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Essay: Priority Existing Chemical (PEC) Report of Hexabromocyclododecane (HBCD)

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Priority Existing Chemical (PEC) Report of Hexabromocyclododecane (HBCD) [PEC/34, 2012], carried out under the National Industrial Chemicals Notification and Assessment Scheme (NICNAS)

As HBCD has been determined to be a hazardous substance in relation to human health according to the Safe Work Australia’s Approved criteria for classification of hazardous

SCOPE

This analytical summary and briefing note will provide the Executive Director/Chief Executive an overview of the occupational risk assessment done by the NICNAS, particularly the 2012 PEC Report of HBCD by the NICNAS. This is to allow the Director to answer any questions regarding the report with the necessary information in hand.

Introduction

Context and Background

In 2001 a preliminary PEC assessment for HBCD was piloted by NICNAS over the concern of widespread use of flame retardants such as HBCD in industrial situations. A report of occupational exposure among other environments was published and a future full risk assessment was recommended.

Issue Identification

HBCD, an additive polybrominated flame retardant (PBRS), is not manufactured in Australia and is generally imported into Australia as liquid polystyrene resins (EPS) that are components of plastic inside finished articles. Examples of finished articles containing HBCD components are extruded polystyrene (XPS) boards, office equipment such as inkjet printers or scanners, and insulation and ventilation units for offices. Imports of HBCD have sharply declined as of since 2010 (NICNAS, 2012). HBCD’s widepsread existence in household and occupational environments, along with concerns of toxicity and environmental persistence (United Nations, 2013), has caused concerns and led to its declaration as a Priority Existing Chemical (PEC) by the Commonwealth Chemical Gazette in 2005. This has also called for a full risk assessment report, which is the basis of this analytical summary used to answer questions from the Board of Directors regarding occupational health hazards and exposure of HBCDs.

HAZARD ASSESSMENT

As HBCD is the primary hazard for any occupational health risks in this report, the relevant hazard assessment will be on human health hazard parameters. Parameters are grouped into: Toxicokinetics and Metabolism (Absorption, Distribution, Metabolism, and Elimination/Excretion); Effects of laboratory mammals (Various toxicities, skin and eye irritation, Sensitisation); and other Human health effects. The study results for hazard assessments are primarily based on animal experiments, with very limited data for human studies. Any statistically significant parameters classed as a hazard received a no adverse effect level (NOAEL) score to show the maximum known level without adverse effect.

Results from Report

Rat studies show that HBCD is rapidly absorbed with a half-life of 2 hours. HBCD is also widely distributed throughout the body and is excreted rapidly with radiolabelled HBCD primarily excreted in faeces.

Acute Toxicity in oral, dermal and inhalation routes is low, and HBCD does not irritate skin or eyes in animals. In both animals and humans, HBCD does not sensitise the skin, and there is no data on respiratory sensitisation. Studies in Repeated dose toxicity consistently showed dose-dependent increases in liver weights, with the highest increase in liver weight showed after 90 days by 48% and considered an adverse effect, despite histopathological changes being minimal until the 90-day dose. Other increases were reported including thyroid pituitary effects. As a result of the dose dependent liver weight increase, HBCD was given a NOAEL of 10mg/kg bodyweight.

HBCD did not display carcinogenic nor genotoxic properties in long term mice studies. There were also no signs of significant reproductive toxicity, except for reduced primordial follicles in a two-generation rat study. As a result, a NOAEL score of 10.2mg/kg bodyweight was considered for reproductive toxicity.

Developmental effects showed more significant results in two studies conducted, with organs such as infant bodyweight, time to vaginal opening, testes weight, and decreased vital organ weight and bone mineral density decrease showing statistically significant results. A dose dependent increase in mortality during lactation was also seen, along with results in late eye opening on postnatal days and shorter basic reflexes, indicating late development. Developmental neurotoxicity was also indicated in these studies (NICNAS, 2012).

OCCUPATIONAL EXPOSURE ASSESSMENT

The health risks in HBCD exposure is depends on the form of HBCD used and the nature of work in relation to HBCD. Exposure to workers handling HBCD was determined by exposures during importation and packaging across multiple industries including the polymer industry. The routes of administration studied for exposure were oral, inhalation and dermal routes. The median and 90th percentile values were used to represent typical and reasonable worst-case estimates, respectively.

HBCD in the form of powder or granular formulations were estimated to have low risk of adverse health risk via inhalation, except in the event of an accident. There is also a low risk of acute adverse health effects such as inhalation toxicity, skin, eye and respiratory irritation. High risk was reported for workers in the polymer industry exposed during HBCD compounding, conversion or moulding activities. HBCD workers who weighed the substance also were of high risk of health effects. Regarding these high risk scenarios in a realistic worst-case setting, high risk is indicated for both powder and granular forms (NICNAS, 2012).

DISCUSSION

For Hazard Assessment parameters, HBCD is known to be persistent, and thus the NOAEL values in these studies can be accepted to be used for the general human population and occupational use situations. Through animal studies HBCD showed adverse effects in repeat-dose and developmental toxicity studies

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