Potential pulmonary effects of man-made organic fiber (MMOF) dusts

Assessment of pulmonary function and respiratory symptoms among INDIAN textile sizing mill workers

BACKGROUND

Textile-sizing mill workers are exposed to various hazards in the sizing units during their working hours and are at risk of acquiring lung impairments due to the usage of sizing chemicals in the sizing process.

OBJECTIVE

The main aim of this study is to assess the influence of cotton dust and sizing agents on lung function and breathing difficulties among Indian textile sizing mill workers.

METHODS

This cross-sectional study was carried out at a textile-sizing mill from August 2022 to September 2022. A modified questionnaire based American Thoracic Society's standard was used to assess respiratory symptoms among sizing mill workers and the pulmonary function test was conducted Spirometry. The chi-square test was used to find the difference between respiratory symptoms and the t-test was used to find the difference between spirometric parameters.

RESULTS

Textile sizing mill workers showed significant (P <  0.0001) decline in peak expiratory flow rate, forced vital capacity (FVC), ratio of FEV1 and forced vital capacity, and forced expiratory volume in 1 s (FEV1). There was an association between symptoms and duration of exposure to pulmonary abnormality. Sizing mill workers showed a significant decline in lung functions and an increase in pulmonary symptoms. As the service duration of exposure in terms of years increased, respiratory symptoms increased and spirometric abnormality also increased.

CONCLUSION

This study confirms that sizing agents such as polyvinyl alcohol (PVA), emulsifier, wax, carboxymethyl cellulose (CMC), and starch used in sizing mills are also responsible for respiratory illness and lung impairment among textile workers.

Micro- and nano-plastics in the atmosphere: A review of occurrence, properties and human health risks

The ubiquitous occurrence of micro/nano plastics (MNPs) poses potential threats to ecosystem and human health that have attracted broad concerns in recent decades. Detection of MNPs in several remote regions has implicated atmospheric transport as an important pathway for global dissemination of MNPs and hence as a global health risk. In this review, the latest research progress on (1) sampling and detection; (2) origin and characteristics; and (3) transport and fate of atmospheric MNPs was summarized. Further, the current status of exposure risks and toxicological effects from inhaled atmospheric MNPs on human health is examined. Due to limitations in sampling and identification methodologies, the study of atmospheric nanoplastics is very limited today. The large spatial variation of atmospheric MNP concentrations reported worldwide makes it difficult to compare the overall indoor and outdoor exposure risks. Several in vitro, in vivo, and epidemiological studies demonstrate adverse effects of immune response, apoptosis and oxidative stress caused by MNP inhalation that may induce cardiovascular diseases and reproductive and developmental abnormalities. Given the emerging importance of atmospheric MNPs, the establishment of standardized sampling-pretreatment-detection protocols and comprehensive toxicological studies are critical to advance environmental and health risk assessments of atmospheric MNPs.

Potential of lignocellulosic fiber reinforced polymer composites for automobile parts production: Current knowledge, research needs, and future direction

In recent years, there has been a notable surge in research focusing on the use of natural fiber-reinforced polymer composites (NFRPCs) in the automobile industry. These materials offer several advantages over their synthetic counterparts, including lightweight properties, renewability, cost-effectiveness, and environmental friendliness. This increasing research interest in NFRPCs within the automotive sector is primarily aimed at overcoming the challenges that have thus far limited their industrial applications when compared to conventional synthetic composites. This paper provides a comprehensive overview of the potential applications and sustainability of lignocellulosic-based NFRPCs in the automobile industry. It examines the current state of knowledge, identifies research needs and existing limitations, and provides insights into future perspectives. This review shows that, while lignocellulosic fibers hold great promise as sustainable, high-performance, and cost-effective alternatives to traditional reinforcing fibers, continuous research is needed to further address issues such as fiber-matrix compatibility, processing techniques, long-term durability concerns, and general property improvement. These advancements are essential to meet the increasing performance demand for eco-friendly, renewable, and energy-efficient materials in automotive design.

A comprehensive review on the source, ingestion route, attachment and toxicity of microplastics/nanoplastics in human systems

Microplastics (MPs)/nanoplastics (NPs) are widely found in the natural environment, including soil, water and the atmosphere, which are essential for human survival. In the recent years, there has been a growing concern about the potential impact of MPs/NPs on human health. Due to the increasing interest in this research and the limited number of studies related to the health effects of MPs/NPs on humans, it is necessary to conduct a systematic assessment and review of their potentially toxic effects on human organs and tissues. Humans can be exposed to microplastics through ingestion, inhalation and dermal contact, however, ingestion and inhalation are considered as the primary routes. The ingested MPs/NPs mainly consist of plastic particles with a particle size ranging from 0.1 to 1 μm, that distribute across various tissues and organs within the body, which in turn have a certain impact on the nine major systems of the human body, especially the digestive system and respiratory system, which are closely related to the intake pathway of MPs/NPs. The harmful effects caused by MPs/NPs primarily occur through potential toxic mechanisms such as induction of oxidative stress, generation of inflammatory responses, alteration of lipid metabolism or energy metabolism or expression of related functional factors. This review can help people to systematically understand the hazards of MPs/NPs and related toxicity mechanisms from the level of nine biological systems. It allows MPs/NPs pollution to be emphasized, and it is also hoped that research on their toxic effects will be strengthened in the future.

The potential impacts of micro-and-nano plastics on various organ systems in humans

Humans are exposed to micro-and-nano plastics (MNPs) through various routes, but the adverse health effects of MNPs on different organ systems are not yet fully understood. This review aims to provide an overview of the potential impacts of MNPs on various organ systems and identify knowledge gaps in current research. The summarized results suggest that exposure to MNPs can lead to health effects through oxidative stress, inflammation, immune dysfunction, altered biochemical and energy metabolism, impaired cell proliferation, disrupted microbial metabolic pathways, abnormal organ development, and carcinogenicity. There is limited human data on the health effects of MNPs, despite evidence from animal and cellular studies. Most of the published research has focused on specific types of MNPs to assess their toxicity, while other types of plastic particles commonly found in the environment remain unstudied. Future studies should investigate MNPs exposure by considering realistic concentrations, dose-dependent effects, individual susceptibility, and confounding factors.

Worker studies suggest unique liver carcinogenicity potential of polyvinyl chloride microplastics

BACKGROUND

Plastic debris pervades our environment. Some breaks down into microplastics (MPs) that can enter and distribute in living organisms causing effects in multiple target organs. MPs have been demonstrated to harm animals through environmental exposure. Laboratory animal studies are still insufficient to evaluate human impact. And while MPs have been found in human tissues, the health effects at environmental exposure levels are unclear.

