Each year vast amounts of plastic are produced worldwide. When released to the environment, plastics accumulate, and plastic debris in the world's oceans is of particular environmental concern. More than 60% of all floating debris in the oceans is plastic and amounts are increasing each year. Plastic polymers in the marine environment are exposed to sunlight, oxidants and physical stress, and over time they weather and degrade. The degradation processes and products must be understood to detect and evaluate potential environmental hazards. Some attention has been drawn to additives and persistent organic pollutants that sorb to the plastic surface, but so far the chemicals generated by degradation of the plastic polymers themselves have not been well studied from an environmental perspective. In this paper we review available information about the degradation pathways and chemicals that are formed by degradation of the six plastic types that are most widely used in Europe. We extrapolate that information to likely pathways and possible degradation products under environmental conditions found on the oceans' surface. The potential degradation pathways and products depend on the polymer type. UV-radiation and oxygen are the most important factors that initiate degradation of polymers with a carbon-carbon backbone, leading to chain scission. Smaller polymer fragments formed by chain scission are more susceptible to biodegradation and therefore abiotic degradation is expected to precede biodegradation. When heteroatoms are present in the main chain of a polymer, degradation proceeds by photo-oxidation, hydrolysis, and biodegradation. Degradation of plastic polymers can lead to low molecular weight polymer fragments, like monomers and oligomers, and formation of new end groups, especially carboxylic acids.

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Pathways for degradation of plastic polymers floating in the marine environment

This review is an attempt to present and describe the major immediate toxic threats in fire situations. These are carbon monoxide, a multitude of irritating organic chemicals in the smoke, oxygen depletion, and heat. During the past 50 years, synthetic polymers have been introduced in buildings in very large quantities. Many contain nitrogen or halogens, resulting in the release of hydrogen cyanide and inorganic acids in fire smoke as additional toxic threats. An analysis of toxicological findings in fire and nonfire deaths and the results of animal exposures to smoke from a variety of burning materials indicate that carbon monoxide is still likely to be the major toxicant in modern fires. However, the additional toxic threats mentioned above can sometimes be the principal cause of death or their addition can result in much lower than expected carboxyhemoglobin levels in fire victims. This analysis also revealed that hydrogen cyanide is likely to be present in appreciable amounts in the blood of fire victims in modern fires. The mechanisms of action of acute carbon monoxide and hydrogen cyanide poisonings are reviewed, with cases presented to illustrate how each chemical can be a major contributor or how they may interact. Also, lethal levels of carboxyhemoglobin and cyanide in blood are suggested from an analysis of the results of a large number of fire victims from different fire scenarios. The contribution of oxygen depletion and heat stress are more difficult to establish. From the analysis of several fire scenarios, they may play a major role in the room of origin at the beginning of a fire. The results in animal studies indicate that when major oxygen depletion (<10%) is added to lethal or sublethal levels of carbon monoxide or hydrogen cyanide its major role is to substantially reduce the time to death. In these experiments the carboxyhemoglobin level at death was slightly reduced from the expected level with exposure to carbon monoxide alone. However, blood cyanide was reduced by a factor of ten from the expected level with exposure to hydrogen cyanide alone. This is another factor (among many other presented) complicating the task of establishing the contribution of cyanide in the death of fire victims, from its analysis in their blood. Finally the role of ethanol intoxication, as it may influence carboxyhemoglobin levels at death, is reviewed. Its role is minor, if any, but the data available on ethanol in brain tissue and blood of fire victims confirmed that brain ethanol level is an excellent predictor of blood ethanol.

Toxicity of fire smoke.

Carbon monoxide poisoning is the leading cause of poisoning deaths in the US, and published reports of carbon monoxide related morbidity and mortality can vary widely. Common morbidity involves myocardial and/or neurologic injury including delayed neurologic sequelae. The pathophysiology of this entity is complex, involving hypoxic stress on the basis of interference with oxygen transport to the cells and possibly impairing electron transport. Carbon monoxide can also affect leukocytes, platelets and the endothelium, inducing a cascade of effects resulting in oxidative injury. Carboxyhemoglobin levels are valuable for confirming carbon monoxide exposure but cannot be used to stratify severity of poisoning, predict prognosis, or indicate a specific treatment plan. Oxygen therapy is the key treatment of carbon monoxide intoxication, and hyperbaric oxygen has been shown to interdict and improve clinical outcome in some patients. Immediate treatment with a high fraction of inspired oxygen and careful clinical evaluation are mandatory. Timely referral for hyperbaric oxygen is indicated for patients with any history of unconsciousness, cardiovascular instability or ischemia, and persistent mental and/or neurologic deficits. Hyperbaric oxygen should also be considered in certain other patient subsets.

