diff --git a/boards/cc2538dk/Makefile.include b/boards/cc2538dk/Makefile.include
index cca186c348..bdb3e9e2b5 100644
--- a/boards/cc2538dk/Makefile.include
+++ b/boards/cc2538dk/Makefile.include
@@ -35,4 +35,4 @@ FLASHFILE ?= $(BINFILE)
 DEBUGGER_FLAGS = $(BINDIR) $(ELFFILE)
 RESET_FLAGS ?= $(BINDIR)
 
-export OBJDUMPFLAGS += --disassemble --source --disassembler-options=force-thumb
+OBJDUMPFLAGS += --disassemble --source --disassembler-options=force-thumb
diff --git a/boards/common/msb-430/Makefile.include b/boards/common/msb-430/Makefile.include
index 4e1bf6426c..24db7f1355 100644
--- a/boards/common/msb-430/Makefile.include
+++ b/boards/common/msb-430/Makefile.include
@@ -20,5 +20,4 @@ DEBUGSERVER_FLAGS = $(MSPDEBUGFLAGS) gdb
 DEBUGGER = $(PREFIX)gdb
 DEBUGGER_FLAGS = --tui --ex="target remote localhost:2000" --ex "monitor reset halt" --ex load -ex "monitor reset halt"  $(ELFFILE)
 
-# export common msb-430 includes
-export INCLUDES += -I$(RIOTBOARD)/common/msb-430/include
+INCLUDES += -I$(RIOTBOARD)/common/msb-430/include
diff --git a/boards/common/msba2/Makefile.include b/boards/common/msba2/Makefile.include
index 8b5342698e..3216878da5 100644
--- a/boards/common/msba2/Makefile.include
+++ b/boards/common/msba2/Makefile.include
@@ -19,13 +19,13 @@ PORT_DARWIN ?= /dev/tty.usbserial-ARM
 TERMFLAGS += -tg -p "$(PORT)"
 include $(RIOTMAKE)/tools/serial.inc.mk
 
-export CFLAGS_CPU   = -mcpu=arm7tdmi-s
-export CFLAGS_LINK  = -ffunction-sections -fdata-sections -fno-builtin -fshort-enums
-export CFLAGS_DBG  ?= -ggdb -g3
-export CFLAGS_OPT  ?= -Os
+CFLAGS_CPU   = -mcpu=arm7tdmi-s
+CFLAGS_LINK  = -ffunction-sections -fdata-sections -fno-builtin -fshort-enums
+CFLAGS_DBG  ?= -ggdb -g3
+CFLAGS_OPT  ?= -Os
 
-export CFLAGS += $(CFLAGS_CPU) $(CFLAGS_LINK) $(CFLAGS_DBG) $(CFLAGS_OPT)
-export ASFLAGS += $(CFLAGS_CPU) $(CFLAGS_DBG)
+CFLAGS += $(CFLAGS_CPU) $(CFLAGS_LINK) $(CFLAGS_DBG) $(CFLAGS_OPT)
+ASFLAGS += $(CFLAGS_CPU) $(CFLAGS_DBG)
 export LINKFLAGS += -T$(RIOTCPU)/$(CPU)/ldscripts/$(CPU).ld
 export LINKFLAGS += $(CFLAGS_CPU) $(CFLAGS_DBG) $(CFLAGS_OPT) -static -lgcc -nostartfiles
 export LINKFLAGS += -Wl,--gc-sections
diff --git a/boards/common/remote/Makefile.include b/boards/common/remote/Makefile.include
index fd85d213aa..4d5c2a9944 100644
--- a/boards/common/remote/Makefile.include
+++ b/boards/common/remote/Makefile.include
@@ -23,10 +23,10 @@ endif
 OFLAGS = --gap-fill 0xff
 FLASHFILE ?= $(BINFILE)
 DEBUGGER_FLAGS = $(BINDIR) $(ELFFILE)
-export OBJDUMPFLAGS += --disassemble --source --disassembler-options=force-thumb
+OBJDUMPFLAGS += --disassemble --source --disassembler-options=force-thumb
 
 # include common remote includes
-export INCLUDES += -I$(RIOTBOARD)/common/remote/include
+INCLUDES += -I$(RIOTBOARD)/common/remote/include
 
