**6. Quantitative microbial risk assessment for** *Giardia* **in environmental samples**

The QMRA is an approach that has been widely used around the world to estimate the risk of infection by giardiasis in different sources of exposure. Most research studies have been performed in water samples, but the method has been applied in food, soil, and air samples.

In the last few years, the most relevant studies where QMRA has been used to evaluate giardiasis infection risks are the following:

In New Jersey, USA, the risk by accidental water ingestion (50 mL) of the Lower Passaic River was assessed resulting in a probability of 1:1 [23]. In Amsterdam, risk probability was calculated from 9 × 10−4 to 1.2 × 10−2 in recreational waters [63], while in Eastern Europe a giardiasis risk was predicted from 3 × 10−1 for water consumption from a well contaminated with sewage water [64]. In Mexico, a risk of 1.09 × 10−2 was estimated by lettuce consumption [65].

In France and England, *Giardia* risks were assessed due to water consumption from private well with values from 5.8 × 10−1 and 5.7 × 10−1, respectively [60]. Risk for swimming in recreational waters of the Great Lakes in the USA was 5 × 10−3 [66]. The risk for rainwater consumption was also calculated in Australia at 3.1 × 10−1 [67].

In Brazil, giardiasis risk for drinking water consumption was estimated at 1.92 × 10−2 [68]. In Venezuela, the risk for bathers swimming in seawater was 3.6 × 10−2 [69]. In Switzerland, the risk by indirect contact with water from a lagoon contaminated with residual water was 3.5 × 10−1 [70], whereas risk by joint exposure to soil and dust transported by air was assessed at 1:1 in a rural town in Mexico [17].

In all the previous studies (**Figure 2**), the risks were greater than those allowed by the regulating commissions (1 × 10−4), which is why these studies show that the microorganism concentration is enough to produce the disease in a percentage of the populations.

#### Risk Assessment for *Giardia* in Environmental Samples http://dx.doi.org/10.5772/intechopen.70805 155

Quantitative microbial risk assessment has become a standard; the UK has pronounced a mandate that establishes that risk assessment be carried out by local government on many water supplies [60]. The US Environmental Protection Agency (EPA) handled permissible water *Giardia* risk values of <1:10,000 (10−4) in a yearly exposure [61]. In the UK, the Water Supply Regulations 1999, and The New Dutch Drinking Water Decree state that for pathogenic microorganisms, health risk should be less than 1 infection/10,000 consumer/ year [62]. These risk regulations are equal to those of EPA. Developed countries are in the position to provide guidance, training, information resources, and technical assistance to advance supports for water safety. Thus, greater cooperation and collaboration at all levels should be effective and ensure that QMRA, as a water safety tool, will be available to all

**6. Quantitative microbial risk assessment for** *Giardia* **in environmental** 

The QMRA is an approach that has been widely used around the world to estimate the risk of infection by giardiasis in different sources of exposure. Most research studies have been performed in water samples, but the method has been applied in food, soil, and air

In the last few years, the most relevant studies where QMRA has been used to evaluate giar-

In New Jersey, USA, the risk by accidental water ingestion (50 mL) of the Lower Passaic River was assessed resulting in a probability of 1:1 [23]. In Amsterdam, risk probability was calculated from 9 × 10−4 to 1.2 × 10−2 in recreational waters [63], while in Eastern Europe a giardiasis risk was predicted from 3 × 10−1 for water consumption from a well contaminated with sewage water [64]. In Mexico, a risk of 1.09 × 10−2 was estimated by lettuce consump-

In France and England, *Giardia* risks were assessed due to water consumption from private well with values from 5.8 × 10−1 and 5.7 × 10−1, respectively [60]. Risk for swimming in recreational waters of the Great Lakes in the USA was 5 × 10−3 [66]. The risk for rainwater consump-

In Brazil, giardiasis risk for drinking water consumption was estimated at 1.92 × 10−2 [68]. In Venezuela, the risk for bathers swimming in seawater was 3.6 × 10−2 [69]. In Switzerland, the risk by indirect contact with water from a lagoon contaminated with residual water was 3.5 × 10−1 [70], whereas risk by joint exposure to soil and dust transported by air was

In all the previous studies (**Figure 2**), the risks were greater than those allowed by the regulating commissions (1 × 10−4), which is why these studies show that the microorganism concentration is enough to produce the disease in a percentage of the populations.

countries.

154 Current Topics in Giardiasis

**samples**

samples.

tion [65].

diasis infection risks are the following:

tion was also calculated in Australia at 3.1 × 10−1 [67].

assessed at 1:1 in a rural town in Mexico [17].

#### **Figure 2.** Risks by giardiasis calculated by quantitative microbial risk assessment in different countries.


**Table 5.** Annual risks of Giardia infections in different regions in the world.

Based on this information, it should be solved how to make these sources not harmful for humans and implement the necessary treatments for decreasing or eradicating giardiasis risk.

Using the concentrations reported in the literature, annual risk by giardiasis was calculated. To estimate infection probabilities (P<sup>i</sup> ), a consumption exposure of 1.46 L was taken into account [71], and then the exponential model equation P<sup>i</sup> = 1−exp(−*rN*) was used where *r* = 0.0199 [72] (**Table 5**).
