**3. Metal concentration and risk analysis to human health**


**Table 2** shows the concentrations of metals found in different organisms, which are the basis for determining the risk factor analysis; as expected, organisms such as bivalve mollusks from the Candelaria, Chumpan and Palizada rivers, show the

*Heavy Metal Contamination in a Protected Natural Area from Southeastern Mexico… DOI: http://dx.doi.org/10.5772/intechopen.95591*


#### **Table 2.**

*Heavy metals determined in different marine species.*


**National and international legislation governing the levels of heavy metals in marine mollusks and crustaceans in μg g<sup>1</sup>**


*1 JECFA, 1989 Evaluation of Certain Food Additives and Contaminants (Thirty-third Report of the Joint FAO/WHO Expert Committee on Food Additives) [meeting held in Geneva from March 21 to 30, 1988]. World Health Organization. 2 WHO, 1996. Health criteria other supporting information. In: Guidelines for Drinking Water Quality p. 31–388. <sup>3</sup> USFDA, 1993. Food and Drug Administration, Guidance for Nickel in Shellfish. DHHS/PHS/FDA/CFSAN/Office of Seafood, Washington DC, 1993.*

*4 NOM-242-SSA-2009. Products and services. Fresh, refrigerated, frozen and processed fishery products. Health specifications and test methods.*

*5 FAO,1983. Compilation of legal limits for hazardous substances in fish and fishery products Fish Circular 464:5–100. <sup>6</sup> NOM-242-SSA1–2009 Products and services. Fresh, refrigerated, frozen and processed fishery products. Health specifications and test methods.*

*7 USFDA, 1993. Guidance document for lead in shellfish. Center for Food Safety and Applied Nutrition. United States Food and Drug Administration, Washington, D. C.*

*8 Nauen C.E, 1983. Compilation of legal limist for hazardous substances in fish and fishery products. FAO fisheries circular 764. United Nations Food and Agriculture Organization. Rome, Italy, 102 pp.*

*9 ISSC,2007. National shellfish sanitation program. Guide for the control of molluscan shellfish. Interstate Shellfish Sanitation Conference. U.S. Food and Drug Administration, Department of Health and Human Services. Washington, D.C., 549 pp.*

#### **Table 3.**

*Permissible levels of heavy metals in fishery products.*

highest values in Cd, exceeding the limits established by the official Mexican Standards (NOM 242 and the USFDA standards **Table 3**). Likewise, Cu levels are high in clams *Rangea cuneata*, exceeding international specifications (**Table 3**); the Pb levels in *Ariopsis felis* exceed all the international specifications contemplated in this study. The reference values reported in national and international standards for heavy metals in marine fish and mollusks are shown in **Table 3**.

Concentrations of heavy metals in the macrophytes collected in "Arroyo La Caleta", where detected below the limit of quantification of the method (not detected ND) for B, Be, Fe, Mn and Si to 4671.29 μg g�<sup>1</sup> for Fe. The average concentration of the metals analyzed presented the following order: Be<As<V < Mn < B < Si < Fe. Of the three species of macrophytes studied, the one that presented higher concentrations of metals was *Cyperus ligularis L.* accumulating higher percentages of Be, Fe, Mn, Si and V, followed by *Typha domingensis* which presented the highest concentration of As and average concentrations of the other metals, finally, *Lemna minor*. Regarding the structure analyzed in plants, the highest concentrations were found in the roots and to a lesser extent in the stem and leaves, which tells us about the ability to translocate (mobilize) the metals to the aerial parts as a strategy of adaptation to pollution due to heavy metals. In general, the highest concentrations found in macrophytes were related to the sites of highest anthropogenic activity [36]. It should be noted that, of all the collection sites in the Términos Lagoon Natural Protected Area analyzed in this study, the "Arroyo La Caleta" is considered one of the most contaminated because it receives wastewater from Carmen City, which is why the fish products obtained there have not been considered suitable for human consumption for several years. Due to the above, the study of the behavior of heavy metals in this location, was based on organisms with high levels of adaptation to heavy metal pollution that are not used for human consumption.

## **4. Estimation of the estimated daily intake, target hazard quotient, hazard index and target cancer risk**

According to the USEPA [37–38] the estimate of potential risk to human health from the consumption of contaminated marine products is based on the estimated daily intake (EDI), the target hazard quotient (THQ), hazard index (HI) and target cancer risk (TR). The first parameter that was estimated is a function of the relation (EDI; μg kg�<sup>1</sup> week�<sup>1</sup> )

$$\text{EDI} = \frac{(\text{FIR})(\text{MC})}{\text{BWa}} \tag{1}$$

Where FIR is the food ingestion rate of fish or shellfish consumed by an adult; according to CONAPESCA, these data for Mexico, is up to 12 kg year�<sup>1</sup> or the equivalent of 230 g week�<sup>1</sup> for an adult with an average weight. For children aged 4 to 6 years, the recommended food ingestion rate is 100 grams per week (CONAPESCA: National Commission for Aquaculture and Fisheries, Fishery production statistics, www.conapesca.sagarpa.mx) or its equivalent of 5.214 kg year�<sup>1</sup> .

