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Environmental chemistry and toxicology:

Principles and practices

Barry N Noller Wednesday 29 January 2014

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It is important to understand the principles of toxicology and practices of disciplines that combine in the risk assessment process to enable using Environmental Chemistry and Toxicology for understanding the nature and processes of metals and metalloids in environmental systems and their effects on biota..

OUTLINE OF TALK

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Significance of metals and metalloids

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1. Heavy metals and metalloids are toxic substances to humans and the environment and usually their effects are well defined by guidelines for soil and sediment using risk based approaches

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2. The common heavy metals are chromium, cobalt, copper , cadmium, lead , manganese, mercury, nickel, silver, thallium, vanadium, zinc and uranium.

Antimony, arsenic and selenium are metalloids.

6SMI KT Short Course Practical Monitoring 22 - 24 March 2010, Brisbane

3. Heavy metals may arise from natural and man-made sources

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Toxicology is the science of the study of poisons.

It involves a multi-disciplinary approach to evaluation of the adverse impact of chemical compounds of both natural and anthropogenic origin, on various living systems.

Klaassen, C.D., and D.L. Eaton. 1991. Principles of toxicology. Pp. 12-49 in Casarett and Doull’s Toxicology: The Basic Science of Poisons, 4th Ed., M.O. Amdur, J. Doull, and C.D. Klaassen, eds. New York: Pergamon Press.

TOXICOLOGY

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The committee’s vision sets the stage for transformative changes in toxicity testing in the regulatory agencies and the larger scientific community. Although advances in the state of the science are indispensable to realization of the vision, corresponding institutional changes are also important. The changes will promote acceptance of the principles and methods envisioned. Acceptance will depend on several factors, some having scientific origins. For example, the new testing requirements will be expected to reflect the state of the science and to be founded on peer-reviewed research, established protocols, validated models, case examples, and other scientific features.

TOXICITY TESTING IN THE 21ST CENTURY NATIONAL RESEARCH COUNCIL, 2007

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Toxicology involves a multi-disciplinary approach to evaluation of the adverse impact of chemical compounds of both natural and anthropogenic origin, on various living systems. Sub-disciplines of toxicology include, environmental toxicology, (chronic impact from environment on humans), clinical toxicology, (acute impact on humans) and ecotoxicology, (impact on biota and ecological systems).

Risk-assessment is a key toxicological tool that enables scientific study of the effects of poisons to proceed.

TOXICOLOGY AND RISK ASSESSMENT

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Venn Diagram showing Environmental Toxicology and Ecological Toxicology

ENV.TOX

ACUTEMEDICINE

TOXICOLOGY

PUBLICHEALTH

ENVIRONMENTENV.

HEALTH

ANATOMY

BIOCHEMISTRY

CHEMISTRY

MICROBIOLOGY

MOLECULARBIOLOGY

MEDICINE

PATHOLOGY

PHARMACOLOGY

ZOOLOGY

ENV. TOX - Environmental Toxicology

ECO-TOX - Ecological Toxicology

CLIN-TOX - Clinical Toxicology

ENV. HEALTH - Environmental Health

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Since there are diverse inter-disciplinary aspects to toxicology it is better displayed in the form of a Venn diagram. This diagram describes the placement of different forms of toxicology, the disciplinary aspects applying to it and associations with it. The disciplinary blocks to the right, are some of those that underpin toxicology including chemistry and are utilised in it.

The separation of sub-disciplines of toxicology is clearly identified. Environmental toxicology as a human health topic, allies with public health and

the environment. Ecotoxicology is placed at the interface between toxicology and the environment. The link between acute medicine and toxicology identifies clinical toxicology.

Although allied to pharmacology, toxicology relates to all potential noxious agents, most having no relevance to therapeutics.

TOXICOLOGY INVOLVES MANY DISCIPLINES

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The central role of risk-assessment in toxicology is clearly identified when its particular application in regulatory toxicology is examined.

