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Protocol for the Derivation of Environmental and Human ... - CCME

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Part C, Section 1<br />

Geographical uncertainties include:<br />

• national <strong>and</strong> regional differences,<br />

• <strong>the</strong> difference between urban <strong>and</strong> rural environments,<br />

• local proximity to pollution sources, <strong>and</strong><br />

• individual lifestyles.<br />

Temporal uncertainties include:<br />

• <strong>the</strong> effects <strong>of</strong> changing measurement techniques, <strong>and</strong><br />

• uncertainties arising from using earlier data when pollution controls were less strict than today.<br />

Toxicokinetic uncertainties include:<br />

• possible differences in both intake <strong>and</strong> uptake,<br />

• toxic effects associated with different routes <strong>of</strong> exposure, <strong>and</strong><br />

• some substances may exist in different chemical <strong>for</strong>ms in different media.<br />

Analytical uncertainties include:<br />

• <strong>the</strong> inevitable errors in measurement,<br />

• <strong>the</strong> limitations <strong>of</strong> different techniques, <strong>and</strong><br />

• <strong>the</strong> representativeness <strong>of</strong> <strong>the</strong> samples analyzed.<br />

Philosophical or sociological uncertainties include:<br />

• questions about <strong>the</strong> nature <strong>and</strong> purpose <strong>of</strong> guidelines, <strong>and</strong><br />

• how far society might go to safeguard groups particularly at risk.<br />

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