Pesticide Residues in Rice

History of rice

Rice is one of the oldest agricultural products known to humanity. Since the dawn of civilization, it has been used as a vital grain in the humid regions of Asia and, to some extent, in West Africa. Evidence of early rice cultivation exists in many civilizations, including China, India, and Southeast Asia. The oldest archaeological evidence of rice cultivation dates back 8,000 to 9,000 years to China, while in India, evidence of cultivation dates back to around 3,000 to 3,500 years ago. Rice was first introduced to Europe by Muslims in the eighth century through Spain and Portugal, and rice cultivation later spread to Italy. Additionally, rice was introduced to America for the first time in the 17th century (1685) via ships from Madagascar, which eventually led to rice cultivation in the region. Although the exact date of rice's introduction to Iran is unclear, some evidence suggests it arrived during the Achaemenid period via trade routes from India. However, it became widely cultivated during the Sassanid period, particularly in northern Iran, especially in Gilan and Mazandaran. In this way, rice spread from Asia to Europe and the Americas, eventually becoming widespread worldwide.

Importance of rice in the world and Iran

Rice is one of the most consumed cereals and an excellent source of carbohydrates and energy. In the period from 2022 to 2023, approximately 520 million tons of rice were consumed worldwide. Among Asian countries, China, India, Indonesia, Bangladesh, and Vietnam are the largest consumers of rice. For example, rice consumption in China and India in 2023-2024 is 150 million tons and 118 million tons, respectively. In Iran, rice is the second most consumed crop after wheat. Given the tastes of the Iranian people, rice is considered one of the essential daily needs of the country and an essential item in household consumption baskets. Annually, about 3.6 million tons of rice are consumed in Iran, meaning each Iranian consumes about 40 kilograms of rice annually.

Major rice-producing regions in Iran

Due to the high water requirements of rice, the majority of rice-growing lands are located in the northern provinces of Iran. Over 70% of rice cultivation takes place in three northern provinces (Gilan, Mazandaran, and Golestan). Due to the vast area under rice cultivation in these regions and the presence of harmful pests such as the rice stem borer, rice leaf roller, paddy fly, and major diseases like rice blast, pesticide use is most common in these areas.

Use of pesticides in rice

Today, farmers use large quantities of agricultural chemicals, such as pesticides, to maximize crop yields by controlling pests. Around 100 species of insect pests are known to attack rice crops worldwide, with 30 of them causing significant damage. Pest damage to rice is due to the warm and humid conditions in the fields, as well as unfavorable storage conditions that lead to the presence of insects, mites, fungi, molds, and rodents in storage.

Pesticide residues in rice

Pesticide residues in agricultural products refer to chemical substances that may remain on crops after the use of pesticides to control pests, diseases, etc. These residues may include pesticides, chemicals, or their by-products that are transferred directly or indirectly to agricultural products and pose a potential threat to public health. The maximum allowed level of pesticide residues, or Maximum Residue Levels (MRLs), refers to the highest concentration of a chemical residue in a product. These levels are expressed in milligrams per kilogram or ppm (parts per million). MRLs are set by relevant organizations and authorities to ensure that products are within the safe residue limits and to guarantee consumer safety. Lack of knowledge or awareness by farmers regarding pesticide use, the poor quality of pesticides, the use of non-permitted pesticides, multiple sprayings, and not adhering to the pre-harvest interval (the minimum time between the last pesticide application and harvest) are among the key reasons for the presence of pesticide residues above the allowed limits. If pesticide residues exceed the allowed limits, they may pose a health risk to consumers and can also lead to the rejection of export shipments in global markets, causing economic loss.

Pesticide residues in rice according to Iranian National Standards

The maximum permissible levels of pesticide residues in rice must comply with Iranian national standard number 13120 (Pesticides-Maximum Residue Levels-Cereals).

http://standard.inso.gov.ir/StandardView.aspx?Id=57415

Maximum residue levels of pesticides in rice according to EU Standards

The allowable residue levels of pesticides in rice according to European standards can be accessed through the following link:

https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A02005R0396-20240226

Health risks to humans from pesticide residues

One of the main routes through which pesticides enter the human body is by consuming food contaminated with pesticide residues. Over time, this can have detrimental effects on human health. Conditions such as hyperactivity, autism (serious problems with social interactions, verbal and non-verbal communication, and repetitive behaviors), respiratory issues, particularly asthma, chronic obstructive pulmonary disease (COPD), heart disease, kidney disorders, chronic autoimmune diseases (like joint pain), skin rashes, fatigue, rheumatoid arthritis, genetic damage, insomnia, and cognitive disorders (difficulty remembering and processing information) have been associated with pesticide exposure.

Among the widely used pesticides in the world on various products, including rice, organophosphates are common. Long-term exposure to these chemicals can lead to neurological effects such as moderate Down syndrome (intellectual disability), behavioral disorders (which can be dangerous over time), cognitive deficits, negative impacts on pervasive developmental disorders (delays in developing social skills, language, communication, etc.), depression, anxiety, suicidal thoughts, liver dysfunction, endocrine disruption, reproductive issues, infertility, miscarriage, diabetes, Alzheimer's disease, Parkinson's disease, and breast cancer (the most common cancer linked to organophosphates).

