2. Vinculo Aguas Residuales-Tim O'Shea

8/19/2019 2. Vinculo Aguas Residuales-Tim O'Shea

1/19

Wastewater and Health

Tim O’Shea MD, FRCPC, MPH

Associate Professor

Department of

Medicine

McMaster University,


2/19

Outline

• Wastewater and Health – The Canadian

context

• Health effects

of

wastewater

– focus

on

infectious diseases

• Implications for

Peru

and

future

directions


3/19

Wastewater and

Health

• In May 2000 the drinking water supply in

Walkerton Ontario

became

contaminated

with

E. coli

• The

local

water

supply

was

sourced

from

groundwater which was exposed to run‐off

from a cattle farm after particularly heavy rain

fall


4/19


5/19

Walkerton Tragedy

• The result of this contamination was several

thousand acute

gastrointestinal

illnesses,

7

deaths and many individuals left with long

term illnesses

• Resulted in criminal charges against

individuals responsible

for

water

system


6/19

Wastewater and

Health

• The use of wastewater for agricultural

irrigation has

several

potential

benefits:

– Release

of

higher

quality

sources

for

alternative

uses

– Increase water supply

– Provide nutrients

for

fertilization


7/19

Wastewater and

Health

• The main risks associated with wastewater use

are related

to

public

health:

– Presence of bacterial, viral, protozol or heminthicpathogens

– Presence of

chemicals/pesticides

and

potential

for

health effects

• The risk

of

wastewater

use

is

exacerbated

when its use is unintentional or indirect


8/19

Wastewater and

Health

• Indirect use occurs when treated, partially

treated or

untreated

wastewater

enters

the

agricultural irrigation system

• Health risks are similar with planned and

unplanned wastewater use but when

unintentional systems

to

mitigate

risk

are

usually not present


9/19

Infectious Diseases

• Human feces contain ~ 1010 bacteria per gram,

the majority

of

which

are

non

‐pathogenic

• In the setting of infection with gastrointestinal

pathogens, stool

will

contain

large

quantities

of

the infecting organism

• Gastrointestinal illness

such

as

cholera,

typhoid

and E. coli O157:H7 can all be passed through exposure to contaminated water


10/19

Infectious Diseases

• Viral pathogens can also be important causes

of water

borne

illness,

particularly

hepatitis

A

virus, adenoviruses, enteroviruses and

noroviruses

• Parasitic infections, especially helminthic

infections whose

life

cycle

includes

a soil

phase, are particularly important in

discussions of wastewater and health


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12/19

Wastewater and

Health

• Important to remember that health risks are

present both

for:

– Agricultural

workers

exposed

to

pathogens/toxins

in wastewater

– Those who

eventually

consume

potentially

contaminated foods


13/19

Wastewater and

Health

• Overall risk to human health depends on:

– Excreted load

– Ability of organism to persist in environment

– Minimum infectious dose

– Ability of organism to enter latency

– Response of

human

host

(influenced

by

possible

immunity)


14/19

Wastewater and

Health

• Given these factors most models rank relative

importance of

infectious

agents

as

follows:

1. Helminth infections

2. Protozoal and bacterial infections

3. Viral infections


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16/19

FIGURE 3. Prevalence of diarrhea in Peruvian children aged 0–35 months, 1995–1998.

William Checkley et al. Am. J. Epidemiol. 2003;157:166-175

©2003 by Oxford University Press


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18/19

Wastewater in

Peru


19/19

Questions?

[email protected]

2. Vinculo Aguas Residuales-Tim O'Shea

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