X-Ray Fluorescence (XRF) Analyzer - Theory, Utility, and QA/QC for Environmental and Commercial Product Samples in Cambodia

Laboratory facilities in developed countries provide a variety of options for analysis of environmental samples and commercial commodities that could impact human health. The same is not true in developing countries and there is a great need to identify technologies that could be used to provide robust, accurate, cost-effective analysis that minimizes the need for extensive technical training. An X-ray Fluorescence (XRF) analyzer seems to be an analytical technique that could be such a tool for developing countries. Therefore, the objective of this thesis was to assess the performance and utility of a handheld, portable XRF unit in analyzing different types of environmental and commercial commodity samples in Cambodia. Because a number of different materials were analyzed, this thesis has a slightly different format than typical. Each of the following three chapters has its own methodology, results and discussion sections. This approach was taken because the materials analyzed and methods for sampling the materials were so different, it was clearer to separate the analyses into separate, individual chapters. This abstract provides a brief overview of each chapter. 1. Chapter One The need to have a more robust, cost effective and less time-consuming form for environmental samples in the field where samples could not be brought in for the laboratory analysis led to the manufacture of a first X-ray fluorescence (XRF) analyzer. This first chapter outlines the theory of the XRF, its advantages and limitations, and provides some QA/QC of a handheld XRF (XL3t 900, Billerica, MA) on skin whiteners, which were purchased and donated by university students for mercury levels. The results showed that up to 98 samples (16%) of creams analyzed contained mercury higher than 20 ppm, and 64 concoctions out of 192 samples were contaminated with more than 20 ppm mercury. Although there were suppressions (20%) of mercury at concentrations near 15,000 ppm (i.e. an under-estimation), the XRF proved to be an excellent tool capable of detecting metals; particularly mercury in semi-solid solutions. 2. Chapter Two Phnom Penh, the capital city of Cambodia, is home to some 1.4 million people and undergoing urbanization. In spite of its urbanization, Phnom Penh has yet to have a primary wastewater treatment plant and adequate sewage drainage system in place. There are two main interceptor sewer channels that drain wastewater and storm water from the southern part of the city into a natural wetland, Boeung Cheung Ek. These two sewer channels are the Tum Pun Sewer System and the Meanchey Sewer System. These are open sewer systems which collect all types of industrial, hospital, institutional and household wastes, and in turn discharge into the wetland. In Cambodia data related to metals contamination in sediment and street dust are very limited. So, this chapter of the thesis seeks to determine metal concentrations, spatial patterns and sources in sewer, wetland and street dust samples. Metals levels also are compared with United States Environmental Protection Agency (USEPA), New York State Department of Environmental Conservation (NYSDEC), and Provincial Sediment Quality (PSQ), Ontario, Canada guidelines. The results showed that although there are elevated metal concentrations in the sewer and wetland sediments and street dust samples, they are still lower than those reported elsewhere such as in Hong Kong, Greece, China, Korea, the US, and Malaysia. One sewer site (M1) had significantly higher metals levels than any other site of the two sewer systems, because it is geographically surrounded by industries and factories. The metal concentrations, especially Pb, Zn, and Cu, decreased with distance from this site. The levels of Pb in street dust appeared higher in high-density traffic areas and decreased with distance from the busy traffic streets. Although leaded gasoline can be a source of lead in street dust and sediments, Cambodia apparently complies with the EU guideline on the level of lead use in gasoline. In addition to leaded gasoline, diesel fuel can also contain metals but the levels are subject to further analysis. Other sources of metals in street dust include tire abrasion, brake lining and transmission oil. To reduce the levels of metals, the two sewer systems should be dredged periodically. The dredging also would increase channel flow capacity during storm events. Source tracking of metals should be conducted in more detail to inform management strategies. For the management of street dust, street sweeping and washing may be effective means to allay the metal toxicity levels. 3. Chapter Three Lead (Pb), which is a potentially hazardous toxicant, can be an additive agent of jewelry items and children’s toys. It is added to polyvinylchloride (PVC) pipes, so that it would provide rigidity, lower manufacturing costs and resistance to sunlight. Lead also has been a paint additive and this is of great concern in North America. Cambodia imports most of its consumer goods from other countries, but the regulatory inspection on imported products is not strictly enforced due to the lack of customs inspection tools, facilities and trained professionals. The purpose of this chapter is to assess jewelry items, children’s toys and paints for potential metal contamination from various markets in Phnom Penh, Cambodia and Bangkok, Thailand by means of the handheld X-ray fluorescence (XRF) analyzer. The results indicated that significant levels of Pb were used in the products (up to 43% in jewelry items and 4.3% in paints). These findings suggested that more restrictive regulations on the sales and use of toxic products should be imposed, so that health risks can be minimized. The XRF was manufactured, and over the years, has been re-engineered to provide the features necessary to operate in the field where laboratory-based assays not are suited. The XRF has some limitations for some elements like Cr and Hg in soils, the analyses of which necessitate laboratory-based verification such as an AAS or ICP. It also does not have the capacity to assess the degree of dermal and oral absorption of metals, although these aspects are still evolving. Nonetheless, the XRF would be an ideal tool for on-site and in situ investigation in Cambodia; particularly for customs officers, environmental researchers and engineers

