (OR) = 1.28, 95% confidence interval (CI) = (1.09; 1.50) and having spouse/partner: OR = 1.18, 95% CI = (1.03; 1.36)) and using health services (OR = 1.03, 95% CI = (1.01; 1.04)) were positively associated with nominating they would be WTP for the app, whereas the duration of antiretroviral treatment (ART) (OR = 0.98, 95% CI = (0.96; 0.99)) had a negative association. The frequency of using health services (ß = 0.04, 95% CI = (-0.07; -0.01)) was negatively associated with the amount of WTP. High levels of WTP revealed the feasibility of implementing smartphone-based apps for HIV treatment. This study implied the necessity to consider a co-payment system to reach populations who were in need but where such applications may be unaffordable in lieu of other treatment-associated expenses. Developers also need to pay attention to privacy features to attract single people living with HIV/AIDS and additional measures to initiate people with a long duration on ART into using the applications.

Agriculture Development, Pesticide Application and Its Impact on the Environment.

Pesticides are indispensable in agricultural production. They have been used by farmers to control weeds and insects, and their remarkable increases in agricultural products have been reported. The increase in the world's population in the 20th century could not have been possible without a parallel increase in food production. About one-third of agricultural products are produced depending on the application of pesticides. Without the use of pesticides, there would be a 78% loss of fruit production, a 54% loss of vegetable production, and a 32% loss of cereal production. Therefore, pesticides play a critical role in reducing diseases and increasing crop yields worldwide. Thus, it is essential to discuss the agricultural development process; the historical perspective, types and specific uses of pesticides; and pesticide behavior, its contamination, and adverse effects on the natural environment. The review study indicates that agricultural development has a long history in many places around the world. The history of pesticide use can be divided into three periods of time. Pesticides are classified by different classification terms such as chemical classes, functional groups, modes of action, and toxicity. Pesticides are used to kill pests and control weeds using chemical ingredients; hence, they can also be toxic to other organisms, including birds, fish, beneficial insects, and non-target plants, as well as air, water, soil, and crops. Moreover, pesticide contamination moves away from the target plants, resulting in environmental pollution. Such chemical residues impact human health through environmental and food contamination. In addition, climate change-related factors also impact on pesticide application and result in increased pesticide usage and pesticide pollution. Therefore, this review will provide the scientific information necessary for pesticide application and management in the future.

Gaps in awareness of climate variability and its impacts on society among health professionals and community workers in Vietnam: Implications for COVID-19 and other epidemic response systems.

The study presents a cross-sectional analysis via a web-based survey to assess the awareness and experiences of Vietnamese health professionals and community workers on climate and epidemic changes and their impacts on society. Health professionals, medical students, and community workers were included in the survey. Factor analysis was used to explore the construct validity of measures, and Multivariable Tobit regression models were used to examine associated factors with awareness about climate and epidemic changes and impacts on society. Results showed that the awareness of participants about climate and epidemic changes was moderately-low, while the awareness about the impacts on society were moderately high. Community workers show higher awareness of climate and epidemic changes compared to health professionals. People working in provincial levels had a lower score (Coef. = -0.64, 95%CI = -1.19 to -0.09) than those working in central level. Compared to Northern participants, those living in Central and Southern regions have lower awareness scores regarding "Changes in weather and epidemics" and "Changes in the environment" compared to Northern people. The higher awareness about climate and epidemic changes were found to be correlated with the higher awareness of "Impacts on health, society and economy" and "Impact on individuals and families". Community workers scored lower in "Impact on individuals and families" compared to health professionals (Coef.-0.75; 95%CI = -1.34 to -0.16). This study emphasized the vulnerabilities of Vietnamese communities to epidemics and climate change. It suggests the involvements of intersectoral taskforces in the preparedness and responses to climate change and epidemics.

Feasibility of Intersectoral Collaboration in Epidemic Preparedness and Response at Grassroots Levels in the Threat of COVID-19 Pandemic in Vietnam.

