Microplastics in the Environment: Uptake, Bioaccumulation and Impacts on Plants, Animals and Humans Health: A Review

Microplastics (MPs), which are plastic particles smaller than 5 mm, have been generated due to the mismanagement and indiscriminate use of plastics over the past four decades, presenting a serious threat to ecosystems worldwide. MPs are universal and have been detected in all environmental compartments, including soil, air, groundwater, surface water, and oceans. They have also been detected in seafood (fish and shellfish), vegetables, poultry, terrestrial animals, mammals, and humans. Human exposure to MPs occurs through ingestion of contaminated food and drinking water, inhalation of microplastic-laden air, and dermal absorption via contaminated water, cosmetics, and personal care products (PCPs). Soil contamination by these particles primarily arises from the application of sewage sludge and bio-waste compost, plastic mulching, wastewater irrigation, landfill leachate, and atmospheric deposition. The presence of MPs in soil harms soil organic matter and bulk density, and alters microbial and bacterial activity. MPs reduce soil water retention capacity and decrease the availability of essential nutrients, such as nitrogen (N) andphosphorus (P). MPs’ adhere to root surfaces, retarding the uptake of water and nutrients by plants, thereby impeding plant growth and reducing crop productivity. In plants, MPs accumulation disrupts metabolic processes and decreases the amount of chlorophyll, resulting in decreased photosynthesis. MPs have been detected in various tissues of aquatic and terrestrial animals, including fish, seafood, birds, invertebrates, and mammals. Their accumulation induces behavioural changes, oxidative stress, inflammation, and adverse effects on reproductive and endocrine systems. In humans, bioaccumulation of microplastics is associated with gastrointestinal disturbances, respiratory disorders (including lung cancer), and dermal allergies, neurological disorders such as Parkinson's disease, Alzheimer's disease, and dementia, cardiovascular complications, and impaired reproductive health. The review highlights the detrimental effects of MPs on crop growth, aquatic organisms, terrestrial animals, and human health, emphasising the urgent need for effective mitigation and management strategies.