Min-Pei Ling

Lung cancer risk in relation to traffic-related nano/ultrafine particle-bound PAHs exposure: A preliminary probabilistic assessment

Exposures to carcinogenic polycyclic aromatic hydrocarbons (PAHs) have been linked to human lung cancer. The purpose of this study was to assess lung cancer risk caused by inhalation exposure to nano/ultrafine particle-bound PAHs at the population level in Taiwan appraised with recent published data. A human respiratory tract model was linked with a physiologically based pharmacokinetic model to estimate deposition fraction and internal organic-specific PAHs doses. A probabilistic risk assessment framework was developed to estimate potential lung cancer risk. We reanalyzed particle size distribution, total-PAHs, particle-bound benzo(a)pyrene (B[a]P) and PM concentrations. A dose-response profile describing the relationships between external B[a]P concentration and lung cancer risk response was constructed based on population attributable fraction (PAF). We found that 90% probability lung cancer risks ranged from 10(-5) to 10(-4) for traffic-related nano and ultrafine particle-bound PAHs, indicating a potential lung cancer risk. The particle size-specific PAF-based excess annual lung cancer incidence rate due to PAHs exposure was estimated to be less than 1 per 100,000 population, indicating a mild risk factor for lung cancer. We concluded that probabilistic risk assessment linked PAF for limiting cumulative PAHs emissions to reduce lung cancer risk plays a prominent role in future government risk assessment program.

Assessing the potential exposure risk and control for airborne titanium dioxide and carbon black nanoparticles in the workplace

PurposeThis study assessed the potential exposure risks for workers in the workplace exposed to airborne titanium dioxide nanoparticles (TiO2-NPs) and carbon black nanoparticles (CB-NPs). The risk management control strategies were also developed for the NP engineering workplace.MethodsThe method used in this study was based on the integrated multiple-path particle dosimetry model to estimate the cumulative dose of nanoparticles (NPs) in the human lung. The study then analyzed toxicological effects such as pulmonary cytotoxicity and inflammation and evaluated the health risk associated with exposure to NPs in the workplace. Risk control measures such as the use of ventilating systems and N95 respirator protection are also discussed.Results and discussionThis study found that: (1) the cumulative dose of CB-NPs was greater than that of TiO2-NPs in human lungs; (2) there is a potential health risk to workers exposed to TiO2-NPs and CB-NPs in the absence of control measures in the workplace, with higher health risks associated with CB-NPs than TiO2-NPs; and (3) the use of a ventilating system and an N95 respirator offers greater protection in the workplace and significantly reduces the health risks associated with NP exposure.ConclusionThe present risk management control strategy suggests that the most effective way to reduce airborne NPs is to incorporate the use of a ventilating system combined with N95 respirator protection. This will enable the concentrations of TiO2-NPs and CB-NPs to be reduced to acceptable exposure levels.

Assessing trends and predictors of tuberculosis in Taiwan

BackgroundVariety of environmental and individual factors can cause tuberculosis (TB) incidence change. The purpose of this study was to assess the characteristics of TB trends in the period 2004 - 2008 in Taiwan by month, year, gender, age, temperature, seasonality, and aborigines.MethodsThe generalized regression models were used to examine the potential predictors for the monthly TB incidence in regional and national scales.ResultsWe found that (i) in Taiwan the average TB incidence was 68 per 100,000 population with mortality rate of 0.036 person-1 yr-1, (ii) the highest TB incidence rate was found in eastern Taiwan (116 per 100,000 population) with the largest proportion of TB relapse cases (8.17%), (iii) seasonality, aborigines, gender, and age had a consistent and dominant role in constructing TB incidence patterns in Taiwan, and (iv) gender, time trend, and 2-month lag maximum temperature showed strong association with TB trends in aboriginal subpopulations.ConclusionsThe proposed Poisson regression model is capable of forecasting patterns of TB incidence at regional and national scales. This study suggested that assessment of TB trends in eastern Taiwan presents an important opportunity for understanding the time-series dynamics and control of TB infections, given that this is the typical host demography in regions where these infections remain major public health problems.

Assessing the potential risks to zebrafish posed by environmentally relevant copper and silver nanoparticles.

