diff --git a/src/pyaro_readers/eeareader/EEATimeseriesReader.py b/src/pyaro_readers/eeareader/EEATimeseriesReader.py
index edcb593..5e7de53 100644
--- a/src/pyaro_readers/eeareader/EEATimeseriesReader.py
+++ b/src/pyaro_readers/eeareader/EEATimeseriesReader.py
@@ -174,6 +174,9 @@ def _read_polars(self, filters, filename) -> None:
                     continue
 
                 file_unit = self._convert_unit(df.row(0)[df.get_column_index("Unit")])
+                if s in self.datafile["changeunit"]:
+                    file_unit = self.datafile["changeunit"][s]["unit"]
+                    df.with_columns((polars.col(PARQUET_FIELDS["values"]) * self.datafile["changeunit"][s]["factor"]).alias(PARQUET_FIELDS["values"]))
 
                 for key in PARQUET_FIELDS:
                     array[key][
diff --git a/src/pyaro_readers/eeareader/data.toml b/src/pyaro_readers/eeareader/data.toml
index d4aed9e..89164f2 100644
--- a/src/pyaro_readers/eeareader/data.toml
+++ b/src/pyaro_readers/eeareader/data.toml
@@ -62,6 +62,8 @@
 "ugso2.m-3" = "µg SO2/m3"
 "nm" = "nm"
 
+[changeunit]
+"SO4--" = { unit = "µg /m3", factor = 2995.82 }
 
 [pollutant]
 1 = "SO2"
diff --git a/src/pyaro_readers/eeareader/utils/generate_data_toml.py b/src/pyaro_readers/eeareader/utils/generate_data_toml.py
index 2f67098..3e72c3b 100644
--- a/src/pyaro_readers/eeareader/utils/generate_data_toml.py
+++ b/src/pyaro_readers/eeareader/utils/generate_data_toml.py
@@ -31,6 +31,10 @@
     "HNO3",
 ]
 
+changeunit = {
+    "SO4--" : '{ unit = "µg /m3", factor = 2995.82 }'
+}
+
 with open("response.json", "r") as f:
     properties = {}
     data = json.load(f)
@@ -56,6 +60,11 @@
         target.write(f'"{poll}",\n')
     target.write("]\n\n")
 
+    target.write('[changeunits]\n')
+    for s in changeunit:
+        target.write(f'"{s}" = {changeunit[s]}\n')
+    target.write("]\n\n")
+
     target.write("[units]\n")
     for key in response:
         target.write(f'"{key.lower()}" = {response[key]}\n')