Feasibility studies on the uptake and bioaccessibility of pesticides, hormones and endocrine disruptive compounds in plants, and simulation of gastric and intestinal conditions

Highlights

• Plant uptake of environmental contaminants was monitored in soilless media.

• Dispersive liquid-liquid microextraction was used to preconcentrate analytes for GC-MS analysis.

• Matrix matching was used to enhance the accuracy of quantitative measurements.

• Concentration of analytes found in onion samples were in the range of 0.59–6.4 μg/g.

• The selected analytes were simulated under gastric and intestinal conditions to determine their stability.

Abstract

Large scale productions made by industries to meet the needs of the ever growing human population has led to the contamination of environmental resources such as water, air, soil and forests. These contaminants pose health risks to humans and they are capable of entering the food chain through aquatic organisms and by the uptake in plants. This study investigated the uptake of alkylphenols, hormones, pesticides and bisphenol A by plants grown in soilless media under laboratory conditions. Green onion and lettuce were selected for this purpose due to their high water intake rate. Optimum parameters of a dispersive liquid-liquid microextraction method were applied to aqueous samples to lower detection limits for the analytes determined by gas chromatography mass spectrometry. Analysis performed on the plant media on alternate days suggested migration of the analytes into the plants and this was confirmed by results (0.59–6.4 μg/g) obtained for analyzed plant samples at the end of the study. The plants were then treated in simulated gastric and intestinal conditions, and the results obtained suggested degradation of the analytes with time. This is the first comprehensive study on the migration of different environmental contaminants into plants and the changes they undergo when ingested into the stomach.

Introduction

Soil pollution is a common phenomenon that arises from several anthropogenic sources such as household and industrial wastes, mining wastes, accidental spill of petrol products, pesticide residues from agricultural applications and heavy metals from metal processing units [1]. Since most of these contaminants are artificially produced, they are usually non-biodegradable and they tend to be persistent in the environment, posing high toxicity risks to humans and other organisms [2]. Soil organisms such as earthworm are known to accumulate some contaminants while some bacteria strains have the capacity to degrade or breakdown contaminants such as pesticides [3]. Thus, specific microorganisms are isolated and modified to enhance the rate of degradation and consequent removal of specific contaminants [4]. Leaching of contaminants into groundwater could occur depending on factors such as contaminant solubility and type of soil [5]. Plant uptake of contaminants that remain in the soil depends greatly on the species of plant, interaction of soil microorganisms with the contaminant, temperature and physicochemical properties [6].

The rate of production and consumption of goods directly correlates with the level of contamination in the environment. Nonylphenol and octylphenol are two alkylphenols that have been of great environmental concern due to their ubiquitous distribution in the environment, arising from their use in several domestic and industrial products [7]. Bisphenol A is another chemical widely used in the production of materials such as plastics, food containers, dental and health care materials and kitchenware [8]. There are several studies that have reported on toxic effects of bisphenol A and alkyl phenols, including endocrine disruptive actions that lead to severe health disorders such as cancer [9], [10], [11], [12]. Since the early 1940s, commercial production of synthetic pesticides have increased tremendously due to the many benefits derived from their applications such as increased food quantity, need for food quality, long food storage period and prevention of vector borne diseases [13]. Despite these benefits, different toxic effects have been reported on several pesticides and this has led to the ban, restriction or regulation of all pesticides [14]. Organochlorine pesticides such as dieldrin, aldrin, α/β endosulfan, cis-chlordane and heptachlor are no longer approved for use [15] but due to their past applications in large quantity and their persistence, trace amounts can still be found in the environment. Organophosphate pesticides such as diazinon are less persistent than the organochlorine chemical class pesticides but they also pose health risks to humans and other organisms [16]. Estrone and 17-β-estradiol are natural steroidal estrogens that are naturally produced and excreted from women and animals. These estrogens can also be administered to augment hormone levels in menopause women undergoing hormonal replacement therapy [17]. These hormones are also widely distributed in the environment and have become a health concern due to reported cases of cancer risks in women [18].

Even though these contaminants occur at trace levels in the environment, advanced and sensitive analytical techniques such as gas chromatography tandem mass spectrometry (GC-MS/MS), gas chromatography high resolution mass spectrometry (GC–HRMS), atmospheric pressure chemical ionization gas chromatography triple quadrupole mass spectrometry (APCI/GC-MS/MS), liquid chromatography tandem mass spectrometry (LC-MS/MS) and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) are capable of performing ultratrace determinations of unknown compounds and metabolites [19], [20], [21], [22]. Gas chromatography mass spectrometry on the other hand does not have the sensitivity of the aforementioned techniques but this could be alleviated by employing microextraction techniques such as solid phase microextraction [23,24], hollow fiber liquid phase microextraction [25] and single drop microextraction [26]. Dispersive liquid-liquid microextraction is another preconcentration tool which is conveniently coupled with gas chromatography mass spectrometry for trace determination of analytes. It is a simple method that employs cost effective materials that result in high analyte enhancement factors and recoveries for the analytes from aqueous samples [27].

This study employed dispersive liquid-liquid microextraction as a preconcentration tool to investigate the feasibility of plant uptake of hormones, pesticides, alkylphenols and bisphenol A from a soilless media, and subsequent simulation of the plants under gastric and intestinal conditions.