To effectively control the COVID-19 (coronavirus disease 2019) outbreak in later stages in Vietnam requires addressing the existing gaps in the national health emergency framework, consolidate, and inform its structure, we conducted this study to evaluate the importance and collaborative mechanism between health and community service workers with intersectional organizations at grassroots levels in Vietnam. A cross-sectional, web-based survey was conducted from 12/2019 to 02/2020 on 581 participants (37 health workers, 473 medical students, and 71 community service workers). The snowball sampling technique was used to recruit participants. We used exploratory factor analysis to test the construct validity of the questionnaire measuring the perceived efficiency of involving community service workers in health care-related activities and Tobit models to examine its associated factors. The results showed the importance of local organizations in epidemic preparedness and response at grassroots levels, with scores ranging from 6.4 to 7.1, in which the Vietnam Youth Federation played the most important role (mean = 7.1, SD = 2.2). Of note, community service workers were viewed as performing well in health communication and education at agencies, schools, and other localities. Medical students perceived higher efficiency of involving community service workers in health care-related activities at grassroots levels as compared to health workers. We encourage the government to promote intersectoral collaboration in epidemic preparedness and response, giving attention to scale up throughout training as well as interdistrict and interprovincial governance mechanisms.

Evaluating Training Need for Epidemic Control in Three Metropolitans: Implications for COVID-19 Preparedness in Vietnam.

Upon the outbreak of the COVID-19 pandemic, countries worldwide face a critical shortage of human resources in the health sector. Medical students are a potential task force with the capability to support the stretched health sector. This study aims to evaluate their training need for epidemic control in order to employ them effectively. A cross-sectional study was conducted using a web-based survey from December 2019 to February 2020. There were 5,786 observations collected using the snowball sampling technique. Logistic regression was applied to identify factors associated with training participation in epidemic prevention and disaster prevention. Multiple Poisson regression model was constructed to examine factors associated with the number of times they participated in sanitation training and disaster prevention activities in the previous 12 months. Sanitation and health education communication activities had the highest proportion of participants, with 76.5 and 38.4%, followed by examining and treating diseases in the community (13.4%). Those who participated in community activities had a higher number of times to participate in epidemic sanitation training and be involved in disaster prevention. This study informed the need for training programs to prepare medical students for COVID-19 epidemic responses. The training curriculum should include both theoretical approaches and contextual approaches to achieve efficient epidemic control.

Coverage of Health Information by Different Sources in Communities: Implication for COVID-19 Epidemic Response.

Health personnel and community workers are at the front line of the COVID-19 emergency response and need to be equipped with adequate knowledge related to epidemics for an effective response. This study aimed to identify the coverage of COVID-19 health information via different sources accessed by health workers and community workers in Vietnam. A cross-sectional study using a web-based survey was carried out from January to February 2020 in Vietnam. Respondent-driven sampling (RDS) was used for recruiting participants. We utilized the exploratory factor analysis (EFA) to examine the construct validity of the questionnaire. A higher percentage of participants knew about "Clinical and pathogen characteristics of COVID-19", compared to "Regulations and policies related to COVID-19". The percentage of participants accessing the information on "Guidelines and policies on prevention and control of COVID-19" was the lowest, especially among medical students. "Mass media and peer-educators" channels had a higher score of accessing COVID-19 information, compared to "Organizations/ agencies/ associations" sources. Participants consumed most of their COVID-19 information via "Internet, online newspapers, social networks". Our findings indicate an urgency to re-design training programs and communication activities for a more effective dissemination of information related to the COVID-19 epidemic or epidemics in general.

Interdisciplinary Assessment of Hygiene Practices in Multiple Locations: Implications for COVID-19 Pandemic Preparedness in Vietnam.

Due to the shared border with China, Vietnam faced risks from the COVID-19 pandemic at the early stages of the outbreak. Good hygiene practices were considered an effective prevention method, but there were only minimal data on the effectiveness of hygiene practices against the pandemic at the community level. Thus, this study aims to assess hygiene practices in society by using a community-based survey. A cross-sectional study using survey monkey was conducted from December 2019 to February 2020. The Snowball sampling technique was used to recruit participants and exploratory factor analysis was applied to scrutinize the construct validity of the measurement. We used the Tobit regression model to assess the association. Hygiene in a high-risk environment and hygiene in the social and educational environment were two main factors after applying the EFA method. Participants grade community sanitation quite low (around 6 out of 10). Furthermore, the mean score of hygiene practice at a local level in a high-risk environment was slightly low at 6.0. The score of sanitation in the Central region (5.3) was quite low compared to the North (5.8) and the South (6.2). The most high-risk environment was construction, industrial zone and food safety. Moreover, younger respondents were more likely to report poorer hygiene practices in high-risk environments (Coefficient = -1.67; 95% CI = -3.03; -0.32) and social and educational environment (Coefficient = -1.29; 95% CI = -2.54; -0.04). Our study gives an insight into pandemic preparedness at the grassroots level. The findings suggest the necessity of specific communication education for society to improve the compliance of hygiene practices to prevent the spreading of COVID-19.