AIM

We reviewed and summarized existing evidence on health effects from occupational exposure to MPs. Additionally, the diverse effects documented for workers were organized by MP type and associated co-contaminants. Evidence of the unique effects of polyvinyl chloride (PVC) on liver was then highlighted.

METHODS

We conducted two stepwise online literature reviews of publications focused on the health risks associated with occupational MP exposures. This information was supplemented with findings from animal studies.

RESULTS

Our analysis focused on 34 published studies on occupational health effects from MP exposure with half involving exposure to PVC and the other half a variety of other MPs to compare. Liver effects following PVC exposure were reported for workers. While PVC exposure causes liver toxicity and increases the risk of liver cancers, including angiosarcomas and hepatocellular carcinomas, the carcinogenic effects of work-related exposure to other MPs, such as polystyrene and polyethylene, are not well understood.

CONCLUSION

The data supporting liver toxicity are strongest for PVC exposure. Overall, the evidence of liver toxicity from occupational exposure to MPs other than PVC is lacking. The PVC worker data summarized here can be useful in assisting clinicians evaluating exposure histories from PVC exposure and designing future cell, animal, and population exposure-effect research studies.

From oceans to dinner plates: The impact of microplastics on human health

Microplastics, measuring less than 5 mm in diameter, are now found in various environmental media, including soil, water, and air, and have infiltrated the food chain, ultimately becoming a part of the human diet. This study offers a comprehensive examination of the intricate nexus between microplastics and human health, thereby contributing to the existing knowledge on the subject. Sources of microplastics, including microfibers from textiles, personal care products, and wastewater treatment plants, among others, were assessed. The study meticulously examined the diverse routes of microplastic exposure-ingestion, inhalation, and dermal contact-offering insights into the associated health risks. Notably, ingestion of microplastics has been linked to gastrointestinal disturbances, endocrine disruption, and the potential transmission of pathogenic bacteria. Inhalation of airborne microplastics emerges as a critical concern, with possible implications for respiratory and cardiovascular health. Dermal contact, although less explored, raises the prospect of skin irritation and allergic reactions. The impacts of COVID-19 on microplastic pollution were also highlighted. Throughout the manuscript, the need for a deeper mechanistic understanding of microplastic interactions with human systems is emphasized, underscoring the urgency for further research and public awareness.

C-Reactive Protein: Pathophysiology, Diagnosis, False Test Results and a Novel Diagnostic Algorithm for Clinicians

The current literature provides a body of evidence on C-Reactive Protein (CRP) and its potential role in inflammation. However, most pieces of evidence are sparse and controversial. This critical state-of-the-art monography provides all the crucial data on the potential biochemical properties of the protein, along with further evidence on its potential pathobiology, both for its pentameric and monomeric forms, including information for its ligands as well as the possible function of autoantibodies against the protein. Furthermore, the current evidence on its potential utility as a biomarker of various diseases is presented, of all cardiovascular, respiratory, hepatobiliary, gastrointestinal, pancreatic, renal, gynecological, andrological, dental, oral, otorhinolaryngological, ophthalmological, dermatological, musculoskeletal, neurological, mental, splenic, thyroid conditions, as well as infections, autoimmune-supposed conditions and neoplasms, including other possible factors that have been linked with elevated concentrations of that protein. Moreover, data on molecular diagnostics on CRP are discussed, and possible etiologies of false test results are highlighted. Additionally, this review evaluates all current pieces of evidence on CRP and systemic inflammation, and highlights future goals. Finally, a novel diagnostic algorithm to carefully assess the CRP level for a precise diagnosis of a medical condition is illustrated.

A review of potential human health impacts of micro- and nanoplastics exposure

This systematic review aims to summarize the current knowledge on biological effects of micro- and nanoplastics (MNPs) on human health based on mammalian systems. An extensive search of the literature led to a total of 133 primary research articles on the health relevance of MNPs. Our findings revealed that although the study of MNP cytotoxicity and inflammatory response represents a major research theme, most studies (105 articles) focused on the effects of polystyrene MNPs due to their wide availability as a well characterised research material that can be manufactured with a large range of particle sizes, fluorescence labelling as well as various surface modifications. Among the 133 studies covered in this review, 117 articles reported adverse health effects after being exposed to MNPs. Mammalian in vitro studies identified multiple biological effects including cytotoxicity, oxidative stress, inflammatory response, genotoxicity, embryotoxicity, hepatotoxicity, neurotoxicity, renal toxicity and even carcinogenicity, while rodent in vivo models confirmed the bioaccumulation of MNPs in the liver, spleen, kidney, brain, lung and gut, presenting adverse effects at different levels including reproductive toxic effects and trans-generational toxicity. In contrast, the remaining 16 studies indicated an insignificant impact of MNPs on humans. A few studies attempted to investigate the mechanisms or factors driving the toxicity of MNPs and identified several determining factors including size, concentration, shape, surface charge, attached pollutants and weathering process, which, however, were not benchmarked or considered by most studies. This review demonstrates that there are still many inconsistencies in the evaluation of the potential health effects of MNPs due to the lack of comparability between studies. Current limitations hindering the attainment of reproducible conclusions as well as recommendations for future research directions are also presented.

International quantification of microplastics in indoor dust: prevalence, exposure and risk assessment

This international scale study measured the prevalence of indoor microplastics (MPs) in deposited dust in 108 homes from 29 countries over a 1-month period. Dust borne MPs shape, colour, and length were determined using microscopy and the composition measured using μFTIR. Human health exposure and risk was assessed along with residential factors associated with MPs via a participant questionnaire. Samples were categorised according to each country's gross national income (GNI). Synthetic polymers dominated in low income (LI) (39%) and high income (HI) (46%) while natural fibres were the most prevalent in medium income (MI) (43%) countries. Composition and statistical analysis showed that the main sources of MPs and dust were predominantly from indoor sources. Across all GNI countries, greater vacuuming frequency was associated with lower MPs loading. High income country samples returned higher proportions of polyamides and polyester fibres, whereas in LI countries polyurethane was the most prominent MPs fibre. Exposure modelling showed infants (0-2 years) were exposed to the highest MPs dose through inhalation (4.5 × 10^-5 ± 3 × 10^-5) and ingestion (3.24 × 10^-2 ± 3.14 × 10^-2) mg/kg-B_w/day. Health risk analysis of constituent monomers of polymers indicates cancer incidence was estimated at 4.1-8.7 per million persons across age groups. This study's analysis showed socio-economic factors and age were dominant variables in determining dose and associated health outcomes of MPs in household dust.