According to studies by Araneda [39] the population group of adolescents is the one that shows a lower food ingestion rate of these foods; there is no data on intake in Mexico, but the recommendations indicate that an average adolescent between 14 and 17 years of age should consume between 240 and 300 grams of fish and seafood per week, the equivalent of an average of 15. 64 kg year�<sup>1</sup> . Due to the

*Heavy Metal Contamination in a Protected Natural Area from Southeastern Mexico… DOI: http://dx.doi.org/10.5772/intechopen.95591*

scarcity of information in this population group, in this study it is considered that the average food ingestion rate for adolescents is 7.8 kg year�<sup>1</sup> , which is considered a low consumption and that represents a value of 150 gr week�<sup>1</sup> .

The parameter BWa is the reference body weight of an adult. In countries such as China, this data is 55 kg [40]; the average weight of a Mexican adult is 70 kg. The average weight for children between 4 and 6 years old is 16 kg [41] and for an average adolescent between 14 and 17 years old the weight considered is 54 kg. All the reference data are based on the characteristics and habits of the Mexican population without obesity problems. The MC parameter is the metal concentration (Cu, Pb, Ni, Hg) expressed in μg g�<sup>1</sup> .

The estimated results for the EDI parameter are shown in **Table 4**. With the data from the population intake rates, we can estimate the THQ parameter which is a dimensionless amount and a relationship between the concentration of heavy metals in ingested food with other factors. According to USEPA [37–38] the THQ value should not exceed the numerical value of 1. Estimated values below 1 indicate that the contaminant levels do not cause adverse effects or potential noncarcinogenic risks in exposed persons during the estimated average life span of the Mexican population of 70 years.

The model for estimating the target hazard quotient (THQ) is determined by Eq. 2. The units were adequate for not using correction factors (**Table 5**).

$$THQ = \frac{(E\circ r)(EDtot)(FIR)(MC)}{(R\circ d)(BWa)(Atn)}\tag{2}$$

Where Efr is the exposure frequency to the trace element, (365 days year�<sup>1</sup> ), EDtot is the exposure duration (average life span of 70 years), FIR is the food ingestion rate in grams per day for the respective food item (g day �<sup>1</sup> ), MC is the concentration of the trace element in the given food item (μg g�<sup>1</sup> ), Rfd: is the oral reference dose of the trace element (μg g-<sup>1</sup> day�<sup>1</sup> ) (5 � <sup>10</sup>�<sup>4</sup> for Hg; 1 � <sup>10</sup>�<sup>3</sup> for Cd; 4 � <sup>10</sup>�<sup>3</sup> for Pb; 2 � <sup>10</sup>�<sup>2</sup> for Ni and 4 � <sup>10</sup>�<sup>2</sup> for Cu), BWa is the reference body weight (g), Atn is the averaged exposure time (Efr x EDtot).

The values obtained show a variable trend among the reference population groups, with children aged 4–6 years being those with the highest values of EDI for Cu and Ni; these values are directly related to weight.

#### **4.1 Hazard index (HI)**

The accumulated risk was evaluated by the individual sum of each of the THQ factors which represent the risk index (HI), which is shown in Eq. 3. These values, like THQ, must not exceed the numerical value of 1, otherwise it could indicate that there are considerable risk factors for the consumption of marine products reported in this study.

$$\text{HI} = \sum \text{THQ} \tag{3}$$

According to the estimated results (**Table 6**) no value calculated for THQ and HI exceed the parameters established to consider a risk to health by the intake of these contaminants from the consumption of fish and seafood.

The results indicate that the estimated HI values do not represent a risk for the reference population, since they do not exceed the comparison value of 1.


*Heavy Metals - Their Environmental Impacts and Mitigation*

**Table 4.**

 *Estimated daily intake (EDI), taking as a reference a population group between adults and children of different age ranges.*


*Heavy Metal Contamination in a Protected Natural Area from Southeastern Mexico… DOI: http://dx.doi.org/10.5772/intechopen.95591*

> **Table 5.**

 *Estimated values of the target hazard quotient (THQ) in a reference population group.*


#### **Table 6.**

*Estimated values of the hazard index estimated for a reference population, expressed as the sum of all the individual HI factors.*

