Potential Risks of The Antimicrobial Agents on Human and Animal Health

Triclocarban (3,4,4’-trichlorocarbanilide; TCC) and triclosan (5-chloro-2-(2,4-dichlorophenoxy) phenol; TCS) are antimicrobial agents widely used in various personal care products such as liquid and bar soap, dish detergent, toothpaste, and medical disinfectants at levels of up to 2% and 0.3% (w/w), respectively. They are also formulated into carpets, toys, paints and building materials. Parabens are a group of compounds that exhibit antimicrobial activity, are stable over wide pH and temperature ranges, and are moderately soluble in water which make them ideal to use as have been extensively used as preservatives in a spectrum of products including lotions, face washes, facial creams, food stuffs, beverages, and industrial products due to their broad spectrum of antimicrobial activity, good stability over wide temperature and pH ranges, and moderate water solubility. Methyl paraben (MePB), ethyl paraben (EtPB), propyl paraben (PrPB), butyl paraben (BuPB) and benzyl paraben (BePB) are the mostly commonly used parabens. Parabens are found in more than 22,000 cosmetic products with levels up to 0.4% (by weight) for any individual paraben and 0.8% in combination. In pharmaceuticals, maximum paraben content may exceed 1%. Widespread use of antimicrobial chemicals resulted in widespread ubiquitous environmental occurrence and human exposure, resulting in theirallowing for frequent detections in diverse environmental matrices, including indoor dust, wastewater influent and effluent, surface water, and sewage sludge, and in biological matrices such as breast milk, serum, urine, cord blood and amniotic fluid.

Concerns over the potential risks of the above mentioned antimicrobial agents on human and animal health have been raised in the past decades. These compounds are considered as a group of emerging endocrine disruptors that cause immune dysfunction and affect human reproductive outcomes. Studies have shown their toxicities to aquatic organisms, such as algae, fish and invertebrates. Potential links have been suggested between human exposure to parabens and the etiology of breast cancer. There are also studies showing positive associations between the occurrence of antimicrobials and the detection frequency of antibiotic-resistance genes. In September 2016, the U.S. Food and Drug Administration (FDA) issued a final rule banning 19 antimicrobial ingredients including TCS and TCC, in over-the-counter (OTC) consumer antiseptic wash products, and the rule took effect starting from September 2017. With inadequate evaluation of the impact of these emerging contaminants on ecosystems and human health, it is necessary to keep monitoring their occurrence in the environment and levels of human exposure. In addition, continuous monitoring of the occurrence of these antimicrobials in the environment will assist in evaluating the effectiveness of certain regulatory practices.

In developed countries, people spend over 90% of their time in indoor environments, and the quality of the indoor environment has received increasing attention because of its implications for public health. Indoor dust is known to be a sink for semi-volatile organic compounds (SVOC) and particle-bound organic matter and thus has frequently been used as a matrix to assess indoor contamination and human indoor exposure. Exposure to contaminants in dust can occur via ingestion through direct contact with indoor dust and hand-to-mouth movements, as well as indirect contact as dust deposits on food or consumer products, which are later ingested. Inhalation and dermal absorption are also possible routes of exposure to contaminants deposited in dust. Children are the most susceptible population to contaminants in indoor dust, due to their rapidly developing organs and neurological system, greater intake of dust relative to body size and weight, and their activities on and in proximity to the floor, which leads to potentially elevated contact with contaminants.

So far, only a limited number of studies have reported the presence of parabens and TCS in indoor dust, and only one prior study worldwide has quantified TCC in dust. Due to their complex compositions, challenges exist for sensitive and accurate measurement of trace level contaminants in dust. In these studies, sample preparation often involves extraction followed by further cleanup, such as pressurized liquid extraction (PLE) with in-cell cleanup or accelerated solvent extraction (ASE) followed by SPE, matrix solid phase extraction (MSPD), pressurized hot water extraction (PHWE), and solvent extraction by mechanical shaking or sonication followed by solid phase extraction (SPE). Instrument analysis involves liquid chromatography-tandem mass spectrometry (LC-MS/MS), gas chromatography-mass spectrometry (GC-MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS). Although GC-MS or GC-MS/MS may have advantages on selectivity and sensitivity, they often require a pre-column derivatization step to make certain compounds suitable for GC analysis, which adds time and labor to an already cumbersome sample pretreatment.

In the past decades, modern sample preparation techniques such as QuEChERS (quick, easy, cheap, effective, rugged and safe) have been developed that require less organic solvent and are less time-consuming compared to the above mentioned sample preparation methods. The QuEChERS method is based on solvent extraction (normally utilizing acetonitrile) with an addition of salts to induce liquid-liquid partitioning, followed by a dispersive solid-phase extraction (d-SPE) for cleanup. The method was originally developed for extracting pesticides from fruits and vegetables, and later was modified and expanded to target a larger variety of chemicals in different matrices such as liver, urine and whole blood, sewage sludge, sediment, and drinking water treatment sludge. To the best of our knowledge, this method has not been used for the extraction of chemicals from indoor dust.