Difference of trace element exposed routes and their health risks between agriculture and pastoral areas in Bay County Xinjiang, China.

The concentration level related to toxicities of trace elements in drinking water, rice, wheat flour, and their associated negative impacts on human health have become an emergent issue in China. Because Xinjiang is the largest province in China with the majority of arable pasture land available for cultivation, it is important to analyze the concentrations of trace elements in relation to their toxicities in water, rice, and wheat flour and to investigate the health risk differences between agricultural and pastoral areas in Bay County, Xinjiang. The study results showed that (1) metal concentrations from drinking water, rice, and wheat flour were within the permissible limits; (2) concentration levels of trace elements and their total risk from drinking water and rice were higher in the agricultural areas than those in the pastoral areas, whereas concentration levels of trace elements and their total risk from wheat flour were higher in the pastoral areas than those in the agricultural areas; (3) the concentration level of the trace elements in rice were higher than in the wheat flour, but the risk from the wheat flour was higher than the risk from rice; (4) total non-cancer risk from the flour (HIf) in both areas exceeded the respective safe reference doses; (5) total cancer risk from the wheat flour, rice, and water exceeded the safety limit (1 × 10-4); (6) for the exposed population, arsenic was suggested as the most evident pollutant leading to carcinogenic concerns regarding the water, rice, and wheat flour; (7) the risk index from the wheat flour made up the highest percentage both in the total cancer risk and the non-cancer risk, followed by rice and then water; and (8) the human health risk was attributed to influence from the local environment in the agriculture areas, while it was attributed to the external environment in the pastoral areas. Graphical abstract.

Comparative evaluation of chlorpyrifos exposure estimates from whole-body dermal dosimetry and urinary trichloro-2-pyridinol (TCP) methods.

Chlorpyrifos is one of the most widely used organophosphate pesticides and has a record of adverse effects on applicators. Assessment of exposure to chlorpyrifos based on its urinary metabolite, 3,5,6-trichloro-2-pyridinol (TCP), is considered as the most accurate. However, urine sampling can be difficult, and the laboratory analytical procedures involved are complex and expensive. A simpler approach for assessing pesticide exposure among applicators is the whole-body dermal dosimetry method, but this needs validation. The objective of this study was to compare chlorpyrifos exposure estimates obtained separately with the urinary TCP and the whole-body dermal dosimetry methods from applicators. Exposure estimates from the whole-body dermal dosimetry method (5-29 µg/kg/day) showed less variation than those from the urinary TCP method (1-71 µg/kg/day), but both were in close agreement at the mean level (16 µg/kg/day and 15 µg/kg/day, respectively). The whole-body dermal dosimetry method is therefore valid for providing estimates of the typical levels of pesticide exposure among applicators in situations where the urinary TCP method cannot be applied.

Biomonitoring of chlorpyrifos exposure and health risk assessment among applicators on rice farms in Ghana.

Chlorpyrifos is a neurotoxic insecticide that is widely used in the agricultural sector of Ghana. The main objective of this study was to evaluate the levels of chlorpyrifos exposure and health risk among applicators (n = 21) on irrigated rice farms in Ghana, based on a typical application event. Pre- and post-application urine samples (24-h) were collected from the applicators and analysed for 3,5,6-trichloro-2-pyridinol (TCP), using LC-MS/MS. The levels of chlorpyrifos-absorbed dose with the applicators were estimated from the urinary TCP levels. Prior to application, the median absorbed dose of chlorpyrifos (background exposure) with the applicators was 0.2 µg/kg/day (range 0.05 to 2 µg/kg/day). Following application, the median absorbed dose of chlorpyrifos (application exposure) increased 30-fold to 6 µg/kg/day (range 0.7 to 74 µg/kg/day). The mean elimination half-life (t1/2) of chlorpyrifos was calculated to be 50 h. Hazard quotient (HQ) values (HQ > 1) obtained with the chronic (10 µg/kg/day) and acute (100 µg/kg/day) guideline values of the WHO suggested no risk of chronic or acute health effects, respectively, among both the median and 5% highly exposed groups. However, HQ values (HQ > 1) obtained with the chronic (0.3 µg/kg/day) and acute (5 µg/kg/day) guideline values of the USEPA suggested risk of chronic and acute health effects, respectively, among both the median and 5% highly exposed groups. The quantity of chlorpyrifos formulation applied, spraying duration, and the number of spray tanks applied significantly correlated with the absorbed dose levels of chlorpyrifos from application exposure. Therefore, these factors suggest means to reduce exposure and consequent health risk among the applicators.

