Department of Medical History

The history of pulp and paper bleaching: respiratory-health effects

Inhalation of chlorine gas, with subsequent hydrolysis in the airway and lungs to form hydrochloric acid (HCl) and hypochlorous acid (HOCl), can cause pulmonary edema (i.e., fluid build-up in the lungs), pulmonary inflammation (with or without infection), respiratory failure, and death. The HOCl produced from chlorine is known to react with tyrosine to form adducts via electrophilic aromatic substitution, resulting in 3-chlorotyrosine and 3,5-dichlorotyrosine adducts. While several analysis methods are available for determining these adducts, each method has significant disadvantages. Hence, a simple and sensitive ultra-high performance liquid chromatography-tandem mass spectroscopy (UHPLC-MS/MS) method was developed for the determination of chlorotyrosine adducts. The sample preparation involves base hydrolysis of isolated plasma proteins to form 2-chlorophenol (CP) from monochlorotyrosine adducts and 2,6-dichlorophenol (2,6-DCP), from dichlorotyrosine adducts, as markers of chlorine exposure. The chlorophenols are extracted with cyclohexane prior to UHPLC-MS/MS analysis. The method produced excellent sensitivity for 2,6-DCP with a limit of detection of 2.2 μg/kg, calibration curve linearity extending from 0.054–54 mg/kg (R² ≥ 0.9997 and %RA > 94), and accuracy and precision of 100 ± 14 %, and <15 % relative standard deviation, respectively. The sensitivity of the method for 2-CP was relatively poor, so it was used only as a secondary marker for severe chlorine exposure. The method successfully detected elevated levels of 2,6-DCP from hypochlorite-spiked plasma protein and plasma protein isolated from chlorine-exposed rats.

Bleaching is one of the important stages in paper manufacturing to make the end paper product brighter and whiter. Over the years, there have been various technologies developed to ensure that the processes employed do not pose negative impact on the environment. This chapter describes basic understanding of bleaching technology mainly for chemical, mechanical, and recovered pulps as well as for other materials.

Chlorine dioxide (ClO₂) bleaching wastewater from bagasse brings a threat to human health. The intimate coupling of photocatalysis and biodegradation (ICPB) as a prospective green technique can remove environmental pollutants. Therefore, this study innovatively integrates functional bacteria with the ICPB system (ICPFB) and discusses the degradation mechanism, pathway, kinetic model, and microbial response behavior of the system to wastewater. The results show that the ICPFB system can simultaneously remove 95% absorbable organic halogen (AOX), 91% COD and 85% dissolved organic carbon (DOC), outperforming single photocatalysis (AOX 72%, COD 80%, DOC 68%) and biodegradation (AOX 41.4%, COD 66%, DOC 45%). Meanwhile, the reaction kinetics model of the ICPFB system is dC/dt = -KC^1.22. According to the GC-MS analysis of degradation products, the degradation of organic compounds in wastewater involves gradual dechlorination and aromatic ring opening. Lastly, the Biofilm analysis shows that the functional bacteria possess abilities of dechlorination, aromatic ring opening and carbon oxidation.

“Adsorbable organic halogens (AOX)” is a comprehensive index defined as the sum of all halogenated organic compounds which can be adsorbed onto the activated carbon and detected by microcoulometry. AOX have received increasing attention because of their widespread distribution, potential toxicity and bioaccumulation. It is urgent to control AOX pollution due to their hazard to eco-environment and human health. However, a significant gap still exists in our knowledge of the source, pollution extent and character of AOX. This review describes the contamination status of AOX and identifies their key sources, pollution-intensive sectors as well as emission hotspots. Considering the generation of AOX during high salinity wastewater treatments and the accumulation of AOX in sludges, the wastewater treatment plants (WWTPs), which have been neglected previously, are identified as potential sources of AOX. Besides, the performance and innovative improvements of AOX removal technologies are critically evaluated. Different scenarios are proposed to enhance removal efficiency and avoid byproduct generation during AOX treatment processes.

This chapter covers the history of toxicology from ancient times to the present. The origins of toxicology derived from the exploration of ancient peoples’ interaction with their environment and concentrated on what is a poison and what is not a poison. The uses of toxicology are covered through history with numerous episodes as examples. The chapter updates the current day emphasis on the involvement of toxicology with the ever-increasing volume of new chemicals being introduced to the public. There is an emphasis on toxicity and the various techniques used in toxicity testing, such as computational processes, are presented. Ecotoxicology is presented to emphasize the need to understand the environment we live in and interact with relative to new, and some old, chemicals being introduced.

Chlorine gas is used widely by industry and as a disinfectant and bleach, and, due to its toxicity and ease of procurement, has been used as a chemical warfare agent. Chlorine is a strong oxidizer that hydrolyzes in water to form hydrochloric and hypochlorous acid. Upon chlorine inhalation, the respiratory tract is the predominant target organ in humans and animals as chlorine is a contact irritant. Exposure causes sensory irritation and pulmonary dysfunction, and at sufficiently high concentrations results in lung lesions and injury to other internal organs including the heart. Human and animal studies have shown that chlorine toxicity is influenced more by exposure concentration than duration, is gender-independent, and increases with age, cigarette smoking, and preexisting respiratory conditions such as asthma and airway hyperreactivity. Treatment is largely supportive, although animal studies are examining the utility of various compounds for chlorine-specific treatment based on its mechanism of action.