The manufacture of large quantities of engineered nanomaterials (NMs) may lead to unintended contamination of aquatic ecosystems. Biologically based monitoring techniques need to be developed to detect these emerging NMs. The purpose of this study was to develop a risk-based probability model to predict the potential hazards of nanoecotoxicity toward aquatic organisms posed by waterborne copper and silver nanoparticles (Cu/Ag NPs). Published experimental evidence based on Cu/Ag NP-zebrafish (Danio rerio) systems was adopted as the study data. A Hill model was used to reconstruct a concentration-mortality response profile. A cumulative Weibull predictive model was employed to estimate exposure thresholds. The derived probabilistic model can predict the potential risk of environmentally relevant Cu/Ag NPs for major Taiwanese rivers with predicted environmental concentrations of 0.06 (95% confidence interval (CI): 0.01-0.92) mgL(-1) for Cu NPs and 0.04 (0.01-0.11) mgL(-1) for Ag NPs. The results indicated that estimated thresholds were 0.10-0.48mgL(-1) (95% CI) for Cu NPs and 2.69-2.73mgL(-1) for Ag NPs. The probabilities of a risk quotient (RQ) of >1 ranged 17%-81% for zebrafish exposed to Cu NPs. This study found that Ag NP exposure scenarios posed no significant risks to zebrafish (RQ≪0.1).

Risk management strategy to increase the safety of workers in the nanomaterials industry.

In recent years, many engineered nanomaterials (NMs) have been produced, but increasing research has revealed that these may have toxicities far greater than conventional materials and cause significant adverse health effects. At present, there is insufficient data to determine the permissible concentrations of NMs in the workplace. There is also a lack of toxicity data and environmental monitoring results relating to complete health risk assessment. In view of this, we believe that workers in the NMs industry should be provided with simple and practical risk management strategy to ensure occupational health and safety. In this study, we developed a risk management strategy based on the precautionary risk management (PRM). The risk of the engineered NMs manufacturing plants can be divided into three levels based on aspect identification, solubility tests, dermal absorption, and cytotoxic analyses. The risk management strategies include aspects relating to technology control, engineering control, personal protective equipment, and monitoring of the working environment for each level. Here we report the first case in which a simple and practical risk management strategy applying in specific engineered NMs manufacturing plants. We are confident that our risk management strategy can be effectively reduced engineered NM industries risks for workers.

Probabilistic framework for assessing the arsenic exposure risk from cooked fish consumption

Geogenic arsenic (As) contamination of groundwater is a major ecological and human health problem in southwestern and northeastern coastal areas of Taiwan. Here, we present a probabilistic framework for assessing the human health risks from consuming raw and cooked fish that were cultured in groundwater As-contaminated ponds in Taiwan by linking a physiologically based pharmacokinetics model and a Weibull dose–response model. Results indicate that As levels in baked, fried, and grilled fish were higher than those of raw fish. Frying resulted in the greatest increase in As concentration, followed by grilling, with baking affecting the As concentration the least. Simulation results show that, following consumption of baked As-contaminated fish, the health risk to humans is <10−6 excess bladder cancer risk level for lifetime exposure; as the incidence ratios of liver and lung cancers are generally acceptable at risk ranging from 10−6 to 10−4, the consumption of baked As-contaminated fish is unlikely to pose a significant risk to human health. However, contaminated fish cooked by frying resulted in significant health risks, showing the highest cumulative incidence ratios of liver cancer. We also show that males have higher cumulative incidence ratio of liver cancer than females. We found that although cooking resulted in an increase for As levels in As-contaminated fish, the risk to human health of consuming baked fish is nevertheless acceptable. We suggest the adoption of baking as a cooking method and warn against frying As-contaminated fish. We conclude that the concentration of contaminants after cooking should be taken into consideration when assessing the risk to human health.

A Probabilistic Transmission and Population Dynamic Model to Assess Tuberculosis Infection Risk

The purpose of this study was to examine tuberculosis (TB) population dynamics and to assess potential infection risk in Taiwan. A well-established mathematical model of TB transmission built on previous models was adopted to study the potential impact of TB transmission. A probabilistic risk model was also developed to estimate site-specific risks of developing disease soon after recent primary infection, exogenous reinfection, or through endogenous reactivation (latently infected TB) among Taiwan regions. Here, we showed that the proportion of endogenous reactivation (53-67%) was larger than that of exogenous reinfection (32-47%). Our simulations showed that as epidemic reaches a steady state, age distribution of cases would finally shift toward older age groups dominated by latently infected TB cases as a result of endogenous reactivation. A comparison of age-weighted TB incidence data with our model simulation output with 95% credible intervals revealed that the predictions were in an apparent agreement with observed data. The median value of overall basic reproduction number (R₀) in eastern Taiwan ranged from 1.65 to 1.72, whereas northern Taiwan had the lowest R₀ estimate of 1.50. We found that total TB incidences in eastern Taiwan had 25-27% probabilities of total proportion of infected population exceeding 90%, whereas there were 36-66% probabilities having exceeded 20% of total proportion of infected population attributed to latently infected TB. We suggested that our Taiwan-based analysis can be extended to the context of developing countries, where TB remains a substantial cause of elderly morbidity and mortality.

