Jimmy Yu

Public Health Risks from Heavy Metals and Metalloids Present in Traditional Chinese Medicines

Out of 247 traditional Chinese medicines (TCM) investigated, a proportion were contaminated with arsenic (5–15%), lead (∼5%), and mercury (∼65%). Some preparations exceeded the tolerable daily intake (TDI) for males and females for arsenic (4 and 5 products, respectively), lead (1 and 2 products), and mercury (5 and 7 products). These exceedances were as high as 2760-fold, which posed a potential danger to public health. As many users are known to self-prescribe, there is a substantial risk of poisoning from the consumption of these contaminated TCM.

Importance of Internal Biotic Concentrations in Risk Evaluations with Aquatic Systems

Ecological risk evaluations are commonly performed using aqueous concentrations and aqueous toxicity measurements as a starting point. However risk evaluations could be carried out using internal biotic concentrations and the internal lethal or sublethal concentrations. This has several advantages. Firstly, the internal lethal and sublethal concentrations are relatively consistent in groups of chemicals having a similar mode of action. Thus in field situations the internal concentration, in fish and possibly other biota, can be used to evaluate possible biotic effects. Also other histopathological, biochemical, biomolecular and physiological effects can be assessed and used with this information to give an overall assessment. There are, however, several limitations with this approach including sensitivity, health, age and nutritional status of the biota as well as a lack of data on dose/response relationships with internal concentrations.

Health Risk Assessment of Chlorobenzenes in the Air of Residential Houses Using Probabilistic Techniques

A human health risk assessment was performed to evaluate the risks due to chlorobenzenes in the air of residential houses. Chlorobenzenes found in the air in the toilets, rooms, and outdoors of three houses in Brisbane, Australia, were sampled by trapping on Tenax TA and analyzed using an automated thermal desorption (ATD)–gas chromatography/mass spectrometry (GC/MS) method. Concentrations of 1,4-dichlorobenzene (1,4-DCB) in the rooms, toilets, and outdoors were used as the exposure concentrations (E), while those in the toilets (μg/m3) were used as the high-exposure concentrations (HE). The exposure concentrations were transformed into exposure doses (EXDE and EXDHE). Dose-response data from the literature for a range of adverse effects in animals were obtained and exposure doses were expressed as human equivalent dose (HED). The HED values were higher than the EXDE and EXDHE values for all adverse effects, and a hazard quotient was calculated that indicated a low level of risk with the high-exposure environment. The lifetime average daily doses (LADDs) for a wide range of adverse effects observed in human case studies were estimated and compared to the doses in the high-exposure (HE) situation. Using the Monte Carlo simulation technique the probabilities of risk quotients higher than unity ranged from 0.02 to 0.26. This evaluation indicated that 1,4-DCB posed low risks to general residents; however, for individuals with susceptible characteristics and exposure to elevated 1,4-DCB, the probability of adverse responses was moderate to high.

Extraction and HPLC Characterization of Chlorogenic Acid from Tobacco Residues

Abstract Chlorogenic acid is a highly valuable natural polyphenol compound used in medicine and industries. Its current commercial sources are from plant extracts of Lonicera japonica Thunb and Eucommia ulmoides Oliver. These sources are limited and expensive. On the other hand, tobacco residuals contain chlorogenic acid and other natural polyphenol compounds. Large quantities of tobacco residuals are produced each year as waste materials from tobacco manufacturing, potentially providing an alternative commercial source of chlorogenic acid and other valuable compounds. In this paper, microwave and ultrasound extractions of chlorogenic acid with mixed solvent were studied. Total polyphenol concentrations in extract solutions obtained with different extraction methods were analyzed with the method of ferrous tartrate and UV‐Vis spectrophotometry and compared. The extraction solutions were also characterized for polyphenol compositions with the method of HPLC. Experimental results indicated that high extract concentrations of chlorogenic acid were obtained with a mixed solvent of acetone and water (1:2 v/v). A total polyphenol concentration of up to 4.87 mg/ml and a chlorogenic acid concentration of up to 2.12 mg/ml were achieved. The application of microwave and ultrasound significantly increased the extract concentrations. The extraction time needed was also much reduced. HPLC analysis indicated that acetone water mixed solvent extraction achieved much higher relative concentrations of chlorogenic acid to other compounds in the extract solutions. These results indicted that fast and effective extraction of chlorogenic acid from tobacco residuals were achieved.