CENTRAL ROLE OF RISK ASSESSMENT

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Risk Assessment Framework

Human Health Risk Assessment

Ecological Risk Assessment

Process followed:• NEPC/NEPMs• NH&MRC• USEPA• ADWG

Process followed:Ecological / Aquatic and Agricultural / Livestock

• ANZECC

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Human health risk assessment (USEPA and enHealth 2012)

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Guideline values may be used to assess the Issue Identification step of Health Risk Assessment.However it is assumed that bioavailability of metals and metalloids is 100%

SOIL CONTAMINATION GUIDELINES

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NEPM Guideline Values –Soil (< 250 µm)

According to the NEPC risk assessment process, exceedances of HILs trigger require a Tier II risk assessment including toxicity assessment. Hence bioaccessibility is used to predict bioavailability and calculated for each site to allow for a site specific risk assessment. (Default is 100% bioavailability)

Metal (mg/kg)

Soil HIL(Level A)

Soil HIL(Level D)

Soil HIL(Level E)

Soil HIL(Level F)

Lead (Pb) 300 1200 600 1500

Level A – Standard residential with garden/accessible soilLevel D – Residential with minimal soil accessLevel E – Parks, recreational open space and playing fieldsLevel F – Commercial/Industrial

NEPM Soil Investigation Levels (HIL = Health Investigation Levels)

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NEPM Soil Investigation Levels (HIL = Health Investigation Level and EIL = Ecological Investigation levels)

Metal/ Metalloid

SoilHIL (Level A)

SoilHIL (Level D)

SoilHIL (Level E)

SoilHIL (Level F)

SoilEIL (Int Urban)

Antimony (Sb) NA NA NA NA _Arsenic (As) 100 400 200 500 20

Cadmium (Cd) 20 80 40 100 3

Cobalt (Co) 100 400 200 500 _Copper (Cu) 1,000 4,000 2,000 5,000 100Lead (Pb) 300 1200 600 1,500 600Manganese (Mn) 1,500 6,000 3,000 7,500 500

Nickel (Ni) 600 2,400 600 3,000 60Zinc (Zn) 7,000 28,000 14,000 35,000 200

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In cases of minor exceedances of investigation levels or exceedances related to contaminants which have low human toxicity and limited mobility, a qualitative risk assessment may be sufficient.

The risk assessment process (enHealth, 2012) may lead to the development of site-specific response levels generated by risk assessment and agreed in consultation between the professionals assessing the site and the regulatory authorities.

The Tier II risk assessment process described by NEPC (2013) allows for toxicity assessment when HILs for the designated category or land use is exceeded.

19SMI KT Short Course Practical Monitoring 22 - 24 March 2010, Brisbane

Bioavailability is defined as the fraction of the administered dose that reaches the systemic circulation of an organism (NRC, 2003). This is determined using animal dosing (in vivo) experiments. In the in vitro system, bioavailability of a contaminant is referred to as bioaccessibility and is an alternative quantitative indicator of in vivo derived bioavailability estimates. Bioaccessibility as a measure of bioavailability has been evaluated by the USEPA (2007).

 

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The measurement of bioavailability via animal uptake is expensive and time consuming. A more practical approach is to use the in-vitro PBET (physiologically based extraction test) (Ruby et al. 1996).

PBET measures bioaccessible metal and metalloid concentrations and is an in vitro test that simulates extraction by the gastro-intestinal (GI) tract of a human being (Ruby et al. 1996) to predict the bioavailability (BA) of a substance or its absorption via the gut.

PBET considers a range of stomach pH’s to take into consideration varying bioavailabilities resulting from differing stomach conditions (e.g. fasting).

 

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Chemical speciation of mine wastes, soils and sediments and its relationship to bioavailability in the context of health risk assessment

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Media campaign that there was an issueCamberwell NSW

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QLD Flood Enquiry 2012

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Key question is how to follow the transfer of metals or metalloids through various environmental pathways

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Contamination from Mining and Mineral processing

In mineral rich countries such as Australia, mine sites are potential source of metals and metalloids

Key Issues

– If not properly managed, dispersion of metals and metalloids may cause adverse effects on the environment and human health

– Major environmental source of metals and metalloids including arsenic, cadmium, copper, lead and zinc through their associations with base metal mineralogy

– Contamination can arise from mine processing of ores, overflow from tailings ponds, and run-off from the general mine area which can lead to extensive offsite contamination.