Other pesticides, such as organochlorines, are more persistent than organophosphates. These pesticides accumulate in fat tissue and can cause long-term adverse effects such as carcinogenicity, reproductive disorders, neurological problems (e.g., Parkinson's), endocrine disruptions, premature births, delayed fetal development, increased infant mortality, low birth weight, multiple sclerosis (MS), eczema, early puberty, prostate cancer, blood pressure issues, type 2 diabetes, and gestational diabetes.

Sensitive groups to pesticide residues

Children: Fetuses, infants, and young children are particularly vulnerable to the long-term effects of pesticides because their organs are not fully developed, and they are continuously going through critical growth phases. During these phases, a child's developing brain is learning and growing, and if it fails to develop certain skills, such as language or motor skills, it can lead to permanent damage. Furthermore, children consume more food and beverages relative to their body weight compared to adults. Additionally, infants and young children, due to immature livers and detoxification systems, cannot effectively eliminate pesticide residues from their bodies, potentially affecting their overall health and nutrient absorption. Chronic exposure to even low levels of pesticides is more dangerous to children than acute exposure. Long-term exposure to low levels can lead to behavioral and cognitive problems, cardiovascular diseases, respiratory issues such as asthma, leukemia, brain cancer, neuroblastoma (malignant tumors of the kidney), and bone tumors in children. Cancer is the second leading cause of death in children, with leukemia being the most common. Brain tumors and lymphomas are ranked second and third, respectively.

Pregnant Women: Pesticide residues entering the body of a pregnant woman can pass through the placenta and the blood-brain barrier of the fetus, potentially increasing the risk of birth defects at birth or several years after childhood. Common birth anomalies related to pesticide exposure include preterm birth and low birth weight. Numerous studies have also shown a positive association between pesticide exposure and spontaneous miscarriage or fetal death.

The table below provides a comprehensive overview of some commonly used pesticides on rice, including their group, pesticide type, cancer risk based on the International Agency for Research on Cancer (IARC) classification, mode of action, and whether or not the pesticide can be removed or degraded.

1-Non-systemic Pesticides: These contact pesticides affect target pests upon contact. They do not necessarily penetrate plant tissues and, as a result, are not transported through the plant's vascular system.

2-Systemic Pesticides: These pesticides effectively penetrate the tissues of the plant (leaves, stems, or roots) and move through the plant’s vascular system to eliminate specific pests.

3-Relatively Systemic Pesticides: These pesticides have the ability to be absorbed and distributed within the plant, but this capability is not as pronounced as that of fully systemic pesticides. They typically concentrate in specific parts of the plant, such as leaves or roots, and are transferred to other parts of the plant to a lesser extent.

Pesticide residues in second-crop rice

Research conducted on the water and soil of paddy fields in the northern provinces of Iran, especially in Mazandaran, for both the first and second rice crops, revealed that the use of organophosphate pesticides, such as diazinon, to control rice stem borers is widespread in this province. After harvesting the first crop (in August), farmers quickly begin preparing the land and transplanting rice again. The farmers believe that since the time between the last pesticide application and the harvest of the second crop (mid-autumn) is longer compared to the first crop, the second crop will be healthier. However, because the second crop coincides with the third generation of rice stem borers, which appear from late July to early August, the use of chemical pesticides increases. Based on research and sampling of pesticide concentrations in the water and soil of the region, the results indicate alarmingly high levels of diazinon pesticide in the second crop. It can be said that second-crop rice is more contaminated with pesticide residues than first-crop rice.

Comparison of brown and white rice in terms of pesticide residues

Brown rice, due to the preservation of the bran layer, may contain more pesticide residues. The potential health risks and benefits associated with consuming brown rice more than white rice are not well understood. Studies of pesticide residues on both white and brown rice have shown that fat-soluble pesticides are often found in brown rice, which contains more protein and fat compared to white rice. The fats in brown rice are mainly located in the bran. During the processing of brown rice, particularly in the milling and removal of the bran, a significant amount of these pesticides (including fat-soluble ones) are removed. The fat content in brown rice is about 3%, while in white rice it is approximately 0.8%. The concentration of pesticide contaminants in brown rice is higher than in white rice.

Indian rice and pesticide residues

Annually, approximately 3.6 million tons of rice are consumed in Iran, with more than 2 million tons produced domestically, and 1.2 to 1.5 million tons imported. The largest import source for rice in Iran is India. The extensive use of agricultural chemicals and pesticides that are now banned by international standards has led to warnings from the European Union about rejecting rice shipments from India to important markets such as the United States, the European Union, Australia, and Japan. Indian rice, due to its lower price compared to Iranian rice, has gained significant popularity in Iran. Rice currently available in the market, with a health certificate for import, has been tested and is considered safe and compliant with Ministry of Health standards. However, if rice imports to Iran are made outside commercial regulations, without proper testing, and illegally by profiteers, it can pose a serious health threat to the public.

Home methods to reduce pesticide residue intake from rice

The pesticide contamination in rice can be reduced through the following home methods:

Step 1: Initially, place the rice in a suitable container. Then, under running water, gently stir the rice 5 to 6 times and rinse it until the washing water runs clear.

Step 2: Soak the washed rice in a container with a specified amount of water (1 cup of rice and 6 cups of water) overnight before cooking.

Step 3: Discard the soaking water from the rice.

Step 4: Cook 1 cup of rice with 6 cups of water. When the water in the cooking pot reaches boiling point, add the rice and let it cook for 10 minutes.

Step 5: After cooking, drain the rice to discard the excess water.

To reduce the risks of pesticide residues for consumers, the method of boiling and draining the rice is better than cooking it in the pot.