Environmental Health Risk Assessment of Fe, Zn, As, Cd and Pb Concentration in Selected Asian Rice Grain (Oryza sativa)

This study was carried out to determine the concentration of chemical elements in food grains (Oryza Sativa). A total of eight brands of rice grains was selected which are commonly sold in major hypermarkets in Malaysia. The selection was based on the countries of origin (COO) namely Cambodia, Indonesia, Malaysia, Thailand, Vietnam, China, Japan and Taiwan. A total of 16 rice grain samples included both polished and unpolished rice grains in order to determine the concentration of Fe, Zn, As, Cd and Pb. From the laboratory result, it was found that the concentration of Fe, Zn, As, Cd and Pb was ranged from 0.067-14.446 mgkg -1 , 0.308-12.335 mgkg -1 , 0.000-0.048 mgkg -1 , 0.000-0.604 mgkg -1 and 0.000-0.418 mgkg -1 respectively. The rice grains samples from Vietnam, China and Cambodia showed that carcinogenic cancer risk for both adults and infants’ group (Cumulative lifetime cancer risk, CLCR >1x10 -4 ).


Environmental Management and Sustainable Development
Asia and it has a very high potential to be affected by contamination through air, water and soil (Hoornweg et al., 2013). Heavy metals are the most common pollutants as they can be found in water, land and air pollution and therefore they have higher probability to influence the paddy rice (Viet and Yabe, 2013). Heavy metals contamination by Cd, Pb, Zn and Cr are serious environmental problem which are caused by numerous anthropogenic activities (Tan et al. 2018). These chemical elements capable to pose a danger to human health since they are non-biodegradable, can be accumulated and can enter the human body through the food chain (NCBI 2015;Kong et al., 2018).
Heavy metals are categorized into carcinogenic and non-carcinogenic (Liu at al., 2016) The International Agency for Research on Cancer grouped arsenic and lead as both carcinogenic and non-carcinogenic elements whereas cobalt, copper, iron, aluminium and zinc as non-carcinogenic (NCBI, 2014). Heavy metals which are classified as carcinogenic elements are those that have the potential to induce tumours when they get into the body through various pathways such as ingestion. Other non-carcinogenic heavy metals can cause other health problems even though they do not cause cancer if they present in large quantities. For example, highly concentrated copper may lead to chronic toxicity in body which cause heart problems, jaundice, coma and even death (NCR, 2000).
Paddy crops are cultivated in water flooded conditions which enhance the ease of pollutants uptake (GRiSP, 2013). As a result, heavy metals are more easily to be absorbed and stored in rice grain as compares with other food. Humans and animals have a higher chance to be influenced as rice acts as producer in the food chain.

Collection and Preparation of Rice Grain Samples
Total eight brands of rice grain were selected which are being sold in major hypermarkets in Malaysia. The selection was based on the countries of origin (COO) namely Cambodia, Indonesia, Malaysia, Thailand, Vietnam, China, Japan and Taiwan. A total of sixteen samples for both polished and unpolished rice grain from each country were collected in order to carry out the laboratory test to identify heavy metals concentration which was used to conduct human health risk assessment. The samples preparation and processing were conducted according to Praveen and Omar (2017).

Trace Elements Determination
The elements namely iron (Fe), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb) were selected in this study. The analysis method was adopted according to Ma et al. (2017). The stock solution that contained As, Pb, Cd, Zn and Fe was used to prepare solutions with different concentrations (1, 10, 20, 50, 100ugL -1 ) by using ultrapure water and volumetric flasks and ready to be used in inductively coupled plasma mass spectrometry (ICP-MS) Perkin elmer nexion 2000. Three replications for each sample was tested by ICP-MS

Human Health Risk Assessment (HHRA) Procedure
Due to absence of cancer slope factor (CFS) by consumption data for Cd, only As and Pb Environmental Management and Sustainable Development ISSN 2164-7682 2020 were selected in the determination of carcinogenic health in this study. According to USEPA, Equation 1 was used to find the Average Daily Dose (ADD); Equation 2 was used to find the Hazard Quotient (HQ); Equation 3 was used to find the hazard index (HI); Equation 4 was used to find the Lifetime Cancer Risk (LCR); Equation 5 was used to find cumulative lifetime cancer risk (LCRT) (USEPA 2016). The summary of the constant value for the huma health risk assessment determination were shown in Table 1-3. ADD(mg/kg.day) = ( C × IR × ED × EF ) / ( BW × AT ) (1)

Results and Discussion
The average for selected elements concentration found in polished and unpolished rice grain collected from eight countries (Vietnam, China, Cambodia, Indonesia, Malaysia, Thailand, Taiwan, Japan) are shown in Table 4 -5 respectively. Some of the elements in samples were not detected by the ICP-MS therefore were indicated as "n.d.". The highest concentration of Fe, Zn, As, Cd and Pb in both polished rice grain determined in this study were 14.45mgkg -1 , 12.34mgkg -1 , 0.048mgkg -1 , 0.156mgkg -1 and 0.418mgkg -1 respectively.
According to NCBI (2014), the higher concentrations of heavy metals may pose higher human health risk since many adverse human health issues are associated with concentration of heavy metals adopted in human body. The increase of heavy metals concentration in the environment because of human activities such as mining and natural deformation such as weathering of the earth's crust has increased the human health risk since the heavy metals cannot be biodegradable and can enter human body through inhalation, dermal contact and ingestion. Therefore, it is essential to determine the concentration of heavy metals in rice grain and estimate its risk to human health. The toxicity of heavy metals is associated with the absorbed dose, exposure path and exposure duration. Hence, rice grain which act as a staple food in Asia should be demonstrated with low and acceptable heavy metals concentration. ISSN 2164-7682 2020   countries were not detected except the polished rice grain sample from China exceeded the permissible concentration (0.2mgkg -1 ) set by FAO/WHO (1984). However, it is under the permissible limit (2.0mgkg -1 ) set by Malaysia Food Regulation (1985).