Mixture risk assessment due to ingestion of arsenic, copper, and zinc from milkfish farmed in contaminated coastal areas

Human health risks associated with the consumption of metal-contaminated fish over extended periods have become a concern particularly in Taiwan, where fish is consumed on a large scale. This study applied the interaction-based hazard index (HI) to assess the mixture health risks for fishers and non-fishers who consume the arsenic (As), copper (Cu), and zinc (Zn) contaminated milkfish from As-contaminated coastal areas in Taiwan, taking into account joint toxic actions and potential toxic interactions. We showed that the interactions of As–Zn and Cu–Zn were antagonistic, whereas As–Cu interaction was additive. We found that HI estimates without interactions considered were 1.3–1.6 times higher than interactive HIs. Probability distributions of HI estimates for non-fishers were less than 1, whereas all 97.5%-tile HI estimates for fishers were >1. Analytical results revealed that the level of inorganic As in milkfish was the main contributor to HIs, indicating a health risk posed to consumers of fish farmed in As-contaminated areas. However, we found that Zn supplementation could significantly decrease As-induced risk of hematological effect by activating a Zn-dependent enzyme. In order to improve the accuracy of health risk due to exposure to multiple metals, further toxicological data, regular environmental monitoring, dietary survey, and refinement approaches for interactive risk assessment are warranted.

Response to “Letter to Editor: Inappropriate exposure data and misleading calculations invalidate the estimates of health risk for airborne titanium dioxide and carbon black nanoparticle exposures in the workplace”

We thank Drs. Morfeld, McCunney, Levy, and Chaudhuri for their comments on our paper entitled “Assessing the potential exposure risk and control for airborne titanium dioxide and carbon black nanoparticles in the workplace” (Ling et al. 2011). Here we would like to provide some explanations. In our study, we have emphasized that the titanium dioxide nanoparticles (TiO2-NPs) exposure data adapted from TiO2-NPs manufacturing laboratory and carbon black nanoparticles (CB-NPs) exposure data most likely contribute from forklift and gas heater emissions in CB plant. Similarly, we also emphasized the cytotoxicity and inflammation experiment method might cause the difference between different species. However, based on very conservative assumptions, we assessed the potential exposure risk in order to protect workers. We would like to address some of the specific point about Morfeld et al. (2011) mentioned the main challenge for exposure data citation, dose–response study citation, and model uncertainty, respectively. 1 Exposure data citation

Response to "Dr. Luca Giannini's Letter to the Editor"

We thank Dr. Luca Giannini for his interest in our article and for his thoughtful comments. Here we would like to provide some explanations. In our study (Ling et al. 2011), we adopted the experimental data (Kuhlbusch et al. 2004) to reconstruct the carbon black (CB) nanoparticles (CB-NPs) concentration during propane forklift use in CB plants and assess the potential exposure risk in CB plants due to workers who may be exposed to part of CB-NPs. The CB-NPs exposure data of number size distributions were during forklift (propane fuel) operation near the sampling instrumentation. The number size distribution was increased in the particles size range 20−50 nm aerodynamic diameter as well as in the >1-μm particle size range. The particles in the nanoscale size range emission may be attributed to the forklift activity. Similarly, Wang et al. (2010) demonstrated that the CB-NPs size distributions for packaging, warehouse, and pelletizing area in CB manufacturing plant exposure were consistently in the form of bimodal. The first mode (count median diameter, 24.2−39.2 nm) could be contributed not only by the process emissions but also by the forklift exhaust or fugitive emissions of heaters, especially in the warehouse and pelletizing area. The second mode (count median diameter, 124−166 nm) was mainly from the CB-NPs emissions from the process areas. Wang et al. (2010) also emphasized that CB, forklift exhaust, and heater fugitive are carbon-containing materials; therefore, it is very difficult, if not impossible, to measure each individual concentration of these three pollutants. Even so, based on the very conservative assumptions in our study, we adopted the experimental data (Kuhlbusch et al. 2004) to assess the potential exposure risk in CB plants due to workers who may be exposed to part of CB-NPs in the bag filling areas in the CB plants. We deeply appreciate Dr. Luca Giannini for giving us an opportunity for clarifying the assumption in our study. The purpose of this study (Ling et al. 2011) was trying to assess the potential exposure risks for workers in the workplace exposed to airborne NPs and develop the risk management control strategies for the NP engineering workplace.