Results
Case 1: Environmental health risk assessment of fire fighting foam containing PFOA that leach into groundwater
Step 1: identify the issue (Issue identification)
XXfield is a small town in New Zealand; the residents recently discovered presence of firefighting foams in their groundwater. Firefighting foams contain PFOA that are known to be endocrine disruptors. If people were to continue to consume drinking water that contained PFOA, what would be their health risks due to such contamination? What needs to be done?
Step 2: Identify the hazard (Hazard Identification)
- Man-made chemicals found in fire-fighting chemicals
- Most people get exposed to PFAS through drinking water
- Eating food, and drinking water, (here, we will consider only from drinking water)
- No specific health effects, thyroid disease, liver damage,
- Non-cancerous health effects? IARC labels as probably carcinogenic, hence we will analyse non-cancerous health effects
- Drinking water value: 0.07 ug/L
Step 3: Assess the exposure (Exposure assessment)
- A survey conducted locally found that the levels of PFOA locally in a few samples of water just exceeded the Australian drinking standards.
- On this basis, let us assume that for those water sources, the levels were 0.07 ug/L
- For most of the other wells, the levels were within the Australian standards accepted for NZ national standards
Step 4: Assess the relationship between dose and health effects (Dose response assessment)
Tolerable daily intake: 0.02 ug/Kg/day from the EPA standards.We will use the TDI as equivalent of ADI (acceptable daily intake). As none of our health effects are carcinogenic, therefore we have not taken into account any slope factor for the health effect. Had that been the case, we would use the slope factor. Slope factors are used for cancers. TDI (synonymous with ADI or Rfd) is given as NOAEL/Uncertainty Factor but for us here it is already estimated for us 0.02 ug/Kg/dayWe will assume the daily intake for a 70 kg person with 2L water consumption per dayWe assume that water would be the only way PFOA can enter the bodyStep 5: Characterise the risk (Risk characterisation)
We will characterise the risk in two ways:
First, compare exposure in terms of mg/kg of Body weight/day does it to the Rfd that has been established in the dose-response estimation step. If current exposure exceeds Rfd, then current exposure:Rfd ratio will exceed 1.0
Second, estimate the amount of media (water, food etc) one must consume so that the health effect will manifest.
Scenario 1: Relationship between current exposure and Rfd
- Assuming that 0.07 ug/L of PFOA were identified in the sample, then for a 70 kg person with daily 2L of water intake
- A 70 kg person who consumes 2L of water per day would consume 0.14 ug/day
- The weighted daily intake for such a person would be: (0.14 ug/day) / 70 kg = 0.002 ug/kg/day
- This is 1/10 the TDI (0.02 ug/kg/day).
- For a 60 kg weighted person, this would be: 0.14 ug/day / 60 kg = 0.0023, ~ 1/10 th tolerable limit
Scenario 2: How much water should a 70-kg person consume every day for say 5 years before the clinical signs appear
- If a person weighing 70 kg were to consume 1 L of water containing 0.07 ug/L of PFOA (as found in this exposure scenario), then the person would have 0.001 ug/Kg/day of intake
- To match 0.02 ug/Kg/day, the person would have to drink about 0.02 / 0.001 = 20 litres of water per day. As no one consumes that quantity of water on a daily basis, therefore the risks are not likely to be realised.
Risk Mitigation:
Based on this estimate, we can state that at the levels detected in the wells of the households, exposure to such concentrations of PFOA is not likely to lead to major health effects that we know as of the present time. However, the levels should be monitored.
Case 2: Environmental health risk assessment of inorganic arsenic in drinking water
Step 1: Issue identification
In the West Bengal state of India, in the early 1980s, people reported to doctors and skin clinics with signs of chronic arsenic toxicity; this included skin lesions with raised and painful lesions. Exposure to inorganic arsenic also results in cancers of urinary bladder and lungs.
Step 2: Hazard identification
Inorganic arsenic is a metal dissolves in groundwater. Route of entry through oral ingestion of water and food cooked in the water. Arsenic has both cancerous and non-cancerous health effects. Non-cancerous health effects include skin lesions. Cancerous health effects include skin cancer, bladder cancer, and lung cancer.
Step 3: Dose response effect