– Contamination of soil and water by metals and metalloids from both mining residues and tailings can result in bioaccumulation by terrestrial and aquatic biota and to human uptake

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Lead from Mining and Mineral Processing

o Significant geographical distribution (radially from the smelter) of lead in town receptor (soil, air, and blood lead level) Port Pirie, SA – BLL following the major wind direction; high risk

area is downstream of the lead smelter (Calder et al., 1994)

o Ongoing smelter emission as point source

Trail, Canada – improvement following a new smelter (5.9 µg/dL from 11.5 µg/dL); 3-month shutdown (4.7 µg/dL) (Hilts, 2003)

o Exterior soils and interior dusts

o Ingestion vs Inhalation

Birmingham, UK – 97% lead from ingestion & 3% from inhalation for 2 year old children (Davies et al., 1990)

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Food/water

Mining

Smelter

Natural environment

House yard

(US EPA, 1994)

Example of Lead Sources and Metabolism

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Exposure Pathways Dermal Absorption – very minimal impact Inhalation - Air-borne dust (-150 µm soil fraction) inhale,

cough-out then swallow Ingestion - Hand-to-mouth activity (-250 µm soil fraction)

Adult: 25 mg/day Child-Youth (>5 -15y): 50 mg/day Young Child (>0 - 5y): 100 mg/day Pica: 10 g/day

Dermal IngestionInhalation

Hand to mouth(<250 µm)

Thoracic(<10 µm)

Respirable(<2.5 µm)

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Lead via Ingestion Pathway

The Integrated Exposure Uptake Biokinetic (IEUBK) model by US EPA: default value used for children is 30%.

Ingestion: Hand-to-mouth activity (<250 µm soil fraction)

Adult: 25 mg/day Child-Youth (>5 -15y): 50

mg/day Young Child (>0 - 5y):

100 mg/day Pica: 10 g/day

Human GI track

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Stokes’ Law applied to particles (D>1.5 µm) (Finlayson-Pitts and Pitts Jr, 2000)

Where:v is the particle velocity (m/s); g is the gravitational acceleration (9.8 m/s2 at sea level);ρp is the mass density of the particles (kg/m3);ρair is the air density (1.2 × 10-3 g/cm3 at 20 and 1 atm pressure)℃D is the particle diameter (m);η is the gas viscosity (0.00001837 Pa s).

High wind speed

Low density

Distance

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PM10 (particulate matter <10 µm ） PM2.5 (particulate matter <2.5 µm ） PM250 - ingestion (hand to mouth)

Hand to mouth(<250 µm)

Thoracic(<10 µm)

Respirable(<2.5 µm)

(Modified from SKC Inc.)

Importance of particle size

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National Environment Protection (Ambient Air Quality) Measure (Air NEPM) standards and EPA Air EPP goal (EPA 2006 and NEPC 2003)

Pollutant Averaging period

Air NEPM Standards

2008 goal maximum allowable exceedances

Particles as PM 10

1 day# 50 µg/m³ 5 days a year

Particles as PM 2.5

1 day¶

1 year25 µg/m³8 µg/m³

Goal is to gather sufficient data nationally to facilitate a review

of the Advisory Reporting Standards as part of the review

of this Measure scheduled to commence in 2005.

Lead 1 year 0.50 µg/m³ No goal specified

Particles (visibility-

reducing)—Air EPP

1 hour 20 km visibility

No goal specified

# not to be exceeded more than five days per year ; ¶ NEPM Advisory Standard

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Lead in Environment

Lead minerals: galena (PbS) (primary), anglesite (PbSO4), cerrusite (PbCO3), massicot (PbO), litharge (PbO), leadhillite (Pb4(SO4)(CO3)2(OH)2)), Pyromorphite, (Pb5(PO4)3Cl), and Pb silicate.

Artificial lead from smelting: fine galena particles, PbO, Pb

Plumbogummite, plumbojarosite, goethite absorbed lead, and humic acid absorbed Pb in environmental samples.

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Background to Environmental Monitoring

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Background to Environmental Monitoring

• Identify and characterise hazardous chemicals• Assess risks posed by hazardous pollutants on

human health and the environment and risk associated with the cycle of hazardous wastes

• Apply fundamental principles of waste management and risk management to manage contaminated sites

• Develop a fundamental understanding of principles of waste management

• Strategies for waste minimisation

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Mining2 main processes

• Mining• Mineral Extraction Process• Other separation process

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Phases of Mining(plan at the start)

• Pre-mining• During mining• Post mining• Rehabilitation• Future land use

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Waste Production from Mining

– Mining– Mine waste dumps– Mineral extraction process– Mine tailings

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Environmental Sampling at Mine or Contaminated Sites