#### **4.2 Target cancer risk**

The risk from carcinogens was indicated in this study by the TR values (**Table 7**). For the estimation of these parameters, the values of Region III were taken, where the population of Mexico is included according to USEPA criteria [37–38]. The equation that represents risk for carcinogenic factors is represented by the following expression:

$$\text{TR} = \frac{(\text{Efr})(\text{EDI})(\text{FIR})(\text{MC})(\text{Cfo})}{(\text{BWa})(\text{Atn})} \tag{4}$$

Where TR is the target cancer risk (dimensionless factor) and Cfo is the oral cancer slope factor; USEPA criteria [42] (μg g�<sup>1</sup> bw day�<sup>1</sup> ). The other values are the same used for the estimation of EDI and THQ. In this study, the Cfo values used to estimate TR are 8.5 � <sup>10</sup>�<sup>3</sup> for Pb and 1.7 for Ni, a metal that is on the list of potent carcinogens [42]. The value of 2.59 � <sup>10</sup>�<sup>4</sup> was used for Cd which has been considered carcinogenic according to the International Agency for Research On Cancer (IARRC: http://www.iarc.fr/en/websites/index.php). Not all metals are considered within this classification so far; only Cd, Pb and Ni fall into this category. According to the New York State Department of Health [43] (NYSDOH) the categories of the target cancer risk (TR) are the following: TR ≤ 10�<sup>6</sup> low risk, between 10�<sup>4</sup> and 10�<sup>3</sup> moderate risk, from 10�<sup>3</sup> to 10�<sup>1</sup> high risk and TR ≥ 10�<sup>1</sup> very high risk that people may develop cancer at some point in their life after exposure to the metal.

The results of the target cancer risk for Cd and Pb show that the three study categories (adults, children, and adolescents) present a low risk of developing cancer from the ingestion of fish and shellfish. On the other hand, the target cancer risk calculated for Ni shows that the population group of children aged 4–6 years represents a very high risk, and a moderate risk is expected for adults and adolescents.

In certain cases, it is not advisable to limit the consumption of these marine products. It is more useful to be vigilant, as well as to limit the frequency of consumption when there is evidence of risk for the population. These actions make the difference in developed countries that have public policies and develop research *Heavy Metal Contamination in a Protected Natural Area from Southeastern Mexico… DOI: http://dx.doi.org/10.5772/intechopen.95591*


#### **Table 7.**

*Estimated values of the target cancer risk (TR) in a reference population.*

through environmental agencies to develop models that can be applicable to different regions of the world and thus predict or estimate possible risks.

There are general recommendations in Mexico regarding the consumption of fish and seafood by children under four years of age. Certain countries such as Canada restrict consumption of species caught in rivers and lakes and recommend that consumption in the population group of children 1–4 years old be only 75 g month�<sup>1</sup> and in children 5–11 years old be 125 g month�<sup>1</sup> , as well as that pregnant women should not consume more than 150 g month�<sup>1</sup> [44]. Some of these recommendations are in most cases based on economic interests.

Bellanger et al. [44], analyze in their studies the economic implications of exposing a population group to the toxic effects of heavy metals. In Mexico, consumption of fish and seafood is lower than that of other foods. In Mexico, fish products are governed by Mexican standards that limit the presence of heavy metals in their products; likewise, government institutions regulate the health of oyster and clam banks (due to the presence of pathogenic microorganisms), but there are no effective public policies focused on protecting the environment, stopping the deterioration of mangrove areas or monitoring and sanctioning poaching and depredation that are putting numerous species at risk.

#### **5. Conclusions**

Throughout this chapter, aspects of the region of the Campeche Sound were shown, and in particular the Terminos Lagoon, which only a decade ago produced more than 80% of the national production of crude oil, while at the same time numerous marine species of high commercial value were extracted from its waters. Today, even though oil activity has decreased considerably, the effects of this industry, combined with population growth and the ineffectiveness of monitoring programs, still persist. The results of this study of the concentrations of heavy metals in *Crassostrea virginica*, *Rangea cuneata* and *Ariopsis felis* indicate that some of the values found are higher than those established in international and national legislation, so these fish products should not be consumed. The establishment of a monitoring program is suggested to identify the variations and conditions that favor the bioaccumulation process in exposed organisms.

Regarding the risk analysis carried out in this study, the values calculated for the target hazard quotient (THQ) and the hazard index (HI) indicate that the consumption of the studied species does not represent a risk for human health in any of the considered age groups; however, in relation to the TR that evaluates the potential risk for carcinogens, the results show worrying values, especially for the organisms that come from the Pom-Atasta lagoon system. In the two species evaluated (*Rangea cuneata* and *Ariopsis felis*), the TR values are considered "high risk" and "moderate risk", especially in the most vulnerable population group, children. For this reason, it is not recommended the consumption of these species by children under 4 years old and it is suggested to decrease their consumption in the adult and adolescent age groups. These actions are not intended to stigmatize the consumption of these products, but to have greater control and surveillance, especially in population groups of greater vulnerability.
