Difference between revisions of "Exposure assessment"

Revision as of 19:28, 15 June 2011

General Overview

Exposure assessment involves a combination of methods and parameters to determine the dose of pathogens that hosts are exposed to. Aspects include:

• Shedding of pathogens by infected individuals
• Inactivation of pathogens over time on various surfaces, in water, or in food
• Transfer of pathogens between hands and objects
• Amount of air inhaled, water ingested, or foods ingested
• Settling of pathogens suspended in fluids

Water Exposure

Drinking Water Exposure

For a more complete description of the drinking water environment please refer to the Drinking Water page

^a Detailed data is given on page 3-25 of Chapter 3 in the EPA Exposure Factors Handbook

Children's ingestion rate for 4-8 years of age is 1,363 +/- 333 ml per day (mean +/- standard deviation) as given on page 3-64 of Chapter 3 in the EPA Exposure Factors Handbook

Recreational Water

For a more complete description of the recreational water environment please refer to the Recreational Water page

^b Detailed data is given on page 3-81 of Chapter 3 in the EPA Exposure Factors Handbook

Wastewater

For a more complete description of the wastewater environment please refer to the Wastewater page

Pathogen Specific

Regrowth

Shedding

Healthy population fecal output

1. Healthy Nigerian children aged 6 months to 5 years: mean 109.3 mL of stool per day (SD: 54.07). (Akinbami et al. 1995).

2. Healthy Nigerian adult (medical students): mean wet weight of 143.3 g stool per day (SD: 48.5), and an average of 0.89 stools per day.

E. coli H 10407

Healthy adult volunteers following ingestion of 10⁸ organisms given with NaHCO3: E. coli challenge controls were excreting approximately 10⁸ E. coli H 10407 organisms per gram of stool for seven days (Levine et al. 1980).

Diarrhea

1. 3-24 month children with diarrhea: During initial 24h and rehydration period, mean stool output was 126 (SD 33.6) grams of feces per kilogram body weight per hour (Dutta et al. 2000)

2. Adult Tunisian with acute diarrhea: mean stool weight 499 g per day (SD 284) (Hamza et al. 1999)

EPEC

Adult infected with EPEC: average stool weight 406.3 g per day (SD 300.2) (Donnenberg et al. 1993)

Survival

Transport

Case Studies

Air Exposure

Indoor Air

Outdoor Air

Pathogen Specific

Case Studies

Tao Hong, Yin Huang, Patrick L. Gurian and Charles N. Haas have completed a manuscript with complete fate and transport model coupled with dose response for indoor air release and fomite interaction of office inhabitants

Fomites

Ingestion

Membranes

Cutaneous

Besides exposure assessment, the other major components of microbial risk assessment are hazard identification, dose response assessment, and risk characterization.

References

EPA Exposure Factors Handbook

Akinbami, F., Erinoso, O. and Akinwolere, O. (1995) Defaecation pattern and intestinal transit in nigerian children. African Journal of Medicine and Medical Sciences 24, 337-341. Abstract

Donnenberg, M., Tacket, C., James, S., Losonsky, G., Nataro, J., Wasserman, S., Kaper, J. and Levine, M. (1993) Role of the eaea gene in experimental enteropathogenic escherichia coli infection. Journal of Clinical Investigation 92, 1412-1417. Full text

Dutta, P., Dutta, S., Manna, B., Chatterjee, M. and De, A. (2000) Hypo-osmolar oral rehydration salts solution in dehydrating persistent diarrhoea in children: Double-blind, randomized, controlled clinical trial. Acta Paediatrica 89, 411-416. Full text

Hamza, H., Ben Khalifa, H., Baumer, P., Berard, H. and Lecomte, J.M. (1999) Racecadotril versus placebo in the treatment of acute diarrhoea in adults. Alimentary Pharmacology and Therapeutics 13, 15-19. Full text

Levine, M., Rennels, M., Cisneros, L., Hughes, T., Nalin, D. and Young, C. (1980) Lack of person-to-person transmission of enterotoxigenic escherichia coli despite close contact. American Journal of Epidemiology 111, 347-355. Full text