First evidence of microplastics isolated in European citizens' lower airway

Microplastics (MPs) have been detected in all environmental locations, including the atmosphere. However, few studies have investigated the presence of airborne MPs in the human respiratory system. Our research purpose was to investigate these pollutants in the lower human airways of 44 adult European citizens, using bronchoalveolar lavage fluid (BALF) collection as a minimally invasive method, that enables the detection of these pollutants in living patients. We studied the relationship between the patients' life habits and physiological parameters, based on background information and medical and occupational history, and the concentration of MPs isolated from their respiratory systems. Our results indicate that most MPs were in the form of microfibers (MFs) (97.06%), with an average concentration of 9.18 ± 2.45 items/100 mL BALF, and only 5.88% (0.57 ± 0.27 items/100 mL BALF) were particulate MPs, without a significant relationship with environmental, physiological, or clinical factors. The average size was 1.73 ± 0.15 mm, with the longest dimension (9.96 mm) corresponding to a polyacrylic fiber. Taken together, the results demonstrated the occurrence of MPs in the lower human airway, although more studies are necessary to elucidate the negative effects these pollutants could induce in the human respiratory system and its associated diseases.

A Review on Synthetic Fibers for Polymer Matrix Composites: Performance, Failure Modes and Applications

In the last decade, synthetic fiber, as a reinforcing specialist, has been mainly used in polymer matrix composites (PMC’s) to provide lightweight materials with improved stiffness, modulus, and strength. The significant feature of PMC’s is their reinforcement. The main role of the reinforcement is to withstand the load applied to the composite. However, in order to fulfill its purpose, the reinforcements must meet some basic criteria such as: being compatible with the matrix, making chemical or adhesion bonds with the matrix, having properties superior to the matrix, presenting the optimal orientation in composite and, also, having a suitable shape. The current review reveals a detailed study of the current progress of synthetic fibers in a variety of reinforced composites. The main properties, failure modes, and applications of composites based on synthetic fibers are detailed both according to the mentioned criteria and according to their types (organic or inorganic fibers). In addition, the choice of classifications, applications, and properties of synthetic fibers is largely based on their physical and mechanical characteristics, as well as on the synthesis process. Finally, some future research directions and challenges are highlighted.

Characteristics and influencing factors of airborne microplastics in nail salons

Airborne microplastic particles (MPs) are emerging contaminants. Although some studies have investigated the characteristics of indoor MPs in homes or offices, information regarding MPs in nail salons with potentially higher MP pollution is unavailable. In this study, we collected indoor and outdoor air samples from nail salons to analyze the concentrations, physical characteristics, and polymers of MPs and further assessed the exposure through inhalation and influencing factors. Our data displayed that the average indoor MP concentration was 46 ± 55 MPs/m³. The estimated average annual exposure to indoor MPs was 67,567 ± 81,782 MPs/year. The predominant shape and size of indoor MPs were fragment and <50 μm, respectively. The predominant polymer in indoor air was acrylic (27%), followed by rubber (21%), and polyurethane (13%). Air conditioner, nail treatment, ceiling and flooring with plastic materials, and number of occupants were factors affecting indoor MP concentrations. We concluded that MP pollution was more severe in nail salons and the physical characteristics and polymer compositions differed between nail salons and other indoor spaces reported in other studies. Air conditioner usage induced higher MP emission, and higher MP concentrations were observed in nail salons with plastic ceiling and flooring or more occupants.

Air conditioner filters become sinks and sources of indoor microplastics fibers

Indoor airborne microplastics fibers (MPFs) are emerging contaminants of growing concern. Nowadays, air conditioners (ACs) are widely used in indoor environments. However, little is known about their impact on the distribution of indoor MPFs. In this study, we first disclosed the prevalence of MPF contamination in filters for indoor split ACs used in living rooms, dormitories, and offices. The average density of microfibers was 1.47-21.4 × 10² items/cm², and a total 27.7-35.0% of fibers were MPFs. Of these fibers, the majority were polyester (45.3%), rayon (27.8%), and cellophane (20.1%). We further tracked the long-term accumulation of MPFs on AC filters in three types of rooms, and demonstrated that dormitories showed relatively heavy accumulation especially after running for 35-42 days. Furthermore, we found that simulative AC filters which had been lined with PET MPFs could effectively release those MPFs into indoor air, propelling them away from the ACs at varying distances. Statistical analysis showed that the estimated daily intake of MPFs (5-5000 μm length) from AC filters would increase gradually with their usage, with the intake volume reaching up to 11.2 ± 2.2-44.0 ± 8.9 items/kg-BW/day by the 70th day, although this number varied among people of different ages. Altogether, these findings suggest that AC filters can act as both a sink and a source of microplastics fibers. Therefore, AC filters should be evaluated not only for their substantial impact on the distribution of indoor airborne MPFs, but also for their role in the prevalence of the related health risks.

Co-production of future scenarios of policy action plans in a science-policy-industry interface - The case of microfibre pollution from waste water treatment plants in Norway

One of the ambitions of the UN Decade of Ocean Science is stakeholder interaction to co-produce new ideas and solutions for policy action plans to ensure that environmental challenges are mitigated in a timely manner. Regulations around the release of microfibres are largely lacking, and we are at an excellent point of departure to test integrative methods of such co-production. We co-designed conceptual maps and Bayesian Belief Networks with probabilistic future scenarios within both inter- and intra-sectoral workshops with industry and scientific stakeholders to gain comparable results of policy action scenarios for curbing the challenge of microfibre pollution within this context. We found that when scientists worked on this alone, their focus was different than when working together with industry directly. Scientists focused on methods for avoiding release into the environment from a technical vantage point, whereas industry emphasized regulatory requirements needed to avoid ambiguity within the sector.