 # setup serial terminal
 include $(RIOTMAKE)/tools/serial.inc.mk
diff --git a/boards/common/silabs/Makefile.include b/boards/common/silabs/Makefile.include
index f62e5fec7f..b3880891b6 100644
--- a/boards/common/silabs/Makefile.include
+++ b/boards/common/silabs/Makefile.include
@@ -1,2 +1,2 @@
-export INCLUDES += -I$(RIOTBOARD)/common/silabs/include
-export INCLUDES += -I$(RIOTBOARD)/common/silabs/drivers/include
+INCLUDES += -I$(RIOTBOARD)/common/silabs/include
+INCLUDES += -I$(RIOTBOARD)/common/silabs/drivers/include
diff --git a/boards/common/wsn430/Makefile.include b/boards/common/wsn430/Makefile.include
index 57881a1e99..8fa4aa992c 100644
--- a/boards/common/wsn430/Makefile.include
+++ b/boards/common/wsn430/Makefile.include
@@ -1,7 +1,7 @@
 # include this module in the build
 USEMODULE += boards_common_wsn430
 # use common wsn430 includes
-export INCLUDES += -I$(RIOTBOARD)/common/wsn430/include
+INCLUDES += -I$(RIOTBOARD)/common/wsn430/include
 
 # configure the serial interface
 PORT_LINUX ?= /dev/ttyUSB0
diff --git a/boards/hamilton/Makefile.include b/boards/hamilton/Makefile.include
index b253623185..c88822cb9d 100644
--- a/boards/hamilton/Makefile.include
+++ b/boards/hamilton/Makefile.include
@@ -1,7 +1,7 @@
 # debugger config
 export JLINK_DEVICE := atsamr21e18a
-export OBJDUMPFLAGS += --disassemble --source --disassembler-options=force-thumb
-export OFLAGS := --gap-fill 0xff
+OBJDUMPFLAGS += --disassemble --source --disassembler-options=force-thumb
+OFLAGS := --gap-fill 0xff
 
 # Configure terminal, hamilton doesn't provide any UART, thus use RTT
 TERMPROG = $(RIOTTOOLS)/jlink/jlink.sh
diff --git a/boards/native/Makefile.include b/boards/native/Makefile.include
index 19ad94aae1..8714775def 100644
--- a/boards/native/Makefile.include
+++ b/boards/native/Makefile.include
@@ -21,30 +21,30 @@ export CGANNOTATE ?= cg_annotate
 export GPROF ?= gprof
 
 # basic cflags:
-export CFLAGS += -Wall -Wextra -pedantic
+CFLAGS += -Wall -Wextra -pedantic
 # default std set to gnu99 of not overwritten by user
 ifeq (,$(filter -std=%, $(CFLAGS)))
-  export CFLAGS += -std=gnu99
+  CFLAGS += -std=gnu99
 endif
 
 ifeq ($(shell uname -m),x86_64)
-  export CFLAGS += -m32
+  CFLAGS += -m32
 endif
 ifneq (,$(filter -DDEVELHELP,$(CFLAGS)))
-  export CFLAGS += -fstack-protector-all
+  CFLAGS += -fstack-protector-all
 endif
 ifeq ($(shell uname -s),FreeBSD)
   ifeq ($(shell uname -m),amd64)
-    export CFLAGS += -m32 -DCOMPAT_32BIT -B/usr/lib32
+    CFLAGS += -m32 -DCOMPAT_32BIT -B/usr/lib32
   endif
 endif
 ifeq ($(shell uname -s),Darwin)
-  export CFLAGS += -Wno-deprecated-declarations
+  CFLAGS += -Wno-deprecated-declarations
 endif
 
 # unwanted (CXXUWFLAGS) and extra (CXXEXFLAGS) flags for c++
-export CXXUWFLAGS +=
-export CXXEXFLAGS +=
+CXXUWFLAGS +=
+CXXEXFLAGS +=
 
 ifeq ($(shell uname -m),x86_64)
   export LINKFLAGS += -m32
@@ -59,7 +59,7 @@ else
 endif
 
 # clean up unused functions
-export CFLAGS += -ffunction-sections -fdata-sections
+CFLAGS += -ffunction-sections -fdata-sections
 ifeq ($(shell uname -s),Darwin)
   export LINKFLAGS += -Wl,-dead_strip
 else
@@ -76,7 +76,7 @@ endif
 
 TERMFLAGS := $(PORT) $(TERMFLAGS)
 