Leaded Paint in Cambodia—Pilot-scale Assessment

Background. Lead is a heavy metal that is well known to pose a threat to human health. Although the sale and use of lead paint has been banned in much of the developed world, lead is still commonly used in enamel paints in the developing world, including Cambodia. As Cambodia's economy grows, this may increase the purchase and use of lead-based paints, thus potentially exposing more of the population to the toxic effects of lead. Objective. This study was performed to evaluate the concentration of lead in enamel paints in Cambodia using a method that is quick, effective, and cost-efficient. Methods. A handheld X-ray fluorescence analyzer was used to evaluate 21 samples of enamel paint, including 8 replicates that were randomly purchased from three shops in Phnom Penh, Cambodia to evaluate the level of metals. All of the paint samples in the current study were manufactured in Thailand. Discussion. Ninety percent of the enamel paints sampled in Cambodia exceeded the voluntary standard of 100 μg/g lead of the producing country, Thailand. The mean and median levels for lead were 11,833 μg/g, and 4,961 μg/g, respectively. Conclusion. Based on our pilot-scale assessment, high levels of lead appear to be common in enamel paints in Cambodia, and a fuller assessment of the situation is warranted. Import and production of such toxic products should be avoided and appropriate labeling and public warnings should be provided

Metal Contamination in Low-Cost Jewelry and Toys in Cambodia

Background. The existence of lead-contaminated consumer products is a global issue. Toys and low-cost jewelry may contain toxic metals and Cambodia is known to have consumer products with toxic metals. Objectives. It is important to inform Cambodians about sources of toxic metals so that they can reduce their exposure risk, particularly for children. Methods. Student volunteers purchased, or brought from home, low-cost jewelry and toys to either the University of Health Science or a Don Bosco Institute in Phnom Penh, Cambodia, where they were analyzed using X-ray fluorescence (XRF). The initial analysis was performed in 2011. A subset of the 2011 samples was re-analyzed in 2015 using new preparation techniques and a new x-ray fluorescence (XRF) unit. Discussion. The analysis of low-cost jewelry in Phnom Penh in 2015 indicated that lead in jewelry clasps is a more serious health concern than was first perceived in 2011. Mercury, nickel, cadmium and copper were also found in toys, and occasionally these toys had been produced by well-known companies. Sources of jewelry production of samples in the present study are unknown. Lead in clasps in low-cost jewelry appeared to be the greatest risk to children in our sampling. Conclusion. One-third of toys and low-cost jewelry exceeded the United States and European Union guidelines for heavy metals. XRF analysis allows for rapid screening of lead and other toxic metals and could be used to reduce the sales of low-cost jewelry and toys containing toxic metals. Competing Interests. The authors declare no competing financial interests

Mercury Contamination of Skin-whitening Creams in Phnom Penh, Cambodia

Background. In Cambodia, there is widespread use of skin-whitening creams containing levels of mercury that exceed Association of Southeast Asian Nations (ASEAN) guidelines by up to 35,000 times. Mercury in skin-whitening creams threatens to compromise the health of Cambodians. Objectives. It is important to provide essential information on sources of mercury so that Cambodians can avoid exposure to elevated levels of mercury and to support informed management of consumer goods. Methods. Students were directed to buy selected skin-whitening creams that were then sampled with replication in 2011 and 2015 and processed with X-ray fluorescence (XRF) at the University of Health Science (UHS), Phnom Penh, Cambodia. Discussion. The analysis of skin-whitening creams in Phnom Penh in 2015 was compared to analyses in 2008 and 2011 and showed that several creams produced in Asia no longer contain mercury. However, skin creams produced in Phnom Penh continue to use mercury and counterfeit products also are contaminated with mercury. Vendors occasionally identified Vietnam as a source of counterfeit products, but often the source was unknown. Mercury continues to be the metal of greatest concern in skin creams. Creams with more than 1,000 μg/g of mercury are a common cause of dermatitis (27% of cases). A new XRF analyzer was also able to detect more lead and arsenic than that used in analyses performed in 2011, and these two metals also exceeded ASEAN guidelines. Arsenic contamination also reflected the presence of bismuth in creams. Conclusion. Some producers of skin-whitening creams in Thailand, China and Taiwan appear to be aware of the risks of mercury contamination and have modified their products. However, other producers of skin-whitening creams continue to use mercury. XRF analysis allows for rapid screening of mercury in cosmetics and should be used to gather additional information on mercury content in cosmetics in support of public health efforts to stem the import, export and sales of skin creams containing mercury

Application of Handheld X-Ray Fluorescence Analyzers to Identify Mercury in Skin-Whitening Creams in Cambodia

Background. A well-documented source of mercury contamination is skin-whitening cream. The heavy metal is sometimes added to the cream to block production of melanin. Past studies have shown that about one third of skin whitening creams for sale in Phnom Penh contained mercury levels considerably higher than both United States and Association of Southeast Asian Nations (ASEAN) guidelines. Developing nations such as Cambodia do not have the resources for monitoring and enforcement. Objectives. Evaluate the utility of handheld X-ray fluorescence analyzers for detection of mercury in skin-whiteners. Methods. A handheld XRF unit was used to measure the total mercury content of 676 skin-whitening creams collected from volunteers from a cross-section of Phnom Penh’s residents. Results. About 16% of bleaching creams collected contained more than 20 ug/g of mercury. The highest concentration was about 35,000 ug/g. A third of the samples that were custom-made or modified by beauty shops contained more than 20 ug/g of mercury. Conclusions. The handheld XRF analyzer proved an excellent tool for screening mercury in skin creams, and could be particularly useful in developing countries because it is relatively inexpensive, requires no sample preparation or extraction, can be used by staff with little technical background, and can facilitate on-site education. Competing Interests. The authors declare no competing financial interests