Airborne Microplastic Concentrations in Five Megacities of Northern and Southeast China

Airborne microplastics (MPs) are receiving increasing attention due to their ubiquitous nature and the potential human health consequences resulting from inhalation. The limited data for airborne MP concentrations vary widely among studies (∼4 orders of magnitude), but comparisons are tenuous due to the inconsistent collection and detection/enumeration methodologies among studies. Herein, we used uniform methodologies to obtain comparable airborne MP concentration data to assess MP exposure intensity in five Chinese megacities. Airborne MP concentrations in northern cities (358 ± 132 items/m³) were higher than those in southeast cities (230 ± 94 items/m³) but of a similar order of magnitude, unlike previous studies. The majority (94.7%) of MPs found in air samples were smaller than 100 μm, and the main shape of airborne MPs was fragments (88.2%). Polyethylene, polyester, and polystyrene were the dominant polymers comprising airborne MPs. No consistent relationships were detected between airborne MP concentration and typical socioeconomic indices, and the spatial and diurnal patterns for airborne MPs were different from various components of air quality indices (PM_2.5, PM₁₀, etc.). These findings reflect the contrasting source/generation dynamics between airborne MPs and other airborne pollutants. Maximum annual exposure of humans to airborne MPs was estimated in the range of 1-2 million/year in these megacities, highlighting the need for additional research examining the human health risks from the inhalation of airborne MPs.

Evidence from in vitro and in vivo studies on the potential health repercussions of micro- and nanoplastics

Plastic is a synthetic or semisynthetic polymer with numerous physicochemical properties, and its fragmentation can give rise to microplastics (MPs) and nanoplastics (NPs). These particles can enter our ecosystem, where a process of constant degradation facilitates their dispersion and absorption by different species, affecting multiple organs and systems. The objective of this review was to provide an update on the potential health effects of MPs and NPs indicated by in vitro and in vivo studies. In vitro studies have described the absorption of plastic particles of different sizes and have documented their proinflammatory effects and genotoxicity, which can lead to the structural alteration of cells. MPs and NPs have also been implicated in the development of antibiotic resistance. In vivo studies have demonstrated that MPs and NPs can access organisms via dietary and respiratory pathways and through the epidermis. Their reported effects include: changes in microbiota and digestive enzyme production; inflammatory processes at respiratory level; circulatory and reproductive system disorders; and neurotoxicity, inducing behavioral changes. In vitro and in vivo studies have evidenced detrimental effects in different organs and systems as a function of the dose, size, and chemical properties of plastic particles. Further research is warranted to determine the effects on human health of these particles at environmental doses.

Microplastics in the Environment: Intake through the Food Web, Human Exposure and Toxicological Effects

Recently, studies on microplastics (MPs) have increased rapidly due to the growing awareness of the potential health risks related to their occurrence. The first part of this review is devoted to MP occurrence, distribution, and quantification. MPs can be transferred from the environment to humans mainly through inhalation, secondly from ingestion, and, to a lesser extent, through dermal contact. As regards food web contamination, we discuss the microplastic presence not only in the most investigated sources, such as seafood, drinking water, and salts, but also in other foods such as honey, sugar, milk, fruit, and meat (chickens, cows, and pigs). All literature data suggest not-negligible human exposure to MPs through the above-mentioned routes. Consequently, several research efforts have been devoted to assessing potential human health risks. Initially, toxicological studies were conducted with aquatic organisms and then with experimental mammal animal models and human cell cultures. In the latter case, toxicological effects were observed at high concentrations of MPs (polystyrene is the most common MP benchmark) for a short time. Further studies must be performed to assess the real consequences of MP contamination at low concentrations and prolonged exposure.

Airborne microplastics in indoor and outdoor environments of a coastal city in Eastern China

Microplastics (MPs) in marine and terrestrial environments have been intensively studied, but the dynamics of airborne MPs remains limited. Existing studies on atmospheric MPs are mostly derived from collection of atmospheric deposition, whereas direct measurements of airborne MPs are scarce. However, the abundance of airborne MPs is more relevant for evaluating human inhalation exposure risk. Herein, airborne MPs in indoor and outdoor environments from urban and rural areas of a coastal city in eastern China were investigated. MP concentrations (mean±SD) in indoor air (1583 ± 1180 n/m³) were an order of magnitude higher than outdoor air (189 ± 85 n/m³), and airborne MP concentrations in urban areas (224 ± 70 n/m³) were higher than rural areas (101 ± 47 n/m³). MPs smaller than 100 µm dominated airborne MPs, and the predominant shape of airborne MPs was fragments, as opposed to fibers. The larger MP size fractions contained a higher proportion of fibers, whereas the smaller size fractions were nearly exclusively composed of fragments. The health risk caused by ubiquitous airborne MPs should not be discounted as the maximum annual outdoor exposure of airborne MPs can reach 1 million/year, while indoor exposure may be even higher due to higher indoor airborne MP concentrations.

Presence of airborne microplastics in human lung tissue

Plastics are ubiquitously used by societies, but most of the plastic waste is deposited in landfills and in the natural environment. Their degradation into submillimetre fragments, called microplastics, is a growing concern due to potential adverse effects on the environment and human health. Microplastics are present in the air and may be inhaled by humans, but whether they have deleterious effects on the respiratory system remain unknown. In this study, we determined the presence of microplastics in human lung tissues obtained at autopsies. Polymeric particles (n = 33) and fibres (n = 4) were observed in 13 of 20 tissue samples. All polymeric particles were smaller than 5.5 µm in size, and fibres ranged from 8.12 to 16.8 µm. The most frequently determined polymers were polyethylene and polypropylene. Deleterious health outcomes may be related to the heterogeneous characteristics of these contaminants in the respiratory system following inhalation.

Does microplastic really represent a threat? A review of the atmospheric contamination sources and potential impacts

Microplastics (MPs) are regarded as one of the major atmospheric contaminants that have gained wide attention across the globe in the current dispensation. Airborne MPs have been collected in atmospheric fallouts, in indoor and outdoor air as well as along roadways and indoor dust. The most dominating constituent shapes and forms of identified airborne MPs are fibers and synthetic textiles, respectively. With the breathing mechanism as a spontaneous practice for survival, the inhalation of airborne MPs is an inevitable deal. The level of toxicity of MPs to organisms stems from its physiochemical speciation. The smaller size and almost weightless nature make it possible to suspend in the atmosphere and be inhaled and create potential health problems. Nonetheless, the data available concerning the presence of airborne MPs and its environmental and human health impacts is limited. In this review, we extensively discuss the rigorous and suitable methodologies adopted for the analysis of airborne MPs in previous studies. The characteristics and sources of airborne MPs, the potential health impacts on humans, and some mitigating measures have also been discussed thoroughly.