-export ASFLAGS =
+ASFLAGS =
 ifeq ($(shell basename $(DEBUGGER)),lldb)
   DEBUGGER_FLAGS = -- $(ELFFILE) $(TERMFLAGS)
 else
@@ -92,23 +92,23 @@ debug-valgrind-server: export VALGRIND_FLAGS ?= --vgdb=yes --vgdb-error=0 -v \
 	--read-var-info=yes
 term-cachegrind: export CACHEGRIND_FLAGS += --tool=cachegrind
 term-gprof: TERMPROG = GMON_OUT_PREFIX=gmon.out $(ELFFILE)
-all-valgrind: export CFLAGS += -DHAVE_VALGRIND_H -g3
+all-valgrind: CFLAGS += -DHAVE_VALGRIND_H -g3
 all-valgrind: export NATIVEINCLUDES += $(shell pkg-config valgrind --cflags)
-all-debug: export CFLAGS += -g3
-all-cachegrind: export CFLAGS += -g3
-all-gprof: export CFLAGS += -pg
+all-debug: CFLAGS += -g3
+all-cachegrind: CFLAGS += -g3
+all-gprof: CFLAGS += -pg
 all-gprof: export LINKFLAGS += -pg
-all-asan: export CFLAGS += -fsanitize=address -fno-omit-frame-pointer -g3
-all-asan: export CFLAGS += -DNATIVE_IN_CALLOC
+all-asan: CFLAGS += -fsanitize=address -fno-omit-frame-pointer -g3
+all-asan: CFLAGS += -DNATIVE_IN_CALLOC
 all-asan: export LINKFLAGS += -fsanitize=address -fno-omit-frame-pointer -g3
 
-export INCLUDES += $(NATIVEINCLUDES)
+INCLUDES += $(NATIVEINCLUDES)
 
-export CFLAGS += -DDEBUG_ASSERT_VERBOSE
+CFLAGS += -DDEBUG_ASSERT_VERBOSE
 
 # workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52624
 ifneq ($(shell gcc --version | head -1 | grep -E ' (4.6|4.7)'),)
-  export CFLAGS += -DHAVE_NO_BUILTIN_BSWAP16
+  CFLAGS += -DHAVE_NO_BUILTIN_BSWAP16
 endif
 
 # backward compatability with glibc <= 2.17 for native
diff --git a/boards/openmote-b/Makefile.include b/boards/openmote-b/Makefile.include
index d1c835b127..5f37a86536 100644
--- a/boards/openmote-b/Makefile.include
+++ b/boards/openmote-b/Makefile.include
@@ -26,7 +26,7 @@ else ifeq ($(PROGRAMMER),jlink)
   include $(RIOTMAKE)/tools/jlink.inc.mk
 endif
 
-export OBJDUMPFLAGS += --disassemble --source --disassembler-options=force-thumb
+OBJDUMPFLAGS += --disassemble --source --disassembler-options=force-thumb
 
 # setup serial terminal
 include $(RIOTMAKE)/tools/serial.inc.mk
diff --git a/boards/saml10-xpro/Makefile.include b/boards/saml10-xpro/Makefile.include
index 34d32c3383..e33947745c 100644
--- a/boards/saml10-xpro/Makefile.include
+++ b/boards/saml10-xpro/Makefile.include
@@ -1,4 +1,4 @@
 export CPU_FAM  = saml10
-export CFLAGS += -D__SAML10E16A__
+CFLAGS += -D__SAML10E16A__
 
 include $(RIOTBOARD)/common/saml1x/Makefile.include
diff --git a/boards/saml11-xpro/Makefile.include b/boards/saml11-xpro/Makefile.include
index 59e407b0e1..c24adbef10 100644
--- a/boards/saml11-xpro/Makefile.include
+++ b/boards/saml11-xpro/Makefile.include
@@ -1,4 +1,4 @@
 export CPU_FAM  = saml11
-export CFLAGS += -D__SAML11E16A__
+CFLAGS += -D__SAML11E16A__
 
 include $(RIOTBOARD)/common/saml1x/Makefile.include
diff --git a/boards/saml21-xpro/Makefile.include b/boards/saml21-xpro/Makefile.include
index 4ccc713f7d..56e111043a 100644
--- a/boards/saml21-xpro/Makefile.include
+++ b/boards/saml21-xpro/Makefile.include
@@ -1,4 +1,4 @@
-export CFLAGS += -D__SAML21J18A__
+CFLAGS += -D__SAML21J18A__
 
 # set edbg device type
 EDBG_DEVICE_TYPE = atmel_cm0p
diff --git a/boards/slwstk6000b/Makefile.include b/boards/slwstk6000b/Makefile.include
index fcb83ee567..7993d0d7ce 100644
--- a/boards/slwstk6000b/Makefile.include
+++ b/boards/slwstk6000b/Makefile.include
@@ -1,7 +1,7 @@
 include $(RIOTBOARD)/slwstk6000b/module-info.mk
 
 # add module specific includes
-export INCLUDES += -I$(RIOTBOARD)/slwstk6000b/modules/$(BOARD_MODULE)/include
+INCLUDES += -I$(RIOTBOARD)/slwstk6000b/modules/$(BOARD_MODULE)/include
 
 # define the cpu used by SLWSTK6000B
 export CPU = efm32