Health risk assessment of dermal exposure to chlorpyrifos among applicators on rice farms in Ghana.

Generally, there is limited information on pesticide absorbed dose levels and health risk attributable to the dermal route of exposure among applicators. The objective of this study was to evaluate the absorbed dose levels and consequent health risk from dermal exposure to chlorpyrifos among applicators on rice farms in Ghana. The whole-body dosimetry technique was used to capture chlorpyrifos residues penetrating the applicators' clothing and reaching their skin, as well as residues reaching uncovered body areas of the applicators. Acute (ADDD) and chronic (LADDD) absorbed dose levels of chlorpyrifos were estimated from the residues and plotted as cumulative probability distributions. Health risk from chlorpyrifos exposure was characterized using the Hazard Quotient (HQ) technique. Three of the four acute exposure guideline values used in the study indicated that applicators, represented by the median-exposed (ADDD, 15 µg/kg/day) and the 5% - highly exposed (ADDD, 27 µg/kg/day) groups were at high risk of acute adverse health effects due to chlorpyrifos exposure, with HQ values ranging from 1.5 to 5 and 2.7 to 9, respectively. Regarding chronic adverse health effects, none of the guideline values suggested risk among the median-exposed group (LADDD, 0.3 µg/kg/day), with HQ values ranging from 0.03 to 1. However, two of the chronic exposure guideline values suggested that the 5%- highly exposed group (LADDD, 0.6 µg/kg/day) may be adversely affected, with HQ values ranging from 1.2 to 2. These findings highlight the importance of the dermal route as a major pesticide exposure pathway and suggest possible exposure minimization strategies.

Dermal exposure of applicators to chlorpyrifos on rice farms in Ghana.

Studies evaluating dermal exposure to pesticides among applicators in tropical countries have largely been conducted using the patch dosimetry and hand wiping/washing techniques. This study used the more accurate whole-body dosimetry technique to evaluate dermal exposure to chlorpyrifos among applicators on rice farms in Ghana. The exposure levels were plotted as Cumulative Probability Distribution (CPD). Total Dermal Exposure (TDE) of chlorpyrifos among the median exposed and the 5% highly exposed groups during a spray event were 24 mg and 48 mg, respectively. When these were converted as a percentage of the quantity of active ingredient applied (Unit Exposure, UE), UE values of 0.03% and 0.06% were found among the median exposed and the 5% highly exposed groups, respectively. Overall, the hands were the most contaminated anatomical regions of the applicators, both in terms of proportion of TDE (39%) and skin loading (13 µg/cm2). Also, the lower anatomical region was more contaminated (82% of TDE) compared to the upper anatomical region (18% of TDE). The levels of chlorpyrifos TDE among the applicators were found to be influenced by the quantity of insecticide applied and the height of the crops sprayed (p < 0.05). The pesticide UE data of the present study can be used to estimate the levels of dermal exposure under similar pesticide use scenarios among applicators. The findings of the present study suggest that protecting the hands and the lower anatomical regions with appropriate PPE may significantly reduce exposure among applicators.

A new method for setting guidelines to protect human health from agricultural exposure by using chlorpyrifos as an example.

INTRODUCTION AND OBJECTIVES: Guidelines set by various agencies for the control and management of chlorpyrifos cover a wide range of values reflecting difficulties in the procedures for their development. To overcome these difficulties a new method to set guidelines would be developed. Published data derived from epidemiological investigations on human populations would be used to develop a dose-response relationship for chlorpyrifos allowing the calculation of threshold values which can be used as guidelines. MATERIALS AND METHOD: Data from the scientific literature on human populations were collected to evaluate the adverse response doses for a range of health effects. The Cumulative Frequency Distribution (CFD) for the minimum levels of adverse effects measured in terms of the Lifetime Average Daily Dose (LADD(D)) and the Absorbed Daily Dose for neurological (ADD(DN)) and non-neurological effects were used. RESULTS: Linear regression equations were fitted to the CFD plots giving R 2 values of 0.93 and 0.86 indicating a normal distribution of the data. Using these CFD plots, the chronic and acute threshold values were calculated at the 5% cumulative frequency level for chlorpyrifos exposure giving values at 0.5 µg/kg/d and 3 µg/kg/d respectively. CONCLUSIONS: Guidelines set using this technique at the values at 0.5 µg/kg/d and 3 µg/kg/d for chronic and acute exposure respectively provide an alternative to the currently used biological endpoint and safety factor method.