A review of data for quantifying human exposures to micro and nanoplastics and potential health risks

Plastic debris have been shown to degenerate to particle sizes that can be transported in air, water, and food. Small particles are documented to enter and exit our bodies and translocate to and from some internal organs. Health effects on respiratory, hepatic, immune, and gastrointestinal systems have been reported in humans and other mammals in response to elevated particle or fiber exposures. These health effects differed by plastic type and size, and there was evidence of dose response for a few health endpoints. We conducted a systematic word search and reviewed published literature to identify microplastic and nanoplastic studies that quantified exposure via the ingestion, inhalation, and subcutaneous absorption (not dermal) exposure pathways; identified translocation, internal dose, and associations with health effects and markers related to exposures to specific sizes and types of plastics. We identified the data gaps in relating exposure data to health effects and biomarkers, most notably the lack of characterization of plastic particles and fibers smaller than 10 μm in most media.

An emerging class of air pollutants: Potential effects of microplastics to respiratory human health?

It is increasingly recognized that the ubiquity of convenient single-use plastic has resulted in a global plastic pollution challenge, with substantial environmental and health consequences. Physical, chemical, and biological processes result in plastic weathering, with eventual formation of debris in the micro to nano size range. There is an increasing awareness that plastic fragments are dispersed in the air and can be inhaled by humans, which may cause adverse effects on the respiratory system and on other systems. Urban environments are often characterized by high concentrations of fine airborne dust from various sources. To date, however, there is limited information on the distribution, shape, and size of microplastics in the air in urban and other environments. In this article, we review and discuss our current understanding of the exposure characteristics of airborne plastic debris in urbanized areas, focusing on concentration, size, morphology, presence of additives and distributions of different polymers. The natural and extend data are compiled and compared to laboratory-based analyses to further our understanding of the potential adverse effects of inhaled plastic particles on human health.

Occupational exposure to carbon fibers impregnated with epoxy resins and evaluation of their respirability

Objectives: The study aims to investigate occupational exposure to carbon fibers impregnated with epoxy resins (carbon fiber reinforced [CFR]) in workers at an airplane fuselage section construction plant, by environmental and biological monitoring.Materials and methods: Determination of airborne CFR was done by environmental sampling with active samplers, 11 of which were stationary and 19 personal samplings. The subsequent analyses were performed in the scanning electron microscope fitted with an X-ray microanalysis system (SEM-EDXA). Biological monitoring was carried out by determining CFR in exhaled breath condensate (EBC) collected from 19 male workers who wore personal environmental samplers (exposed workers) and from 10 male workers at the same factory who had no occupational exposure to CFR (internal controls). CFR analysis was done by SEM, applying the method used for determining asbestos fibers in aqueous samples.Results: The airborne CFR concentrations were found to be significantly higher (p = 0.03) at personal samplings (median value 7.01 ff/L, range 1.24-11.16 ff/L) than stationary samplings (median value 1.93 ff/L, range 0.55-10.09 ff/L). The aerodynamic diameters calculated starting from the length and geometric diameter of the sampled CFRs were always higher than 20 µm. CFR was not found in any of the EBC samples collected from the exposed workers and controls.Conclusions: Despite the evidence of occupational exposure to low concentrations of CFR, the absence of such fibers in the EBC in the exposed workers confirms their non-respirability, as expected based on their aerodynamic diameter.

Widespread distribution of PET and PC microplastics in dust in urban China and their estimated human exposure

Dust is a fate of many contaminants and may be an important medium for the human exposure to these contaminants. Microplastics (MPs) have been observed in dust in previous studies. However, the mass concentrations of dominant MPs in dust and the exposure risk to human remain unclear. In this study, indoor and outdoor dust samples were collected from 39 major cities of China. The mass concentrations of polyethylene terephthalate (PET) and polycarbonate (PC) MPs were determined through alkali-assisted thermal depolymerization-liquid chromatography-tandem mass spectrometry, and the shape and component distribution of MPs were analyzed by optical microscopy and micro-Fourier transform infrared spectroscopy. PET MPs were detected in all the samples at high concentrations of 1550-120,000 mg/kg (indoor) and 212-9020 mg/kg (outdoor) and PC MPs were detected in approximately 70% of the samples, with median concentrations of 4.6 mg/kg (indoor) and 2.0 mg/kg (outdoor). Fiber was the main shape of suspected MPs, and polyester (including PET) was identified as an important component in MPs from dust. Indoor dust is a non-negligible source of human exposure to MPs, accounting for a geomean daily intake of 17,300 ng/kg-bw of PET MPs in children.

Simulating human exposure to indoor airborne microplastics using a Breathing Thermal Manikin

Humans are potentially exposed to microplastics through food, drink, and air. The first two pathways have received quite some scientific attention, while little is known about the latter. We address the exposure of humans to indoor airborne microplastics using a Breathing Thermal Manikin. Three apartments were investigated, and samples analysed through FPA-µFTIR-Imaging spectroscopy followed by automatic analyses down to 11 µm particle size. All samples were contaminated with microplastics, with concentrations between 1.7 and 16.2 particles m-3. Synthetic fragments and fibres accounted, on average, for 4% of the total identified particles, while nonsynthetic particles of protein and cellulose constituted 91% and 4%, respectively. Polyester was the predominant synthetic polymer in all samples (81%), followed by polyethylene (5%), and nylon (3%). Microplastics were typically of smaller size than nonsynthetic particles. As the identified microplastics can be inhaled, these results highlight the potential direct human exposure to microplastic contamination via indoor air.

