Perspectives on prioritizing microbial hazards and quantifying risks for produce safety. Jeffrey Soller Water Summit February 27, 2018

Transcription

1 Perspectives on prioritizing microbial hazards and quantifying risks for produce safety Jeffrey Soller Water Summit February 27, 2018

2 Outline Overview of Risk Analysis Risk Considerations for Produce Safety Which hazards What public health endpoint (infection / illness / DALY) Exposure Approaches to characterize risk (qualitative / relative /quantitative) Perspectives on Microbial Risks of the Produce Safety Rule Standards for Agricultural Water Numeric standards (NS) review Basis for NS Level of public health protection associated with NS SLPHP 2

3 Risk Analysis Overview

4 Risk Analysis Framework 4

5 Risk Management has to account for many considerations and many perspectives 5

6 Considerations for Produce Safety Risk (Risk Assessment)

7 Which microbial hazard(s)? Outbreaks 7

8 Which microbial hazard(s)? Illnesses in the Community 8

9 What units to evaluate public health risk? Infection Example: Use of recycled water for potable purposes in the US is moving toward a benchmark risk level of 1 infection /10,000 people yr -1 Illness Example: Recreational water in the US is based on a level of protection of 32 or 36 gastrointestinal illnesses per 1,000 recreation events Health burden Example: WHO Guidelines for Safe Drinking set the tolerable burden of disease as an upper limit of 10-6 Disability Adjusted Life Years (DALYs) per person per year Advantages: 1) aggregation of different impacts on the quality and quantity of life and 2) focuses attention on actual outcomes rather than potential risks and thus, can support rational priority setting. Disadvantage: 1) Basis for calculations can be somewhat subjective and 2) can be difficult to explain 9

10 Exposure Route(s) of contamination Produce commodities are susceptible to microbial hazards before, during, and after harvest Possible routes of contamination Water Soil amendments Animals Workers hygiene Focus here on irrigation water and pre-harvest time period 10

11 Exposure to water as a route of contamination Water source Public water system Groundwater Surface water Stormwater runoff Application method Spray Subsurface irrigation Furrow irrigation Timing How long from the use of the water to consumer Crop Servings /acre % acreage irrigated % of water hits edible portion Die off in the field Die off /growth during storage Cross contamination from handling Consumption ml per serving 11

12 Exposure to water as a route of contamination 12

13 How to characterize risk Risk characterization integrates and synthesizes information to convey the nature, existence, and extent of human health risks Complete Informative Useful for decision makers The risk characterization should be Transparent Clear Consistent Reasonable The analyses can vary in complexity Qualitative Relative Quantitative 13

14 Perspectives on Microbial Risk Aspects of the Produce Safety Rule Standards for Agricultural Water

15 Microbial Risk Aspects of the Produce Safety Rule Standards for Agricultural Water Review numeric standards and their basis Discuss level of public health protection and SLPHP 15

16 Numeric Standards 16

17 Science-based minimum standards 17

18 Agricultural water must be safe and of adequate sanitary quality 18

19 Requirements include analytical testing 19

20 Numeric Criteria 20

21 US EPA s 2012 recreational water quality criteria (RWQC) are the basis for the numeric criteria 21

22 US EPA s criteria for recreational waters were derived for a specific exposure scenario Recreation (swimming) in fresh and marine water Derived from epidemiological studies conducted in waters impacted by municipal wastewater effluent (treated and disinfected) Level of protection is explicit Allow for developing alternative criteria Epidemiology Quantitative Microbial Risk Assessment (QMRA) Alternative methods 22

23 The fecal indicator bacteria in the RWQC are imperfect 23

24 US EPA s criteria for recreational waters have a specific basis Recreation (swimming) in fresh and marine water Derived from epidemiological studies conducted in waters impacted by municipal wastewater effluent (treated and disinfected) Level of protection is explicit Allow for developing alternative criteria Epidemiology Quantitative Microbial Risk Assessment (QMRA) Alternative methods 24

25 US EPA s criteria for recreational waters have a specific basis Recreation (swimming) in fresh and marine water Derived from epidemiological studies conducted in waters impacted by municipal wastewater effluent (treated and disinfected) Level of protection is explicit Allow for developing alternative criteria Epidemiology Quantitative Microbial Risk Assessment (QMRA) Alternative methods 25

26 Level of Public Health Protection provided by the agricultural water numeric criteria 26

27 Level of Public Health Protection provided by the agricultural water numeric criteria FDA developed Quantitative Risk Assessment and provided example assessment for a series of scenarios Hazard: EHEC Crop: Lettuce Exposure Irrigation water via overhead sprinkler with a wide range of water qualities Health endpoints - Probability of illness and health burden (DALY) 27

28 Relative risks for the example scenarios 28

29 Relative risks for the example scenarios Predicted Cases per Acre Farm C Farm D Farm B Farm E 0.46 Farm F 1.21 Farm A

30 Same Level of Public Health Protection 30

31 An evaluation of the level of public health protection compared to the FDA requirement can widely vary Do data support a determination SLPHP? Are there any unique considerations to the level of public health protection? Was the evaluation conducted by competent individuals using appropriate processes? Is the determination of SLPHP properly documented? 31

32 Risk Analysis Framework 32

33 Questions / Comments / Thoughts