Bromoform (CHBr&lt
inf&gt
3&lt
/inf&gt
), dibromochloromethane (CHBr&lt
inf&gt
2&lt
/inf&gt
Cl), and dibromomethane (CH&lt
inf&gt
2&lt
/inf&gt
Br&lt
inf&gt
2&lt
/inf&gt
) in the atmosphere were measured at various sites, including tropical islands, the Arctic, and the open Pacific Ocean. Up to 40 ppt of bromoform was observed along the coasts of tropical islands under a sea breeze. Polybromomethane concentrations were highly correlated among the coastal samples, and the ratios CH&lt
inf&gt
2&lt
/inf&gt
Br&lt
inf&gt
2&lt
/inf&gt
/CHBr&lt
inf&gt
3&lt
/inf&gt
and CHBr&lt
inf&gt
2&lt
/inf&gt
Cl/CHBr&lt
inf&gt
3&lt
/inf&gt
showed a clear tendency to decrease with increasing CHBr&lt
inf&gt
3&lt
/inf&gt
concentration. These findings are consistent with the observations that polybromomethanes are emitted mostly from macroalgae whose growth is highly localized to coastal areas and that CHBr&lt
inf&gt
3&lt
/inf&gt
has the shortest lifetime among these three compounds. The relationship between the concentration ratios CHBr&lt
inf&gt
3&lt
/inf&gt
/CH&lt
inf&gt
2&lt
/inf&gt
Br&lt
inf&gt
2&lt
/inf&gt
and CHBr&lt
inf&gt
2&lt
/inf&gt
Cl/CH&lt
inf&gt
2&lt
/inf&gt
Br&lt
inf&gt
2&lt
/inf&gt
suggested a large mixing/dilution effect on bromomethane ratios in coastal regions and yielded a rough estimate of 9 for the molar emission ratio of CHBr&lt
inf&gt
3&lt
/inf&gt
/ CH&lt
inf&gt
2&lt
/inf&gt
Br&lt
inf&gt
2&lt
/inf&gt
and of 0.7 for that of CHBr&lt
inf&gt
2&lt
/inf&gt
Cl/CH&lt
inf&gt
2&lt
/inf&gt
Br&lt
inf&gt
2&lt
/inf&gt
. Using these ratios and an global emission estimate for CH&lt
inf&gt
2&lt
/inf&gt
Br&lt
inf&gt
2&lt
/inf&gt
(61 Gg/yr (Br)) calculated from its background concentration, the global emission rates of CHBr&lt
inf&gt
3&lt
/inf&gt
and CHBr&lt
inf&gt
2&lt
/inf&gt
Cl were calculated to be approximately 820(±310) Gg/yr (Br) and 43 (±16) Gg/yr (Br), respectively, assuming that the bromomethanes ratios measured in this study are global representative. The estimated CHBr&lt
inf&gt
3&lt
/inf&gt
emission is consistent with that estimated in a very recent study by integrating the sea-to-air flux database. Thus the contribution of CHBr&lt
inf&gt
3&lt
/inf&gt
and CHBr&lt
inf&gt
2&lt
/inf&gt
Cl to inorganic Br in the atmosphere is likely to be more important than previously thought. Copyright 2005 by the American Geophysical Union.