Plastic pollution and potential solutions

A review is presented of the manufacture and use of different types of plastic, and the effects of pollution by these materials on animal, human and environmental health, insofar as this is known. Since 2004, the world has made as much plastic as it did in the previous half century, and it has been reckoned that the total mass of virgin plastics ever made amounts to 8.3 billion tonnes, mainly derived from natural gas and crude oil, used as chemical feedstocks and fuel sources. Between 1950 and 2015, a total of 6.3 billion tonnes of primary and secondary (recycled) plastic waste was generated, of which around 9% has been recycled, and 12% incinerated, with the remaining 79% either being stored in landfills or having been released directly into the natural environment. In 2015, 407 million tonnes (Mt) of plastic was produced, of which 164 Mt was consumed by packaging (36% of the total). Although quoted values vary, packaging probably accounts for around one third of all plastics used, of which approximately 40% goes to landfill, while 32% escapes the collection system. It has been deduced that around 9 Mt of plastic entered the oceans in 2010, as a result of mismanaged waste, along with up to 0.5 Mt each of microplastics from washing synthetic textiles, and from the abrasion of tyres on road surfaces. However, the amount of plastics actually measured in the oceans represents less than 1% of the (at least) 150 Mt reckoned to have been released into the oceans over time. Plastic accounts for around 10% by mass of municipal waste, but up to 85% of marine debris items - most of which arrive from land-based sources. Geographically, the five heaviest plastic polluters are P. R. China, Indonesia, Philippines, Vietnam and Sri Lanka, which between them contribute 56% of global plastic waste. Larger, primary plastic items can undergo progressive fragmentation to yield a greater number of increasingly smaller 'secondary' microplastic particles, thus increasing the overall surface area of the plastic material, which enhances its ability to absorb, and concentrate, persistent organic pollutants (POPs) such as dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs), with the potential to transfer them to the tissues of animals that ingest the microplastic particles, particularly in marine environments. Although fears that such microparticles and their toxins may be passed via food webs to humans are not as yet substantiated, the direct ingestion of microplastics by humans via drinking water is a distinct possibility - since 92% of samples taken in the USA and 72% in Europe showed their presence - although any consequent health effects are as yet unclear. Foodstuffs may also become contaminated by microplastics from the air, although any consequent health effects are also unknown. In regard to such airborne sources, it is noteworthy that small plastic particles have been found in human lung tissue, which might prove an adverse health issue under given circumstances. It is also very striking that microplastics have been detected in mountain soils in Switzerland, which are most likely windborne in origin. Arctic ice core samples too have revealed the presence of microplastics, which were most likely carried on ocean currents from the Pacific garbage patch, and from local pollution from shipping and fishing. Thus, sea ice traps large amounts of microplastics and transports them across the Arctic Ocean, but these particles will be released into the global environment when the ice melts, particularly under the influence of a rising mean global temperature. While there is a growing emphasis toward the substitution of petrochemically derived plastics by bioplastics, controversy has arisen in regard to how biodegradable the latter actually are in the open environment, and they presently only account for 0.5% of the total mass of plastics manufactured globally. Since the majority of bioplastics are made from sugar and starch materials, to expand their use significantly raises the prospect of competition between growing crops to supply food or plastics, similarly to the diversion of food crops for the manufacture of primary biofuels. The use of oxo-plastics, which contain additives that assist the material to degrade, is also a matter of concern, since it is claimed that they merely fragment and add to the environmental burden of microplastics; hence, the European Union has moved to restrict their use. Since 6% of the current global oil (including natural gas liquids, NGLs) production is used to manufacture plastic commodities - predicted to rise to 20% by 2050 - the current approaches for the manufacture and use of plastics (including their end-use) demand immediate revision. More extensive collection and recycling of plastic items at the end of their life, for re-use in new production, to offset the use of virgin plastic, is a critical aspect both for reducing the amount of plastic waste entering the environment, and in improving the efficiency of fossil resource use. This is central to the ideology underpinning the circular economy, which has common elements with permaculture, the latter being a regenerative design system based on 'nature as teacher', which could help optimise the use of resources in town and city environments, while minimising and repurposing 'waste'. Thus, food might be produced more on the local than the global scale, with smaller inputs of fuels (including transportation fuels for importing and distributing food), water and fertilisers, and with a marked reduction in the use of plastic packaging. Such an approach, adopted by billions of individuals, could prove of immense significance in ensuring future food security, and in reducing waste and pollution - of all kinds.

Plastic and Human Health: A Micro Issue?

Microplastics are a pollutant of environmental concern. Their presence in food destined for human consumption and in air samples has been reported. Thus, microplastic exposure via diet or inhalation could occur, the human health effects of which are unknown. The current review article draws upon cross-disciplinary scientific literature to discuss and evaluate the potential human health impacts of microplastics and outlines urgent areas for future research. Key literature up to September 2016 relating to accumulation, particle toxicity, and chemical and microbial contaminants was critically examined. Although microplastics and human health is an emerging field, complementary existing fields indicate potential particle, chemical and microbial hazards. If inhaled or ingested, microplastics may accumulate and exert localized particle toxicity by inducing or enhancing an immune response. Chemical toxicity could occur due to the localized leaching of component monomers, endogenous additives, and adsorbed environmental pollutants. Chronic exposure is anticipated to be of greater concern due to the accumulative effect that could occur. This is expected to be dose-dependent, and a robust evidence-base of exposure levels is currently lacking. Although there is potential for microplastics to impact human health, assessing current exposure levels and burdens is key. This information will guide future research into the potential mechanisms of toxicity and hence therein possible health effects.

Transformation of the released asbestos, carbon fibers and carbon nanotubes from composite materials and the changes of their potential health impacts

Composite materials with fibrous reinforcement often provide superior mechanical, thermal, electrical and optical properties than the matrix. Asbestos, carbon fibers and carbon nanotubes (CNTs) have been widely used in composites with profound impacts not only on technology and economy but also on human health and environment. A large number of studies have been dedicated to the release of fibrous particles from composites. Here we focus on the transformation of the fibrous fillers after their release, especially the change of the properties essential for the health impacts. Asbestos fibers exist in a large number of products and the end-of-the-life treatment of asbestos-containing materials poses potential risks. Thermal treatment can transform asbestos to non-hazardous phase which provides opportunities of safe disposal of asbestos-containing materials by incineration, but challenges still exist. Carbon fibers with diameters in the range of 5–10 μm are not considered to be respirable, however, during the release process from composites, the carbon fibers may be split along the fiber axis, generating smaller and respirable fibers. CNTs may be exposed on the surface of the composites or released as free standing fibers, which have lengths shorter than the original ones. CNTs have high thermal stability and may be exposed after thermal treatment of the composites and still keep their structural integrity. Due to the transformation of the fibrous fillers during the release process, their toxicity may be significantly different from the virgin fibers, which should be taken into account in the risk assessment of fiber-containing composites.

Exposure Assessment of a High-energy Tensile Test With Large Carbon Fiber Reinforced Polymer Cables

This study investigated the particle and fiber release from two carbon fiber reinforced polymer cables that underwent high-energy tensile tests until rupture. The failing event was the source of a large amount of dust whereof a part was suspected to be containing possibly respirable fibers that could cause adverse health effects. The released fibers were suspected to migrate through small openings to the experiment control room and also to an adjacent machine hall where workers were active. To investigate the fiber release and exposure risk of the affected workers, the generated particles were measured with aerosol devices to obtain the particle size and particle concentrations. Furthermore, particles were collected on filter samples to investigate the particle shape and the fiber concentration. Three situations were monitored for the control room and the machine hall: the background concentrations, the impact of the cable failure, and the venting of the exposed rooms afterward. The results showed four important findings: The cable failure caused the release of respirable fibers with diameters below 3 μm and an average length of 13.9 μm; the released particles did migrate to the control room and to the machine hall; the measured peak fiber concentration of 0.76 fibers/cm(3) and the overall fiber concentration of 0.07 fibers/cm(3) in the control room were below the Permissible Exposure Limit (PEL) for fibers without indication of carcinogenicity; and the venting of the rooms was fast and effective. Even though respirable fibers were released, the low fiber concentration and effective venting indicated that the suspected health risks from the experiment on the affected workers was low. However, the effect of long-term exposure is not known therefore additional control measures are recommended.

