Although the rules for determining dose to individuals exposed to the smoke plume from a burning warehouse containing agrochemicals have been defined, their application presents problems for practical situations.
There are several ways in which doses from different pesticides can be added, but given the uncertainty attached to all of them, perhaps the best choice is the one involving the least amount of effort. The Agrochemicals Handbook lists 204 different types of pesticide, all of which presumably have a different effect on the body. However there are 86 listed organophosphorous compounds and these are known to be the most toxic of all pesticides. Other groups which have a large number of members and are relatively toxic include: -
Table 10: Number of pesticides in 4 typical groups
|
Type |
No. |
Example |
|---|---|---|
|
Organophosphorus |
70 |
chlorfenvinphos, chlorpyrifos, dichlovos |
|
Carbamates |
45 |
aldicarb, pirimicarb, carbofuran |
|
Organochlorides |
45 |
lindane, heptachlor, endosulphan |
|
Pyrethoids |
29 |
cyhalothrin, esfenvalerate, cypermethrin |
There are other agrochemicals that are particularly toxic but, which have few class members, these include bipyridyls such as paraquat and coumarins such as warfarin and difenacoum. These need to be considered separately.
It is recommended that when carrying out warehouse safety assessment, all members of each of the above 5 classes are added together according to the following prescription: -
where
| A | = | toxic load to produce a dangerous dose in mg/m^3.mins |
| Amost toxic | = | toxic load to produce a dangerous dose |
| RF | = | release fraction |
| RF most toxic | = | release fraction of the most toxic |
This approach is applied to the warehouse inventory shown in Table 11.
Table 11: Warehouse inventory - hazard data
|
Active ingredient |
Total mass kg |
HSE-A value ppm.min |
Dang. dose ppm.min |
Mol Wt |
LD50 |
Dang. conc. mg/m3 |
Release fraction |
Mass released |
Hazard ndex |
|---|---|---|---|---|---|---|---|---|---|
|
Chlorpyrifos |
60,000 |
3,600 |
811 |
350.6 |
135 |
394.2 |
0.1 |
6,000 |
15.22 |
|
Bifenthrin |
1,250 |
271 |
422.9 |
54.5 |
159.1 |
0.1 |
125 |
0.79 |
|
|
Cyanazine |
2,137.5 |
1,234 |
240.7 |
141 |
411.7 |
0.1 |
213.75 |
0.52 |
|
|
Triclopyr |
3,000 |
2,545 |
256.5 |
310 |
905.2 |
0.1 |
300 |
0.33 |
|
|
Imazalil |
625 |
2,268 |
297.2 |
320 |
934.4 |
0.1 |
62.5 |
0.07 |
|
|
Cypermetherin |
1,250 |
698 |
416.3 |
138 |
403 |
0.1 |
125 |
0.31 |
|
|
Lindane |
25,000 |
2,650 |
427 |
290.9 |
59 |
172.3 |
0.1 |
2,500 |
14.51 |
|
Paraquat |
50,000 |
11 |
360 |
186.3 |
93 |
0.1 |
187.5 |
53.76 |
|
|
Phorate |
3,750 |
15 |
19 |
260.4 |
7 |
0.05 |
26.79 |
||
|
Chlorfenvinfos |
15,000 |
201 |
141 |
359.6 |
24 |
70.1 |
0.1 |
1,500 |
21.4 |
|
Ioxynil |
2,812.5 |
4,250 |
625 |
370.9 |
110 |
321.2 |
0.1 |
281 |
0.88 |
|
Fonofos |
3,437.5 |
94 |
246.3 |
11 |
32.1 |
0.1 |
343.75 |
10.7 |
|
|
Diquat |
1,000 |
1,429 |
184.2 |
125 |
365 |
0.04 |
40 |
0.11 |
|
|
Dichlorvos |
625 |
85 |
534 |
221 |
56 |
163.5 |
0.1 |
62.5 |
0.38 |
|
Carbophenothion |
2,500 |
61 |
343 |
10 |
29.2 |
0.1 |
250 |
8.56 |
|
|
Pirimicarb |
1,875 |
8,830 |
972 |
238.3 |
110 |
321.2 |
0.05 |
93.75 |
0.29 |
Noting that phorate is the most toxic organophosphorus pesticide, paraquat is the most toxic bipyridyl and lindane the most toxic organochlorine. Table 12 illustrates how Effective Masses for each pesticide in the three dominant groups can be calculated.
The problem now reduces to assessing the hazard from releases of three pesticides: -
| Substance | Mass | Release fraction |
|---|---|---|
| phorate | 11,628 | 0.05 |
| lindane | 25,571 | 0.1 |
| paraquat | 50,102 | 0.1 |
Table 12: Hazard assessment sheet
|
Active |
Type |
Total mass kg |
Dang. Conc. mg/m3 |
Release fraction |
Effective mass |
|---|---|---|---|---|---|
|
Chlorpyrifos |
Organophosphorus |
60,000 |
394.2 |
0.1 |
2,130.9 |
|
Bifenthrin |
Pyrethroid |
1,250 |
159.1 |
0.1 |
|
|
Cyanazine |
triazine |
2,137.5 |
411.7 |
0.1 |
|
|
Triclopyr |
Organochlorine |
3,000 |
905.2 |
0.1 |
571.03 |
|
Imazalil |
Imidazole |
625 |
934.4 |
0.1 |
|
|
Cypermetherin |
Pyrethroid |
1,250 |
403 |
0.1 |
|
|
Lindane |
Organochlorine |
25,000 |
172.3 |
0.1 |
25,000 |
|
Paraquat |
Bipyridyl |
50,000 |
93 |
0.1 |
50,000 |
|
Phorate |
Organophosphorus |
3,750 |
7 |
0.05 |
3,750 |
|
Chlorfenvinfos |
Organophosphorus |
15,000 |
70.1 |
0.1 |
2,995.72 |
|
Ioxynil |
Nitrile |
2,812.5 |
321.2 |
0.1 |
|
|
Fonofos |
Organophosphorus |
3,437.5 |
32.1 |
0.1 |
1,499.22 |
|
Diquat |
Bipyridyl |
1,000 |
365 |
0.04 |
101.92 |
|
Dichlorvos |
Organophosphorus |
625 |
163.5 |
0.1 |
53.52 |
|
Carbophenothion |
Organophosphorus |
2,500 |
29.2 |
0.1 |
1,198.63 |
|
Pirimicarb |
Carbamate |
1,875 |
321.2 |
0.05 |
| Organochlorine (Lindane) | 25571.034 |
| Bipyridyl (Paraquat) | 50101.918 |
| Organophosphorus (Phorate) | 11627.987 |