Pathophysiology and Treatment of Carbon Monoxide Poisoning

Polystyrene nanoparticles: Sources, occurrence in the environment, distribution in tissues, accumulation and toxicity to various organisms.

Nanoparticles of various shapes, sizes, and materials carrying different surface modifications have numerous technological and biomedical applications. Yet, the mechanisms by which nanoparticles interact with biological structures as well as their biological impact and hazards remain poorly investigated. Due to their large surface to volume ratio, nanoparticles usually exhibit properties that differ from those of bulk materials. Particularly, the surface chemistry of the nanoparticles is crucial for their durability and solubility in biological media as well as for their biocompatibility and biodistribution. Polystyrene does not degrade in the cellular environment and exhibits no short-term cytotoxicity. Because polystyrene nanoparticles can be easily synthesized in a wide range of sizes with distinct surface functionalizations, they are perfectly suited as model particles to study the effects of the particle surface characteristics on various biological parameters. Therefore, we have exploited polystyrene nanoparticles as a convenient platform to study bio–nano interactions. This review summarizes studies on positively and negatively charged polystyrene nanoparticles and compares them with clinically used superparamagnetic iron oxide nanoparticles.

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Functionalized polystyrene nanoparticles as a platform for studying bio–nano interactions

Effects of exposure to single or multiple combinations of the predominant toxic gases and low oxygen atmospheres produced in fires

The current English literature through 1984 on the products of pyrolysis and combustion from polystyrenes and the toxicity of those products is reviewed. Among 57 compounds detected by chemical analyses of the thermal decomposition products produced under various atmospheric conditions (vacuum, inert and oxidative), the main volatile component is the styrene monomer, Evidence is provided that the mass fraction of styrene increases with furnace temperatures at least through 500°C. At 800°C and above, the concentration of styrene decreases. In oxidative atmospheres, carbon monoxide (CO), carbon dioxide (CO2) and oxidative hydrocarbons are formed. The concentrations of CO and CO2 are a function of temperature and combustion conditions, i.e. greater amounts are produced in the flaming than in the non-flaming mode. Eleven different test procedures were used to evaluate the toxicity of the pyrolysis and combustion atmospheres of polystyrenes. The more toxic environments produced under flaming conditions appear to be mainly attributed to CO and CO2 but rather to some other toxicant, probably the styrene monomer. When compared with other common materials used in buildings and residences, polystyrenes, in general, are among the least toxic.

Polystyrenes -- A Review of the Literature on the Products of Thermal Decomposition and Toxicity

Toxicological interactions between carbon monoxide and carbon dioxide

The toxicity of the thermal-decomposition products from two flexible polyurethane foams (with and without a fire retardant) and a cotton upholstery fabric was evaluated by a series of small-scale and large-scale tests single mock-up upholstery chair tests during smoldering or flaming decomposition. In addition other fire property data such as rates of heat release, effective heats of combustion, specific gas species yields, and smoke obscuration were measured. The degree of toxicity observed during and following the flaming tests (both large-scale room burns and the NBS Toxicity Tests) could be explained by a 3-Gas Model which includes the combined toxicological effects of CO, CO/sub 2/, and HCN. Essentially, no animal deaths were noted during the thirty minute exposures to the non-flaming or smoldering combustion products produced in the NBS Toxicity Test Method or the large-scale room test. In the large-scale room tests, little toxicological difference was noted between decomposition products from the burn room and a second room 12 meters away.

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Fire toxicity scaling

Ten large-scale single-compartment fire tests were performed using two polyurethane foams and a cotton upholstery fabric. Animals were exposed to the products of decomposition of cushion assemblies burned under three different combustion modes: smoldering combustion; flaming combustion; and smoldering-to-flaming transition combustion. Comparison of gas yields (CO, CO/sub 2/, and HCN) between these tests and prior large- and small-scale tests showed that the CO and CO/sub 2/ yields agreed within a factor of 3, while the NBS Toxicity Protocol produced 10 times more HCN in the flaming mode and ramped heating mode than the large-scale tests. Model calculations showed that within-exposure animal deaths in small- and large-scale tests correlated with model values greater than 0.7. Burn room animal deaths could not be explained in terms of the four gases used in the N-gas model.

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Joshua L. Gurman

Papers

Effects of exposure to single or multiple combinations of the predominant toxic gases and low oxygen atmospheres produced in fires

Polystyrenes -- A Review of the Literature on the Products of Thermal Decomposition and Toxicity

Toxicological interactions between carbon monoxide and carbon dioxide

Fire toxicity scaling

Large-scale compartment-fire toxicity study: comparison with small-scale toxicity test results