Plasticizers (carcinogen)
Plasticizers are chemical additives used to enhance the flexibility, strength, and durability of various polymers, including polyvinyl chloride (PVC), which is commonly found in items such as food packaging, medical devices, and children's toys. The most widely used plasticizers belong to the phthalate family, such as di(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DOP). While these substances play a crucial role in manufacturing, they are known to leach into the environment and food, especially when exposed to heat or greasy substances, leading to widespread contamination.
Concerns have been raised about the potential carcinogenic effects of plasticizers, particularly phthalates, which have shown to cause tumors in rodent studies. However, translating these findings to human health is complex and not fully understood, with limited epidemiological data available. The potential for plasticizers to disrupt endocrine function, especially in children and developing fetuses, has heightened worries about their health implications.
Regulatory bodies, such as the European Union, are taking steps to restrict certain phthalates, while research is ongoing to develop safer, biodegradable alternatives for use in consumer products. Overall, the debate around plasticizers encompasses health risks, environmental impact, and the need for further study into their effects on human health, particularly for vulnerable populations.
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Plasticizers (carcinogen)
DEFINITION: Plasticizers are chemical substances that impart flexibility, strength, and durability by being used as additives during the manufacture of various polymers, such as polyvinyl chloride (PVC), food packaging, food storage containers, children’s toys, and medical devices.
Types of plasticizers: A large variety of chemicals are used as plasticizers. They are classified into various categories based on their chemical structure. The most widely used plasticizers are derived from the family of dicarboxylic esters and are commonly known as phthalates: Examples include di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DOP), adipates, and maleates. Chemicals from the family of organophosphates and some glycol esters are also used as plasticizers.
Uses: Phthalates such as DEHP are predominantly used in manufacturing PVC, one of the oldest polymers used to make pipes and various plastic containers. Phthalates are also used as plasticizers in medical devices such as dialysis bags, intravenous bags, and tubing. They are also used in detergents, lubricating oils, flooring materials, food packaging materials, and storage containers.
Environmental exposure: Plasticizers are not covalently bound to the plastic matrix, and they consequently leach out when in contact with oils, fats, and other greasy substances, especially at higher temperatures. This is especially true of phthalates, used in food wraps and containers. Plasticizers in food wraps have been shown to migrate into and contaminate fatty foods such as meat, cheese, and oily snacks. Plasticizers are also released into the environment directly while manufacturing plastics and from discarded plastic containers, wraps, and pipes. As plastics have myriad uses, the plasticizers in them are ubiquitous contaminants of air, water, food, and medicines. Human exposure to plasticizers is mainly through ingesting water and food contaminated with them. Infants are exposed to plasticizers when they chew or suck on plastic toys or pacifiers or drink liquids out of plastic feeding bottles. Another source of exposure is through air, in which plasticizers such as DEHP adhere to aerosol particles. Animal studies have shown that phthalates can cross the placental barrier, and therefore, this can potentially cause prenatal exposure in humans.
Toxicity and metabolism: Toxicity studies on plasticizers (especially the phthalates DEHP and DOP) have been done on rodents through various exposure routes. It has been found that rodents metabolize phthalates readily, and the liver and kidneys are common target organs for general toxicity. The primary concern about the toxicity of phthalates stems from reports from the US National Toxicology Program showing several of them to be carcinogenic in rodents. The mechanism of carcinogenesis in rodents or other species is as yet unclear, and there are no clear-cut studies extrapolating the animal data to humans. Many industry groups and advocacy panels have analyzed the animal data on the toxicity of plasticizers and have failed to come to a consensus because the toxicity patterns vary significantly by species and routes of exposure. Still, studies on rats appeared to confirm DEHP caused an increase in testicular and pancreatic tumors in rats, and, in a separate study, liver tumors in mice and rats. Plasticizers have been detected in breast milk and children’s blood samples, but there are no studies that clearly relate childhood exposure to the risk of adult human cancers. Therefore, childhood exposure to plasticizers is shrouded in controversy. Human epidemiological data remains limited, and, therefore, definitive conclusions on humans and the carcinogenic effects of plasticizers remain limited.
Some reports in literature indicate that plasticizers, especially phthalates, act as hormone disrupters. Hormones are chemical messengers produced by various glands, called endocrine glands, in animals and humans that travel through the bloodstream and regulate growth, reproduction, and metabolic functions in the body. This system, known as the endocrine system, is a very finely tuned mechanism in the body, and endocrine disrupters can readily throw it off balance, creating significant health and cancer risks. Young animals and children are more vulnerable to exposure to such disrupters because their systems are still in the developmental stage, so there is a great concern regarding the exposure of infants and children to phthalates.
Preventive measures: Because plasticizers are widely distributed environmental contaminants, there is a great deal of concern regarding cancer and other health risks to adult human populations due to the exposure of infants and children to environmental endocrine disrupters. The conflicting conclusions from various animal studies and the lack of data extrapolating the animal exposure studies to human infants and adults underscore the complexity of the science. More studies delineating the toxicokinetics of plasticizers, especially in vulnerable subpopulations, such as pregnant and lactating women, premature infants, and children, are needed. There are many ongoing studies to assess the risk of exposure to plasticizers and evaluate the potential of early childhood exposure in increasing the risk of cancer in adults.
The European Union has recommended banning the use of certain phthalates. In the US, DEHP is listed as a reasonably anticipated to be a human carcinogen in the Fifteenth Report on Carcinogens released by the National Toxicology Program. Toy manufacturers are funding research to develop newer plasticizers with greater biodegradability and lower toxicity, such as alkyl citrates and esters of vegetable oils. These environmentally benign plasticizers are being developed for use in food-packaging materials, medical devices, and children’s toys.
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