Lehigh Med Summer 2019 - 15

L C M E D S O C .O R G

Diarrheal RWIs are of particular concern. It has been estimated that
on average a person has about 0.14 grams of feces on their buttocks.
These feces can wash off the person and enter the water at an aquatic
venue. If an individual is or has recently been sick, they may be shedding
millions of pathogens in their stool. Cryptosporidium may be shed in
the stool of an infected individual for up to two weeks after symptoms
resolve. Ingestion of this contaminated water (generally accidental) can
cause illness in others.
Some pathogens are readily killed by chlorine. Two notable exceptions
are the pathogenic parasites giardia and cryptosporidium. Both appear in
the top ten list of RWIs. Giardia can survive for up to 45 minutes even
in a properly chlorinated aquatic venue. The parasite cryptosporidium,
encased in a tough protective shell, can survive for days. It is little wonder
that it is #1 on the top ten list of RWIs:
TABLE 1: RANKING CAUSES OF RECREATIONAL WATER ILLNESSES
RANK

PATHOGEN

PATHOGEN TYPE

MODE

Cryptosporidium

Parasite

Gastrointestinal

Pseudomonas

Bacteria

Dermal

Shigella

Bacteria

Gastrointestinal

Legionella

Bacteria

Respiratory

Norovirus

Virus

Gastrointestinal

E. Coli

Bacteria

Gastrointestinal

Giardia

Parasite

Gastrointestinal

Disinfection agents and their byproducts

N/A

Various

Avian schistosome

Parasite

Dermal

Leptospira

Bacteria

Various

This underlines the need for the proper operation of aquatic venues,
an important aspect of which is the exclusion of ill and recently ill
individuals from the venue. Additionally, disinfectant and pH levels
must be maintained in the acceptable range and filtration must be
operational. Where Pennsylvania's Public Bathing Place Law is the
regulation of authority, the free chlorine residual in a pool or spa must
be maintained at or above 0.4 ppm and the pH must be maintained
between 7.2 and 8.2. The turnover period (the amount of time it takes

for a volume of water equal to the volume of the pool to be passed
through the filtration system) may not exceed 8 hours for swimming
pools and 2 hours for wading pools.
If a county or municipality has adopted its own local ordinance, these
values may be more restrictive. In 2007, two large outbreaks and five
smaller outbreaks resulted in 136 identified cases of cryptosporidium
in Montgomery County, PA. The Pennsylvania Department of Health
released their updated "Public Swimming and Bathing Places Operational
and Biological Contamination Protocol Recommendations," in part, to
address cryptosporidium concerns. Montgomery County passed a local
ordinance which is more stringent than Pennsylvania's Public Swimming
and Bathing Places Law. Check with your county or municipality to
see if there is a local ordinance in place.
The Model Aquatic Health Code (MAHC), the result of a collaboration led by the CDC between public health, the aquatics sector, and
academic partners from across the United States, is a good reference for
information on proper aquatic venue operation. The information found
in the MAHC is current and represents the latest in scientific research and
best practices. According to the MAHC, the free chlorine residual (parts
per million) in an aquatic venue should be maintained between 1.0 and
10.0 ppm (2.0 and 10.0 ppm if a chlorine stabilizer is used) and 3.0 to
10.0 ppm if the aquatic venue is a spa. The pH should be maintained
between 7.2 and 7.8. The MAHC recommended turnover periods
vary greatly by aquatic venue type, but none is longer than six hours.
Some aquatic venues use bromine instead of chlorine as the primary
disinfectant. According to the MAHC, bromine concentrations in an
aquatic venue should be maintained between 3.0 and 8.0 ppm and 4.0
to 8.0ppm if the aquatic venue is a spa. Additionally, aquatic venues
may also employ a form of secondary disinfection. Some examples of
secondary disinfection are UV light, ozone and copper/silver ions.
There are other popular places to cool off in the summer. Many
individuals swim in natural bodies of water such as oceans, lakes and
Continued on page 16
SUMMER 2019 | Lehigh County Health & Medicine 15

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Lehigh Med Summer 2019

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