•Monitoring programs involving sampling of water, noise and dust are generally mandatory, at least in the initial stages of the mining venture

•Environmental Impact Statement (EIS) initiated programs

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Environmental Sampling at Mine SitesResults from monitoring programs assessed by mining company and those regulatory agencies with appropriate expertise as part of the review of the Annual Environmental Management Report (AEMR)

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Environmental Sampling at Mine Sites Basic Aims of Sampling

Program objectives• Determinands of interest • When, where and how for sampling• Testing methods to be used• How sample taken and preserved• Reporting of results• What happens to reported results

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Design of a SamplingProgram (Based on Maher et al., 1994)

Sampling hypothesis needs to be statedConsider: Problem/Question

ObjectivesModelIndicatorsHypothesis

Sampling Scheme relates to theSampling Objectives and Hypothesis by

considering: Cost Effectiveness

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Framework for designing a sampling program

PROBLEM / QUESTION

OBJECTIVES

MODEL

INDICATORS

HYPOTHESES

COSTEFFECTIVENESS

SAMPLINGSCHEME

site selection frequency replication

FIELD COLLECTION

qualityassurance

collectiondevice

storage /transport

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Primary SamplingApproaches

Approach RelativeNumber

ofsamples

RelativeBias

Basis ofSelecting

Sampling Sites

Judgemental Smallest Largest Prior history,visual

assessment oftechnical

judgementSystematic Larger Smaller Consistent grid

or pattern

Random Largest Smallest Simple randomselection

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Environmental Sampling

• Results from analysis of samples used to decide exceedances of environmental guidelines

• Validity of sample taking/sample analysis

• Not possible to transform bad (non - representative sample into good sample

• Sampling must be carried out with strict adherence to relevant sampling standards

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Sampling approaches

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Standard Methods• AS (1990) AS3580 9.6, Methods for Sampling and

Analysis of Ambient Air, Method 9.6: Determination of Suspended Particulate Matter-PM10 High Volume Sampler with Size-Selective Inlet-Gravimetric Method, and 9.7: Determination of Suspended Particulate Matter-PM10 Dichotomous Sampler-Gravimetric Method, Standards Association of Australia, Strathfield NSW.

• AS (2000) AS 4874 “Guide to the investigation of potentially contaminated soil and deposited dust as a source of lead available to humans”. Standards Association of Australia, Strathfield NSW.

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Fall –out collectorMicrovol PM 10

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Comprehensive air monitoring station

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High Volume Air Sampler

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PM 10 Collector

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Low volume PM 10 collectors

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Microvol PM 10

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Lead concentration (µg/m3) in particle as PM10 at the 5 monitoring stations

PM10 Pb Annual Moving Average

0

0.1

0.2

0.3

0.4

0.5

0.6

5/01/2005 5/01/2006 5/01/2007 5/01/2008 5/01/2009

Pb c

once

ntra

tion

(µg/

m3 )

BSD K Oval Miles St Racecourse RSL

Air NEPM standard

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Analytical approaches

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SAMPLE PREPARATION:3. Open the cassette filter holder and with forceps remove the sample filter. Fold the filter into quarterstaking care not to lose any sample, and transfer to a clean, 50-mL hot block digestion tube.4. Add 1.25 mL HCl. Cover with a plastic watchglass. Place in the hot block and heat at an internaltemperature of 95 /C for 15 minutes.NOTE: The internal temperature may vary from the digital readout. Calibrate the hot block prior todigestion.5. Remove the sample from the hot block and cool for 5 minutes. Remove watchglass and add 1.25 mLHNO3. Replace watchglass and return to hot block at 95 /C for 15 minutes.6. Remove the sample from the hot block and cool for at least 5 m inutes. Rinse watchglass into the samplecontainer and discard watchglass.7. Dilute to 25-mL final volume with distilled, deionized Type II water..

Preparation for analysis of heavy metals

– NIOSH Method 7303 2003

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Keep filter samples covered to prevent loss

Remove fall-out material, transfer to container and weigh

Send to laboratory for sample digestion and analysis by ICP-OES and /or ICP-MS

Following Collection

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SUMMARY

• Significance of metals and metalloids as contaminants

• Toxicology and Risk Assessment• Guidelines for Soil and Air• Issues and Exposure Pathways• Background to Environmental

Monitoring• Sampling Design and Analysis