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7.0 STANDARD LIMIT / GUIDELINES FOR PAH IN THE ENVIRONMENT:
The united states environment protection agency (USEPA, 1990) has classified PAHs with B(a)P indicator species as a B-2 pollutant that means a probable human carcinogen with sufficient evidence from animal studies but inadequate evidence from human studies. In most of the OECD countries the Hazardous air pollutants (HAPs) monitoring (Particularly the PAHs, BAP as an indicator species) and the risk assessment has become a regular feature. Integrated and long term monitoring is being carried out in the Netherlands Sweden, and the United States.
The world health organization (WHO) has already added PAHs into the list of the priority pollutants in both air and water. France, Japan, Germany, Netherlands Sweden and Switzerland have prescribed emission standards for most of HAPs including PAHs. The WHO and the Netherlands (WHO, 1987 & OECD, 1995) have even prescribed ambient air quality guidelines (AQG) for the PAHs ( Table: 23 )
Table - 23 : Ambient Air Quality Standard
for the PAHs
| Compound | Limit value | Guide value | Measuring Period |
| Netherlands PAH | 5 ng/m3 | .0.5 ng/m3 | Years as ng BAP/m3 |
| WHO-AQG PAH | 1.0 ng/m3 | Years as ng BAP/m3 |
Proposed new European Union ambient limits for PAH indicator parameter i.e. Benzo(a)pyrene is 6.0 ng/m3 for meeting on Ist January 2010. European Commission requires action plan to be developed to measure the concentration of Benzo(a)pyrene in ambient air & also to monitor other relevant PAH’s at limited number of sites. Other PAH compounds should include Benzo(a)pyrene, Benzo(b)flouranthene, Benzo(i)flouranthene, Benzo(k)flouranthene, Indeno(cd) pyrene , Dibenzo(ah)anthracene & Flouranthene. European Commission directive also recommends to set long term objective for containing the levels of these parameters.
According WHO (1987) , no safe level can be recommended for BaP due to its carcinogenicity. Complete removal of PAH from the environment is impossible, they can only be controlled. Therefore standard have to be set up. The primary basis for setting up such standards is the does-effect relationship, this can be fully demonstrated in PAH carcinogenesis and the result is extrapolated to man. On the basis of such evaluation, the USSR Ministry of Health set up the maximum allowable concentration (MAC) for BaP and it is recommended by FAO/WHO " joint Expert Committee". The MAC for Bap in the atmospheric air is proposal is 15 µg/100m3 for air of industrial working zones and 0.1 µg/100m3 in the atmospheric air. MAC for other PAHs are still to be set up.
WHO guidelines for drinking water (1984) have given PAH standard for water. In water of acceptable purity, the concentration of six representative PAH viz Fluoranthene, Benzo (b)fluoranthene, Benzo(k)fluoranthene. Benzo (a)pyrene, Benzo (ghi) perylene and Indeno (1,2,3 cd) pyrene should not collectively exceed 0,2 µg/lit this limit for Bap is 0.01 µg/lit as reported by Harrision et al. In the new European drinking water guideline (98/83/EC) also special attention is given to Benzo(a) pyrene by setting a threshold limit of 10 ng/l for this single compound.
Owing to its carcinogenicity no safe level of PAHs can be recommended. There is no known cancer threshold for B(a)P the most thoroughly studied PAH. (WHO, 1987). However The USEPA has offered an upper bound lifetime cancer risk estimate of 62 per 100000 exposed people per µg benzene soluble coke-oven emission per m3 ambient air. They are public health concern because they are spread over large urban population. The guidelines values for B(a)P corresponding to an excess lifetime cancer risk of 10-5 was estimated as 0.7mg/litre in Guideline for drinking water quality (WHO, 1998).
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