Environmental Management and Sustainable Development
According to Hironori (2012), small paddy farms are practiced in China, Indonesian Java, and Red River Delta in Vietnam which have average size less than 0.5 ha; the size of paddy farms in Bangladesh, Eastern of India, and the Mekong River Delta in Vietnam have average size of less than 1 ha.; the paddy farms in Japan have average size of about 1 ha.; the rice farms in most other Asian countries have average size of 1-2 ha.; the rice farms in Thailand, Myanmar, Cambodia, and Punjab, India are average farm size larger than 2 ha. (Yagi, 2012;Ji et al. 2016). Hence, it cannot be concluded that the amount of heavy metals assimilated by the rice grain is constant concentration. The concentration of heavy metals in soil may not be the same as uptake concentration. There may be factors that influence the growth of rice grains that affect the heavy metal assimilation. Those paddy crops that are cultivated under the optimal conditions where sunlight exposure, water provision and nutrients provision are optimum, may contain more heavy metals. In a large paddy field, it is impossible to ensure that the sunlight, water and nutrients are distributed evenly to every area since the composition of soil may slightly be different and many other unknown factors may disturb the distribution such as invertebrates which are living in soil which may change the characteristic of soil.

Human Health Risk Assessment
Human health risk assessment was conducted based on the result obtained from laboratory analysis. The calculated hazard quotient and hazard index are tabulated in Table 6 and 7. For adult receptor group, the hazard quotient and hazard index for all polished rice grain samples are determined as lower than the risk level limit (1.0) except China's sample (HQ cd = 1.579, HQ Pb = 1.058, HI = 3.182). On the other hand, the hazard quotient and hazard index for all unpolished rice grain samples were below the risk limit except Indonesia samples (HQ cd = 6.115, HI =6.237).
In the children receptor group, the hazard index of China polished rice samples was determined as exceeded the risk level limit (HQ cd = 5.074, HQ Pb = 3.399, HI= 10.222). Also, the unpolished rice grain sample from Indonesia was found to have unacceptable hazard index >1.0 (HQ cd = 19.647, HI = 20.037). The calculated hazard quotient is based on the reference dose which is safe to human health. The concentrations of Cd, Zn and Pb in some rice grain samples exceeded the permissible level for safe consumption and also can pose severe health risk to human. High cadmium concentration can cause human health problems. For examples, it can pose significant damage to kidney and has the potential to induce tumor effects and thus its risk to human health is high. An incident in Japan, many victims in Japan who were living near to the contaminated area had developed Itai-itai disease because of cumulative cadmium exposure through ingestion (Nishijo et al. 2017).
Hence, the amount of daily intake should be reduced so that it will not develop significant effects to human health (USEPA, 2011). Although the hazard values of the selected trace elements may not be in excess of 1.0. it doesn't mean that the rice is safe for consumption Environmental Management and Sustainable Development ISSN 2164-7682 2020 daily because full health risk description is not enough (Praveen and Omar 2017) Therefore, the hazard index which is the cumulative hazard values from selected trace elements are calculated since cumulative exposure can increase the risk. Thus, the hazard index which is more than 1 will also pose potential health risk although the individual hazard value is less than 1. The hazard index (HI) and hazard quotient (HQ) are used to describe the non-carcinogenic health risk, whereas the carcinogenic health risk is described by the lifetime cancer risk. The acceptable range of lifetime cancer risk according to the standard in Malaysia is ranging from 1x10 -6 to 1x10 -4 . For carcinogenic elements Arsenic (As) and Lead (Pb), the life time cancer risk values were determined based on Equation 4 and 5. As shown in Table 8, the polished rice samples from Vietnam, China and Cambodia showed LCR As for both children and adult exceeding LCR limit, especially for China's polished rice grain LCR As, children . This study found that the polished rice sample from China exceeded acceptable level (2.34 × 10 -3 ).
From the study, results for cumulative lifetime cancer risk (LCR As, Pb ) for both adults and children receptors were 7.65x10 -4 and 2.46x10 -3 respectively, both had exceeded the Malaysia's LCR standard. The cumulative lifetime cancer risk is increased due to the presence of individual lifetime cancer risk of Arsenic (As) in rice grain sample from China. The increase in cumulative lifetime cancer risk shows that daily consumption of rice have higher risk to get cancer. Overall, the polished rice grains and its products imported from Vietnam, China and Cambodia didn't pose potential carcinogenic health risk to adult and children in Malaysia. ISSN 2164-7682 2020 Table 8. Lifetime cancer risk for adult (LCR As, adult ; LCR Pb, adult ) for different polished rice samples from different countries in rice and more efforts from industries which produce waste that contains heavy metals, agricultural sectors and government are needed to counter the problems.