Dioxin and human health Essay Example | Topics and Well Written Essays - 500 words

Dioxin and human health - Essay Example The producibility is relatively high in presence of a catalyst like iron. Chemistry of Dioxins Para-dibenzodioxins are formed when two oxygens combines two benzenes (or chlorinated benzenes). The number of isomers is several as both could have upto 8 chlorines – 75 for PCCDs and 135 for PCDFs. These compounds are called as congeners. Toxicity is expressed as Toxic Equivalent Factor (TEF) and toxicity is based on 2,3,7,8 TCCD which is expressed as TEF. The toxicity is caused because of the four chlorine atoms at positions 2, 3, 7, 8 on the dioxin molecules. The toxicity is expressed as pg TEQ/g lipid (ppt) and is summed up based upon their toxicity equivalent concentrations. OCCD is the most abundant isomer related to human contamination followed by the 2,3,7,8 substituted hepta and hexa-chloro congeners. 2,3,7,8 TCCD is normally less abundant than PCCD. The activation of Ah receptor determines the TEF. The oxygen bond between the two benzenes could be substituted to sulphur or azide. Chlorine could be replaced by bromine. Effect of Dioxins on Human Health Eating, breathing, and polluted air and skin contact with contaminated soil and materials are the major routes for human exposure. The PCCDs reach the blood stream after passing from the gastrointestinal tract and eating food containing the PCCDs.

(Q2.The Government states that 'the adoption of the NEC3 2005 Essay

(Q2.The Government states that 'the adoption of the NEC3 2005 Engineering and Construction contract suits the needs of a modern construction industry'. Provide an appraisal in response to such a statement - Essay Example It is also been used in countries around the world like South Africa. Its use implies that it suits the requirements of the modern construction and engineering industry. However, opponents beg to differ (Gould, 2007). The Government Commerce in the United Kingdom has validated NEC3 for utilisation in the construction projects that are funded by the public. NEC3 also meets the requirements of the Achieving Excellence in Construction (Rowlinson, 2011). In the validation by the office of the Government Commerce, it is noted that NEC3 satisfies the principles set out by AEC, whose aim is to boost performance in the construction industry. It is also noted NEC3 is an up to date group of contracts that enhances the enactment of the right principles in construction projects. NEC3 is made up of three main elements. These key elements are the risk management, the settings of the contract, and the management of the project. Thus, under the three components, NEC3 looks at the type of regulations, the compensation, what and when of the project, and identifies people in charge of the project like the supervisor and the contractor (Construction Industry Development Board, 2005). In spite of the opposition from different sectors, an evaluation of the facts surrounding NEC3 can determine if it suits the requirements of the modern construction industry. NEC3 is composed of a group of two clauses, optional and key. Just to name but a few, the key clauses include time, general, payment, title, and compensation; while the optional ones include options A to F, which is the management contract. The beneficial aspects associated with NEC3 include fruitful approval by contractors and customers. It is not rigid in terms of the designs; hence, permitting any form of association between the contractors and the employers. It is characterised by brevity and simplicity in