Part III Lecture 4

Question 1

Indirect methods of exposure assessment

Answer 1

• Environmental monitoring (proximity, regional monitors)

- Questionnaires/diairies

Question 2

Direct methods of exposure assessment

Answer 2

• Biological monitoring (e.g., blood, urine)

- Personal monitoring (personal exposure)

Question 3

What is the role of exposure science?

Answer 3

Collect qualitative and quantitative information to understand the nature of contact between humans and stressors

Question 4

Objective of exposure assessment?

Answer 4

Estimate uptake of external agent resulting from the contact with an environmental medium (intensity, duration, frequency)

Question 5

What is the dose? How does it relate to exposure?

Answer 5

Dose: what is actually absorbed/deposited in the body

- exposure is a surrogate measure of dose

Question 6

What is the exposome?

Answer 6

The combined exposures from all sources that reach the internal chemical environment
- Complements the genome by providing a comprehensive description of lifelong exposure history

Question 7

Biomonitoring - Dis/Advantages?

Answer 7

ADVANTAGES

• Provides a measure of internal dose integrated over multiple sources (food, water, air)
• Different tissues/fluids reflect different timing of exposure (e.g., total dose vs recent)

DISADVANTAGES

• Problematic if impacted by disease status
• Costly

Question 8

What is biomonitoring?

Answer 8

Assessment of human exposure to an environmental chemical by measuring a biological marker of exposure

e.g., blood, urine, breast milk, saliva, hair, teeth, adipose

Question 9

Preferences in characteristics of biological markers?

Answer 9

1. Chemical-specific
2. Detectable in trace quantities
3. Non-invasive
4. Inexpensive
5. Relate to the extent of exposure (consistently and quantitatively)
   Ideally: integrates exposure over time

Question 10

What are biological pathways? Why are they important for exposure science?

Answer 10

They link exposure and disease

• exposures can be measured at various points along this pathway
• provides an understanding or an hypothesis as to how exposure contributes to the disease, so that we can select an exposure that has good: timing, frequency/intensity, route

Question 11

Available dose?

Answer 11

Dose available in the external media

Question 12

Intake?

Answer 12

Amount of available dose in contact with human body

- influenced by time-behaviour patterns of host

Question 13

Absorbed dose?

Answer 13

Dose that actually enters body

- Influenced by host factors (e.g., genetics, metabolism)

Question 14

Active dose/biologically effective dose?

Answer 14

Dose that reaches the active site in the body that ultimately leads to the disease

Question 15

What is the true exposure?

Answer 15

The causal agent of interest over the relevant time-period specific to the disease of interest
- since it can rarely be measured, we need to operationalize it (define it in terms of an exposure that can be measured)

Question 16

Aetiological exposure time window?

Answer 16

Time period during which exposures are most relevant to the development of the disease

• we often need to estimate the exposure many years in the past
• we rarely know what the specific time window is

Question 17

Induction period?

Answer 17

Interval of time between the end of the aetiological time window and the onset of the disease

Question 18

Latent period?

Answer 18

Time between the onset of the disease until the diagnosis

Question 19

What is the problem with exposures during the latent period?

Answer 19

Exposure during the latent period can be influenced by the disease (e.g., symptoms may change behaviour)
- Giving rise to reverse causality