[Risk management of Hexavalent Chromium released through fettling operations in the manufacturing of aircraft wings]

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Acknowledgement

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Abstract

Due to its wide industrial use, chromium is considered a serious environmental pollutant. Contamination of soil and water by chromium (Cr) is of recent concern. Toxicity of Cr to plants depends on its valence state: Cr (VI) is highly toxic and mobile whereas Cr (III) is less toxic. Since plants lack a specific transport system for Cr, it is taken up by carriers of essential ions such as sulphate or iron. Toxic effects of Cr on plant growth and development include alterations in the germination process as well as in the growth of roots, stems and leaves, which may affect total dry matter production and yield. Cr also causes deleterious effects on plant physiological processes such as photosynthesis, water relations and mineral nutrition. Metabolic alterations by Cr exposure have also been described in plants either by a direct effect on enzymes or other metabolites or by its ability to generate reactive oxygen species which may cause oxidative stress.

Table of Contents

CHAPTER 1: INTRODUCTION6

Background7

CHAPTER 2: LITERATURE REVIEW8

Chromium Air Emissions8

Hexavalent Chromium13

Uses and Toxicity15

Cr (VI) Regulations17

CHAPTER 3: METHODOLOGY19

Research Design19

An understanding of Chromium (Cr)20

Atmospheric Dispersion Modelling24

CHAPTER 4: FINDINGS29

Hexavalent Chromium (Cr6)29

Potassium Dichromate30

What Happens to Chromium in the Body?31

Dermal (Skin)32

Biological Adverse Health Effects of Hexavalent Chromium (Cr6)32

Inhalation32

Examples of Occupational Diseases35

Health effects of chromium39

Environmental effects of chromium40

Legislation and Exposure Limits42

Chromates: Exposure Limits and Control Measures43

Fettling operations44

Example46

What is the Anodising process of aluminium aircraft components?48

Airbus UK - (Approval No. 10064)51

Anodizing Operating Parameters52

Hexavalent chromium primer paints54

CHAPTER 5: DISCUSSION AND ANALYSIS55

Environmental Hazards55

CHAPTER 6: CONCLUSION58

REFERENCES63

Chapter 1: Introduction

Hexavalent Chromium (Cr6), is widely used in the production and manufacturing of aircraft. The elements to which aircraft are exposed far exceed those of normal modes of transport, and for this reason it is required that the working parts of the aircraft are given the maximum defences against corrosion. It has been accepted for over 40 years that the most beneficial process to help combat such materials against corrosion is through the anodising of the metals/alloys with Chromic acid. Primer coatings of chromium-based paints are applied for extra protection, and with the operations carried out within the workplace it can mean vast amounts of exposure to those in the vicinity of such operations.

A further or secondary attribute of the chromic acid anodising process, is the ability or versatility of Cr6 to enable Non Destructive Testing (NDT) to be carried out. This process is to detect flaws or imperfections in the materials and Cr6 allows the detection of such abnormalities without affecting or damaging ...