Pulmonary fibrosis in response to environmental cues and molecular targets involved in its pathogenesis

Chronic lung injury resulting from a variety of different causes is frequently associated with the develop ment of pulmonary fibrosis in humans. Although the etiology of pulmonary fibrosis is generally unknown, several sources of evidence support the hypothesis that a number of environmental and occupational agents play an etiologic role in the pathogenesis of this disease. The agents discussed in this review include beryllium, nylon flock, textile printing aerosols, polyvinyl chloride and didecyldimethylammonium chloride. The authors also describe a variety of animal models, including genetically modified mice, in order to investigate the molecular mechanism of pulmonary fibrosis, focusing on chemokine receptors, regulatory T cells and transforming growth factor-β and bone morphogenetic protein signaling. Overall, we propose the concept of toxicological pulmonary fibrosis as a lung disease induced in response to environmental cues.

In vitro cytotoxicity and transforming potential of industrial carbon dust (fibers and particles) in syrian hamster embryo (SHE) cells

Carbon fibers have many applications, mainly in high-tech industries such as the aviation industry. Eleven carbon samples (fibers and particles) coming from an aeronautic group were tested for their cytotoxicity and carcinogenic potential using in vitro short-term assays in Syrian hamster embryo cells. These samples were taken during each important step of the process, i.e. from the initial heating of polyacrylonitrile fibers to pure carbon fibers. They were compared to an asbestos fiber, an amorphous silica, and two commercial graphite powders. Their physical-chemical characteristics and their capacity to release reactive oxygen species (ROS) were determined. This study showed that none of the carbon samples was able to generate ROS as measured by Electron Paramagnetic Resonance analysis, and in our biological assays, they demonstrated no morphological transformation potential and low cytotoxicity compared to positive control (chrysotile asbestos).

Pulmonary Toxicity Screening Studies in Male Rats with M5 Respirable Fibers and Particulates

M5 fiber is a high-strength, high-performance organic fiber type that is a rigid rod material and composed of heterocyclic polymer fibers of type PIPD. The aim of this study was to evaluate the acute lung toxicity of intratracheally instilled M5 respirable fibers and particulates in rats. Using a pulmonary bioassay and bridging methodology, the acute lung toxicity of intratracheally instilled M5 particulates and that of its fibers were compared with a positive control particle type, quartz, as well as a negative control particle type, carbonyl iron particles. Moreover, the results of these instillation studies were bridged with data previously generated from inhalation studies with quartz and carbonyl iron particles, using the quartz and iron particles as the inhalation/instillation bridge material. For the bioassay experimental design, in the bronchoalveolar lavage studies, the lungs of rats were intratracheally instilled with 0.5 or 0.75 mg/kg of M5 particulate or 1 or 5 mg/kg of the following control or particle types: (1) M5 long fiber preparation, (2) silica-quartz particles, and (3) carbonyl iron particles. Phosphate-buffered saline (PBS)-instilled rats served as additional controls. Following exposures, the lungs of PBS and particle-exposed rats were assessed using bronchoalveolar lavage (BAL) fluid biomarkers, cell proliferation methods, and histopathological evaluation of lung tissue at 24 h, 1 wk, 1 mo and 3 mo post instillation exposure. The bronchoalveolar lavage results demonstrated that lung exposures to quartz particles, at both concentrations but particularly at the higher dose, produced significant increases vs. controls in pulmonary inflammation and cytotoxicity indices. Exposures to M5 particulate and M5 long fiber preparation produced transient inflammatory and cell injury effects at 24 h postexposure (pe) as well as at 24 h and 1 wk pe, respectively, but these effects were not sustained when compared to quartz-silica effects. Exposures to carbonyl iron particles and PBS resulted in only minor short-term and reversible lung inflammation, likely related to the effects of the instillation procedure. Histopathological analyses of lung tissues revealed that pulmonary exposures to M5 particulate and in particular, the M5 long fiber preparation in rats produced some inflammatory responses, observed up to 1 wk postexposure. These responses were often associated with the presence of M5 long fiber in the airways or in the proximal alveolar regions but appeared to be reversible at 1 and 3 mo postexposure. In contrast, pulmonary exposures to silica-quartz particles in rats produced a dose-dependent lung inflammatory response characterized by neutrophils and foamy (lipid-containing) alveolar macrophage accumulation and evidence of early lung tissue thickening consistent with the development of pulmonary fibrosis. Based on our results, we conclude the following: (1) It was very difficult to produce M5 fibers into a respirable fibrous form; these findings suggest that aerosol exposure concentrations of respirable fibrous M5 in the workplace are likely to be rather low. (2) The particulate and long fiber preparations of M5 that were tested produced a moderate amount of pulmonary inflammatory activity, more active than our negative control, carbonyl iron particles, but substantially less active in terms of inflammation, cytotoxicity, and fibrogenic effects than the positive control particle type, silica-quartz particles. Thus, based on the results of this study, we would expect that inhaled M5 respirable fibers have a low risk potential for producing adverse pulmonary effects.

New approach to environmental tobacco smoke exposure and its relation to reemission processes

Indoor air quality is one of the factors that determine human well-being and health. Being aware of this fact, it is essential to identify the origin, kind, mechanism, and effects of harmful substances contained in the air. The issue concerning the contents and primary emission of these substances from building materials and interior furnishings is well known. Adverse effects of environmental tobacco smoke (ETS), including exposure of passive smokers, are also very well documented. To the contrary, reports on secondary and indirect emissions, especially those focused on mechanisms by which pollution is "transferred" by materials used in interior furnishings are very rare. Textiles are used in a great variety of ways as functional and decorative materials. These materials in general, and textile floor coverings in particular, are extensively utilized in fitting apartments, public buildings, and transport means. Studies on this aspect of the role played by textile materials in ETS exposure have been only fragmentary documented.