Use of exposure time and life expectancy in models for toxicity to aquatic organisms

The exposure time is a variable which is usually not incorporated into models for toxicity. However, with persistent organic pollutants (POPs) exhibiting a nonspecific mode of action and lipophilic properties this variable can be modeled by the usage of the internal concentrations as a measure of the toxicity with fish. The bioconcentration process with fish is a relatively well understood and predictable process which allows the calculation of the internal lethal concentration. When the exposure time is relatively short the critical internal lethal concentrations are relatively constant for the group of POPs whereaas the LC50 measured in the ambient water is quite variable. When the exposure time is relatively long, results on the measurement of the critical internal concentration with fish over different exposure times has demonstrated that the internal lethal concentration falls with increasing exposure times in a consistent and predictable manner. This reduction in life expectancy can be described in a model which can be used to estimate the critical internal concentration for any exposure time. It also provides information useful in assessing the risk to fish and potentially other species due to the occurrence of residues of POPs in natural aquatic systems. It is suggested that these relationships can be extended to other groups of organisms and chemicals.

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.

DESORPTION OF Cu2+ FROM A BIOSORBENT DERIVED FROM THE MARINE ALGA DURVILLAEA POTATORUM

The desorption and recovery of Cu2+ from a biosorbent material derived from marine alga Durvillaea potatorum were studied. The biosorbent was a pretreated biomass of Durvillaea potatorum with calcium chloride solution and thermal treatment. The Cu2+ was adsorbed onto the biosorbent and then desorbed by various elution solutions. Batch desorption tests established a solution of 0.35 M hydrochloric acid as the most appropriate eluting agent. Fixed-bed desorption recovery curves for Cu2+ were also obtained. In addition, batch desorption recovery curves for Cu2+ were obtained for multiple consecutive adsorption–desorption cycles and the biosorption properties of the biomass for Cu2+ were compared after the fifth cycle to evaluate the stability of the biomass. The use of a mixture of 0.35 M hydrochloric acid and 0.5 M calcium chloride as the eluting agent improved the stability of the biosorbent in the multiple adsorption–desorption cycles. The desorption kinetics were similar to those observed in the ad-sorption process. The desorption process was not significantly affected by temperature.

Development of Artificial Neural Network Models for Biogas Production from Co-Digestion of Leachate and Pineapple Peel

The processes of anaerobic digestion and co-digestion are complicated and the development of computational models that are capable of simulation and prediction of anaerobic digester performances can assist in the operation of the anaerobic digestion processes and the optimization for methane production. The artificial neural network approach is considered to be an appropriate and uncomplicated modelling approach for anaerobic digestion applications. This study developed neural network models to predict the outcomes of anaerobic co-digestion of leachate with pineapple peel using experimental data. The multilayered feed forward neural network model proposed was capable of predicting the outcomes of biogas production from the anaerobic co-digestion processes with a mean squared error for validation of 2.67 x 10-2 and a R value for validation of 0.9942. The approach was found to be effective, flexible and versatile in coping with the non-linear relationships using available information.

Effects of Microwave Irradiation on Activation Energy and Reaction Rate of Synthesis of Dodecylmethyldihydroxyl Ammonium Bromide

The reaction kinetics of the synthesis of quaternary ammonium salt under two sets of different reaction conditions, including microwave irradiation condition and conventional heating condition, were studied. In order to make sure that the microwave would not be interrupted, the reaction temperature was maintained at the boiling point of reaction solvents. The results showed that the reaction was a first-order reaction under both set of conditions and microwave irradiation changed the value of the activation energy of the reaction, indicating a change in the reaction mechanism. The activation energy was 41.44 kJ/mol under microwave irradiation condition, and 61.21 kJ/mol under conventional condition.

New Allometric Scaling Relationships and Applications for Dose and Toxicity Extrapolation

Allometric scaling between metabolic rate, size, body temperature, and other biological traits has found broad applications in ecology, physiology, and particularly in toxicology and pharmacology. Basal metabolic rate (BMR) was observed to scale with body size and temperature. However, the mass scaling exponent was increasingly debated whether it should be 2/3, 3/4, or neither, and scaling with body temperature also attracted recent attention. Based on thermodynamic principles, this work reports 2 new scaling relationships between BMR, size, temperature, and biological time. Good correlations were found with the new scaling relationships, and no universal scaling exponent can be obtained. The new scaling relationships were successfully validated with external toxicological and pharmacological studies. Results also demonstrated that individual extrapolation models can be built to obtain scaling exponent specific to the interested group, which can be practically applied for dose and toxicity extrapolations.