Needs assessment for reducing pesticide risk: a case study with farmers in Vietnam.

The objective of this study was to identify the needs for and solutions to pesticide risk reduction for farmers in Vietnam, using a comprehensive needs assessment model applied for evaluating community needs and policy development. Four kinds of needs were evaluated using qualitative research methods. A comparative analysis of pesticide regulations was used to identify comparative needs. In-depth interviews with authorities and experts were conducted to identify normative needs. Observations on farmer's practice were used to identify expressed needs, and focus group discussions among farmers were implemented to identify felt needs. The needs for pesticide regulations obtained from comparative analysis and experts include enhancement of pesticide legislation; multisectoral involvement in pesticide regulations; improvement of capacity for sectors involving in pesticide regulations; risk-benefit guidance for pesticide registration; reforms of pesticide regulations relating to the restriction, cancellation, suspension, transport, storage, and disposal of pesticides; and the development of occupational hygiene and safety policy and programs for agricultural activities. The expressed needs based on field observations comprise improvement in knowledge and behavior of farmers about pesticide safety with specific areas, and supports in safety facilities and personal protective equipment. The key request from farmers include needs about technical training for occupational safety and hygiene of pesticide application, and support for safety facilities for pesticide application and protective equipment. The results of comprehensive needs assessment were useful in the development of a range of strategies in legislative improvement, workplace and personal hygiene, information and training, and medical surveillance and pesticide poisoning first aids for pesticide risk reduction for Vietnamese farmers.

Volatile aromatic hydrocarbons (VAHs) in residential indoor air in Brisbane, Australia.

Volatile aromatic hydrocarbons (VAHs: benzene, toluene, ethylbenzene, mp-xylene, o-xylene, styrene, naphthalene) in residential indoor air in Brisbane, Australia were measured in 32 houses. The total VAHs (TVAHs) levels ranged between 2 and 137µg/m(3) and were lower than the most of the houses in the literature data. The VAHs were believed to originate from heat insulation systems, building material products as well motor vehicles but naphthalene and styrene originated from other sources. Internal garages had concentrations which are higher than the indoor air by 25-50% due to the presence of motor vehicles and may be a major source of indoor VAHs. However indoor concentrations are higher than that in the outdoor ambient air. The age of the house was found to be negatively related to VAHs concentrations in the houses with the half-life of TVAH at approximately 13years. The concentration levels of benzene, toluene, ethylbenzene and styrene are well below the guideline values set by agencies from Hong Kong, Japan, Germany and the WHO while the concentration level of naphthalene in one house exceeded the guideline value from Germany.

Health risk characterization of chlorpyrifos using epidemiological dose-response data and probabilistic techniques: a case study with rice farmers in Vietnam.

Various methods for risk characterization have been developed using probabilistic approaches. Data on Vietnamese farmers are available for the comparison of outcomes for risk characterization using different probabilistic methods. This article addresses the health risk characterization of chlorpyrifos using epidemiological dose-response data and probabilistic techniques obtained from a case study with rice farmers in Vietnam. Urine samples were collected from farmers and analyzed for trichloropyridinol (TCP), which was converted into absorbed daily dose of chlorpyrifos. Adverse health response doses due to chlorpyrifos exposure were collected from epidemiological studies to develop dose-adverse health response relationships. The health risk of chlorpyrifos was quantified using hazard quotient (HQ), Monte Carlo simulation (MCS), and overall risk probability (ORP) methods. With baseline (prior to pesticide spraying) and lifetime exposure levels (over a lifetime of pesticide spraying events), the HQ ranged from 0.06 to 7.1. The MCS method indicated less than 0.05% of the population would be affected while the ORP method indicated that less than 1.5% of the population would be adversely affected. With postapplication exposure levels, the HQ ranged from 1 to 32.5. The risk calculated by the MCS method was that 29% of the population would be affected, and the risk calculated by ORP method was 33%. The MCS and ORP methods have advantages in risk characterization due to use of the full distribution of data exposure as well as dose response, whereas HQ methods only used the exposure data distribution. These evaluations indicated that single-event spraying is likely to have adverse effects on Vietnamese rice farmers.