Occupational exposure to carbon/coke fibers in plants that produce green or calcined petroleum coke and potential health effects: 1. Fiber characteristics

Carbon/coke fibers are found in bulk samples of calcined petroleum coke. Carbon/coke and other fibers, including calcium silicate, cellulose, gypsum, and iron silicate, have been found in exposure monitoring of workers who make or handle green or calcined petroleum coke. Carbon/coke fibers are not classified or regulated as carcinogens by any agency, and the available literature (summarized in this article) has not reported significant adverse health effects associated with exposure to these fibers or dusts containing these fibers. However, available epidemiological and toxicological studies have limitations that prevent a definitive assessment of carbon/coke fiber toxicity. Therefore, it is prudent to monitor and control workplace concentrations. Analyses by transmission electron microscopy (TEM) indicate that the carbon/coke fibers are amorphous, irregularly shaped, and generally rather short (94% less than 20 microm long). Nearly all carbon/ coke fibers satisfying NIOSH 7400 B counting criteria are detectable by phase-contrast optical microscopy (PCOM), which permits the use of a highly efficient sequential sampling strategy for analysis. Data are presented on the distribution of carbon/coke structure and fiber lengths and diameters. Bootstrap resampling results are presented to determine confidence intervals for structure/fiber length and diameter. Data on time-weighted average concentrations are given in a companion article, but nearly all time-weighted average carbon/coke fiber concentrations were beneath 0.1 fibers per milliliter.

Biodegradability of Para-aramid Respirable-Sized Fiber-Shaped Particulates (RFP) in Human Lung Cells1

Using both in vivo (inhalation) and in vitro (cell culture) studies, we previously reported that p-aramid respirable fibers (RFP--defined as respirable-sized fiber-shaped particulates) are biodegraded in lungs and lung cells of rats following exposures. The current studies were undertaken to determine whether shortening mechanisms of p-aramid RFP biodegradability are also operative in human lung cells. Cultures of human A549 lung epithelial cells (A549), primary alveolar macrophages (HBAL) (collected via bronchoalveolar lavage [BAL]) from volunteers), and co-cultures (Co) of the A549 and HBAL were incubated with p-aramid RFP for either 1 h, 1 day, or 1 week to assess RFP shortening. Lengths of RFP were measured using scanning electron microscopy (SEM) following fixation, digestion of culture tissue components, and processing. Similar to findings using rat lung cells, only slight RFP shortening was measured in A549 cultures at 1-day and 1-week post-incubation. More importantly, in HBAL and Co groups, greater transverse cleavage of p-aramid RFP was measured at 1-day and 1-week postexposure compared to 1-h HBAL or Co groups, or in any A549 groups. In contrast, cellulose RFP, a biopersistent reference control fiber, were not measurably shortened under similar circumstances. Second, p-aramid RFP were incubated either with phosphate-buffered saline (PBS), or acellular BAL fluids from human volunteers or rats and processed for SEM analysis of RFP lengths. Mean lengths of p-aramid RFP incubated with human or rat BAL fluids were substantially decreased compared to PBS. Similar to our findings with rat lung cells, components of human lung fluids coat the p-aramid RFP as a prerequisite for subsequent enzymatic cleavage by human phagocytic lung cells and this finding reinforces the concept that inhaled p-aramid RFP are likely to be biodegradable in the lungs of humans.

Nanoparticles - known and unknown health risks

Manmade nanoparticles range from the well-established multi-ton production of carbon black and fumed silica for applications in plastic fillers and car tyres to microgram quantities of fluorescent quantum dots used as markers in biological imaging. As nano-sciences are experiencing massive investment worldwide, there will be a further rise in consumer products relying on nanotechnology. While benefits of nanotechnology are widely publicised, the discussion of the potential effects of their widespread use in the consumer and industrial products are just beginning to emerge. This review provides comprehensive analysis of data available on health effects of nanomaterials.

Four-week inhalation toxicity study in rats with nylon respirable fibers: rapid lung clearance

This inhalation toxicity study in rats was conducted to assess the hazard potential for workers inhaling Nylon respirable fibers. Groups of 48 male rats each were exposed, nose-only, 6h per day, 5 days per week, for 4 weeks to aerosols of uncoated, finish-free Nylon respirable-sized, fiber-shaped particulates (RFP) at concentrations of 0, 4, 15 and 57 fibers (f)/cm3. Nylon RFPs were prepared using flock rotary cutters followed by vigorous opening procedures. After exposures, the lungs of sham and Nylon-exposed rats were assessed at 1 and 8 days, and 1, 3, 6 and 12 months postexposure. The results showed that the retained mean lung burdens at 1 day postexposure were 1.75E+07 RFP/lung (high level). Mean lengths and diameters of the Nylon aerosol were 9.8 and 1.6 microm, respectively. Lung clearance of Nylon RFPs was rapid over the 12-month period. There were no significant increases in lung weights, indications of pulmonary inflammation, or alveolar macrophage functional deficits in Nylon-exposed animals versus controls based on cell differentials, bronchoalveolar lavage (BAL) fluid analyses, and macrophage phagocytosis or chemotaxis activity. Histopathology revealed no adverse lower pulmonary or upper respiratory effects. In summary, the no-observed-effect level (NOEL) for inhaled Nylon RFP was 57f/cm3 (20mg/m3), the highest concentration tested.

Biodegradability of inhaled p-aramid respirable fiber-shaped particulates (RFP): mechanisms of RFP shortening and evidence of reversibility of pulmonary lesions

These studies elucidated mechanisms of inhaled p-aramid respirable fiber-shaped particulates (RFP) biodegradation in the lungs of exposed rats and hamsters. We postulate that lung fluids coat/activate inhaled p-aramid RFP which deposits in the lung and promote enzymatic attack and consequent shortening. p-Aramid or cellulose (biopersistent control) RFP were instilled into the lungs of rats and the lungs digested 24 h later using two different (KOH or enzymatic) digestion techniques. In vivo, the enzyme but not the KOH solution produced shortening of p-aramid but not cellulose RFP recovered from the lungs. For in vitro studies, the two RFP-types were incubated with BAL fluids and underwent simulated digestions; also rat lung epithelial cells, macrophages or co-cultures were incubated with p-aramid and digested at 1, 24, or 168 h postexposure. The results of in vitro acellular studies demonstrated that only p-aramid RFP incubated in BAL fluids and digested by the enzyme method were shortened. In vitro cellular studies demonstrated a shortening of p-aramid RFP in macrophages and co-cultures but not in lung epithelial cells at 24 h and 1 week postexposure. These results demonstrate that lung fluids coat and catalyze the p-aramid RFP as a prelude for shortening and describe a likely mechanism for the biodegradability of inhaled p-aramid RFP in the lungs of exposed animals.